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Chapter 7
Organic Cultivation
of Citrus (Citrus spp.)
Heiplanmi Rymbai
Division of System Research and Engineering, ICAR Research Complex for NEH
Region, Ri Bhoi, Umiam–793103, Meghalaya, India
1. Introduction
Citrus trees (Citrus spp.) are considered one of the most important fruit crops
in 140 different countries worldwide. Fresh fruit for the market is preferably
produced in subtropical and Mediterranean climates, while citrus for juice is
predominant in tropical climates because of the possibility of higher sugar
content (FiBL 2011). Citrus products labelled “organic” are those that have
been certied organically throughout the production process. An independent
organisation (usually known as a certification agency) recognised by an
authority validates the grower’s compliance with these standards (e.g., the
national authority in the producing or importing country). Since 1970, organic
foods have gained interest on a global scale. Today, many farmers implement
organic practices to attract consumers and increase their income. In turn, these
agronomic practices promote crop rotation, biodiversity, etc., and the ban of
synthetic pesticides and fertilisers (Reganold and Wachter, 2016). However,
despite the fact that organic systems produce smaller volumes of food, it has
been shown that organic foods are more nutritious than conventional ones,
presenting higher contents of vitamin C or total antioxidants, among other things
(Sanchez Bravo et al., 2022). In general, organic farming is considered to be more
Citation
Rymbai, H. 2024. Organic Cultivation of Citrus (Citrus spp.). In: Organic
Culture of Tropical and Subtropical Fruit Plants (Eds. Ghosh, S.N., Krishna Hare,
Rymbai, H). Publisher Gyanavi Publishers & Distributors. ISBN
978-81-960111-5-4. pp 131-176. doi: 10.13140/RG.2.2.36585.51049
Organic Culture of Tropical and Subtropical Fruit Plants
132 |
respectful of the environment than conventional farming since it reduces the use
of chemical fertilizers and pesticides, although the use of some non-synthetic
pesticides, such as sulphur, copper sulphate, potassium permanganate, etc., is
allowed in a restricted manner.
Organic citrus is still considered a niche commodity, accounting for
approximately 1–2 per cent of global citrus production (Kilcher, 2005) and
0.6 per cent of global citrus acreage (FAOSTAT, 2009). In EU, the total area
devoted to organic farming continues to increase, covering almost 13.8 million
hectares of agricultural land (EUROSTAT 2021). In Europe, the share of organic
citrus was 5.3 per cent of the total citrus area in 2011. About 74 per cent of
the total area under organic citrus cultivation was devoted to oranges, 15 per
cent to mandarins, 10 per cent to lemons, and 1 per cent to other citrus fruits
(EUROSTAT, 2012). The main areas for organic citrus production are Latin and
North America, Europe, and the Near East, and many tropical countries in the
Americas, in particular, are expanding their production (Kilcher, 2005). The
organic citrus acreage in the EU-27 has increased in all thesouthern European
countries to 28,000 ha (Willer and Kilcher, 2009). The organic production of
citrus juice has also been increasing in demand, with Brazil (1.4 million tons)
and the United States (0.6 million tons) being the two major producers (USDA
Citrus Update, 2011). Organic citrus imports into Europe increased by 31.3 per
cent in 2020 compared to 2019 (EUROSTAT, 2021).
India ranked rst in the world in terms of organic farmers and fth in terms
of organic agricultural land, accounting for 44 per cent of the world’s certied
organic growers (FIBL and IFOAM Year Book, 2020, APEDA website). Despite
its large number of certied organic farmers, India’s overall certied organic
cultivated area (2.3 million hectares) contributes only 3 per cent of the global
total area (72.3 million hectares) under organic cultivation. In addition to high
domestic demand for organic citrus, the import of organic citrus fruit into
European markets has also increased by 31.3 per cent in 2020. Almost half of the
imported organic citrus fruit originates from South Africa (43 per cent),while
other organic fruits come mainly from Turkey (25 per cent), Argentina (15 per
cent), and Ukraine (12 per cent) (EUROSTAT, 2021). The contribution of Indian
citrus industries to the international market is still negligible. Therefore, there is
scope for area and production expansion with quality improvement to capture
the international market’s demands.
2. Nutritional Composition of Organically grown Citrus
Fruits
Mandarin Orange
The effect of the production system on fruit quality is well established in
citrus fruits. Organic systems had higher fruit weight (82.1 g) and diameter
(83.5 mm) as compared to conventional practices, which were higher in organic
Organic Cultivation of Citrus (Citrus spp.) | 133
fruits. The colour coordination of organic “Clemenules” mandarins (fruit juices)
was not statistically different from that of conventional agricultural conditions.
However, fruit juices from organic practices presented the higher values of
lightness: L* (53.26), a* (9.21), b* (29.93), and C* (31.31), with the exception of
hab (73.89) (Perez-Lopez et al., 2007).
The mineral nutrient content of mandarin fruits was signicantly higher
in the organic production system over conventional: Ca (43.80 vs. 39.80 mg/L),
Mg (133 vs. 120 mg/L), K (1584 vs. 1416 mg/L), Na (6.54 vs. 4.42 mg/L), Fe
(0.58 vs. 0.48 mg/L), Cu (0.35 vs. 0.23 mg/L), Mn (0.16 vs. 0.12 mg/L), and Zn
(0.44 vs. 0.27 mg/L) (Perez-Lopez et al., 2007).
In mandarin fruits, citric acid is the most abundant organic acid, while
in the case of “Setubalense” mandarin, it was tartaric acid. The organic acid
concentration in the juice of 18 citrus cultivars belongs to the mandarin, orange,
and lemon groups, as determined by Duarte et al. (2010) who found that the
concentration of citric acid was higher in fruits from organic production. Only
in “Fortune” mandarins was the concentration of citric acid higher in fruits
from conventional agriculture.
Out of 11 cultivars of mandarin, nine had higher ascorbic acid concentrations
in the organically grown fruits. However, in the two hybrids (Citrus deliciosa
and Citrus nobilis), viz., “Encore” (conventional, 7.4 vs. organic, 3.4 mg/100 ml)
and “Wilking” (conventional, 17.5 vs. organic, 8.1 mg/100 ml), the opposite was
true (Perez-Lopez et al., 2007).
The volatile compounds, organic acids, and sugars, and their relationships,
are the specic characteristics of citrus fruit quality. The volatile compounds
of “Clemenules” juices were higher under organic production (83.1±2.1 mg/L)
than under conventional production system (61.1±1.8 mg/L) (Table 7.1). On
storage, conventional juice had a higher reduction (47.5 per cent) of volatile
compounds than organic juice (38.5 per cent). Besides, the formation of off-
avour compounds was lower in the organic juice compared to the conventional
one. Therefore, organic farming had a positive effect on the quality and stability
of mandarin juices.
Table 7.1: Effect of Organic and Conventional Production System on
“Clemenules” Mandarins
Characteristics Organic Cultivation Conventional Cultivation
Quality attributes
Fruit weight (g) 82.1 80.1
Fruit diameter (mm) 83.5 82.4
Vitamin C (mg L–1) 514.2 483.3
Soluble solid content (oBrix) 12.5 12.2
Titratable acidity (per cent citric acid) 0.94 0.89
Organic Culture of Tropical and Subtropical Fruit Plants
134 |
Characteristics Organic Cultivation Conventional Cultivation
Maturity index (SSC/TA) 13.3 13.6
L
”53.26 53.02
a”9.21 8.57
b”29.93 29.40
C”31.31 30.63
“hab 72.89 73.75
Mineral compositions
Ca 43.80 39.80
Mg 133.0 120.0
K 1584 1416
Na 6.54 4.42
Fe 0.58 0.48
Cu 0.35 0.23
Mn 0.16 0.12
Zn 0.44 0.27
Volatile compounds
α-Pinene 0.35 0.20
β-Pinene 0.12 0.08
Myrcene 1.71 1.03
α-Terpinene 0.11 0.01
d-Limonene 77.2 59.2
Sabinene 1.21 0.18
γ -Terpinene 0.86 0.05
p-Cymene 0.55 0.11
α-Terpineol n.d n.d
Valencene 0.63 a 0.07
Terpinen-4-ol n.d 0.03
Linalool 0.37 0.17
Total 83.11 61.13
Source: Perez Lopez et al. (2007).
Lemon
In lemon(cv. “Fino 49”), the fruit weight (121.75 g), fruit equatorial
diameter (58.35 mm), and fruit polar diameter (79.66 mm) were higher under
the conventional system than fruits grown organically, as given in Table 7.2
(Sanchez-Bravo et al., 2022). Similarly, there were no signicant differences in
the colour of the lemon (peel and juice), except for the lightness parameter (L*),
in which conventional lemons presented the highest values (73.38) (Table 7.3).
Organic Cultivation of Citrus (Citrus spp.) | 135
Table 7.2: Physico-Biochemical, Organic Acids, Sugars and Volatile Compounds
of Lemon cv. Fino 49 under Organic and Conventional Orcharding
Parameters Conventional Organic
Fruit weight (g) 121.75 106.17
Fruit equatorial diameter (mm) 58.35 56.32
Fruit polar diameter (mm) 79.66 72.34
Peel thickness (mm) 5.53 5.14
Total soluble solids (oBrix) 9.77 8.77
pH 2.94 2.91
Titratable acidity (g citric acid/L) 64.39 57.27
Malic (g/L) 0.48 0.27
Citric (g/L) 6.04 5.45
Succinic (g/L) 0.61 0.56
Glucose (g/L) 10.67 9.49
Fructose (g/L) 5.50 4.93
3-Heptanone (mg/L) 3.81 2.98
α-Pinene (mg/L) 8.48 11.54
β-Pinene (mg/L) 22.06 27.18
β-Myrcene (mg/L) 32.25 57.63
α-Phellandrene (mg/L) 1.07 1.19
α-Terpinene(mg/L) 6.50 8.72
p-Cymene (mg/L) 10.62 13.04
Limonene (mg/L) 1086 1310
trans- β-Ocimene (mg/L) 4.72 5.96
γ-Terpinene(mg/L) 188.49 252.85
1-Octanol (mg/L) 6.80 5.54
Terpinolene (mg/L) 36.07 48.91
Linalool (mg/L) 77.82 35.18
Nonanal (mg/L) 13.05 19.18
D-Fenchyl alcohol (mg/L) 8.62 13.41
Citronellal (mg/L) 3.28 4.14
1-Nonanol (mg/L) 13.81 13.40
Borneol (mg/L) 2.45 4.29
Terpinen-4-ol (mg/L) 72.28 84.48
α-Terpineol (mg/L) 143.26 198.45
Decanal (mg/L) 6.13 7.23
Nerol(mg/L) 149.61 62.06
Neral(mg/L) 5.39 3.41
Geraniol (mg/L) 162.47 59.99
Organic Culture of Tropical and Subtropical Fruit Plants
136 |
Parameters Conventional Organic
Geranial (mg/L) 10.35 8.52
Citronellyl acetate (mg/L) 3.71 2.83
Neryl acetate(mg/L) 111.84 82.15
Geranyl acetate(mg/L) 47.60 20.39
trans-Caryophyllene(mg/L) 1.57 2.31
trans-α-Bergamotene(mg/L) 2.68 17.73
α-Farnesene(mg/L) 0.55 2.08
β-Bisabolene(mg/L) 8.10 37.36
Total (mg/L) 2406 2537
Source: Sanchez-Bravo et al. (2022).
Table 7.3: Color Analysis of Lemon Peel and Lemon Juice under
Organic and Conventional Orcharding
Systems L* a* b* C* h CCI
Peel
Conventional 73.38 -4.42 58.49 59.06 83.37 -1.26
Organic 70.92b -5.88 56.73 57.55 82.21 -1.74
Anova * ns ns ns ns ns
Juice
Conventional 30.77 -1.31 -0.23 1.34 10.72 322.3
Organic 33.44 -1.48 0.17 1.51 10.63 15.27
Anova ns ns ns ns ns ns
L* (lightness), a* (green-red coordinate) and b* (blue-yellow coordinate), C* (Chroma) and
h (tone), CCI (Citrus Color Index = 1000 a*/L*b*)).
Source: Sanchez-Bravo et al. (2022).
Colour is considered a determining factor by the consumer in the purchase
of lemons. This colour change occurs due to the degradation of chlorophylls
present in the peel and the synthesis of carotenoids, which provide the yellow
colour to citrus fruits (Manera et al., 2012). In lemon, the relationship between
the concentration of sugars and organic acids is the main cause of its avour
(Serna-Escolano et al., 2021). Total soluble solids (TSS), pH, and total titratable
acidity (TA) of the lemons grown under conventional and organic farming were
analysed by Perez-Lopez et al. (2007). In general, the avour of citrus fruits
is highly inuenced by the level of TSS and organic acids. In addition, TA is
used as an indicator of the quality of juices. Organic lemons had a lower TSS
(8.77o Brix) and total titratable acidity (57.27 g citric acid/L) concentration than
lemons grown in a conventional way (9.77o Brix and 64.39 g citric acid/L). Sugars
Organic Cultivation of Citrus (Citrus spp.) | 137
(glucose and fructose) and organic acids (malic, citric, and succinic) of lemon
grown under organic conditions presented a lower concentration of glucose (9.49
g/L) and fructose (4.93 g/L) than conventional (glucose, 10.67 g/L; fructose, 5.50
g/L). Similarly, organic acids such as malic acid (0.27 g/L), citric acid (5.45 g/L),
and succinic acid (0.56 g/L) were higher under conventional cultivation (malic
acid, 0.48 g/L; citric acid, 6.04 g/L; succinic acid, 0.65 g/L). Serna-Escolano et
al. (2021) also opined that the relationship between the concentration of sugars
and organic acids is the main cause of the avor in lemon.Similar patterns
were observed for citric acid and tartaric acid in lemon “Lisbon” by Duarte et
al. (2010). However, it was contradictory with regards to malic acid, ascorbic
acid, melonic acid, and oxalic acid, which were higher under the organic system
than the conventional system in Lemon “Lisbon”.
In the lemon cultivar Lisbon, there are non-statistically significant
differences in ascorbic acid. The concentration of malic acid in fruits from
organic farming was higher in most cultivars; the exceptions were the Fortune
mandarin and Rohde orange. The concentration of tartaric acid had no signicant
differences between the two modes of production in many cultivars. However,
the tartaric acid of organic farming was statistically superior in cultivars “Nova,”
“Fremont,” “Fina,” “Rohde,” ‘Baía’ and “Dalmau” (Duarte et al., 2010).
Volatile compounds of lemon juice (32 no.) and peel oils (34 no.) were
identied (Table 7.1) in organically grown lemon (Sanchez-Bravo et al., 2022).
The three most abundant compounds in lemon juice were found to be limonene
(1310 and 1086 mg/L, organic and conventional, respectively), -terpinene (252.85
and 188.49 mg/L, organic and conventional, respectively), and -terpineol (198.45
and 143.26 mg/L, organic and conventional, respectively).
On the other hand, the major compounds in the essential oil of the peel were
limonene (15,893 and 16,953 mg/L for organic and conventional, respectively),
-myrcene (3060 and 2911 mg/L for organic and conventional, respectively), and
-terpinene (2073 and 1797 mg/L for organic and conventional, respectively).
These compounds have a marked aroma of grape, fruity, peach, lemon, orange,
citrus, and herbaceous (Navarro-Martinez et al., 2019), which gives a complex
and attractive odour and aroma to this fruit. It was concluded that both in
the juice and peel (essential oil), organically grown lemons have a higher
concentration of key aromatic compounds, except for limonene in the essential
oil, which was higher in the conventional samples. Furthermore, the content of
volatile compounds present in the juice and essential oil of the peel is slightly
inuenced by agronomic practices.
Sensory quality has a key inuence on how consumers perceive the quality
of a product and on their preferences (Green-Petersen, 2010). The consumers’
preferences for the organic lemon juices were higher for their odour (28 per cent),
avour (67 per cent), sourness (44 per cent), and overall liking (global) attributes.
The higher preferences were correlated with volatile compounds. Similarly, for
overall liking (global), consumers preferred organic samples. The organically
Organic Culture of Tropical and Subtropical Fruit Plants
138 |
grown lemons were sourer than those grown conventionally. This may be due
to the fact that the total acid/sugar ratio is higher in organic fruits, in addition
to their higher acidity. King et al. (2007) showed that small changes in sensory
sourness can cause cognitive associations that lead consumers to associate
this change with greater intensities of fruity and citrus avors. Sourness is the
sensory characteristic most appreciated by consumers in lemons, so it is justied
that a higher perception of acidity is related to a higher degree of satisfaction
(Sanchez-Bravo et al., 2022).
Grape Fruit
Citrus fruits grown on organic farms had a higher juice percentage as well
(Lester et al., 2007). However, the skin thickness was less in organic fruits (5.14
mm) (Tables 7.4–7.9).
Table 7.4: Whole-Fruit Market Quality Attributes of Conventional vs
Organic Rio Red Grapefruit
Production
System
Fruit
Weight
(g)
Fruit
Specific
Gravity
Peel
Thickness
(mm)
Peel Color Characteristics
Lightness Chroma Hueo
Conventional 466 0.88 59.3 66.7 45.1 68.7
Organic 457 0.92 49.5 69.0 44.4 74.3
Lightness or darkness (+100 = white, -100 = black), chroma (+ = color intensity), and hueo
or color (0o = red, 90o = yellow, 180o = green, and 270o = blue). fw, fresh weight.
Source: Lester et al. (2007).
Table 7.5: Internal Fruit Market Quality Attributes of Conventional vs
Organic Rio Red Grapefruit
Production
System
Juice
(per cent)
Juice Color Characteristicsb
Lightness Chroma Hueo
Conventional 39.9 37.3 13.2 35.5
Organic 42.6 39.7 11.5 45.8
Lightness or darkness (+100 = white, -100 = black), chroma (+ = color intensity), and hueo
or color (0o = red, 90o = yellow, 180o = green, and 270o = blue).
Table 7.6: Juice Mineral Analyses of Conventional vs
Organic Rio Red Grapefruit Juice
Production
System
Total
N (%)
Cl
(%)
ppm
P K B Ca Cu Fe Mg Mn Na Zn
Conventional 0.106 0.50 132 1309 15.7 102 1.4 4.1 86 2.4 64 0.8
Organic 0.072 0.43 145 1246 17.8 44 1.2 7.0 85 2.5 61 0.6
On a fresh weight basis.
Organic Cultivation of Citrus (Citrus spp.) | 139
Table 7.7: Ascorbic Acid, Lycopene, Sugars, and Pectin in
Conventional vs Organic Rio Red Grapefruit
Production
System
Harvest
Season
Juice Ascorbic
Acid (mg/100
g)
Juice
Lycopene
(mg/100 g)
Juice Total
Sugars
(mg/mL)
Juice Pectin
(per cent)
Conventional mid 33.6 0.52 94.2 0.09
Organic mid 41.5 0.25 95.6 0.09
Table 7.8:Acidity, Soluble Solids Concentration, and Consumer Intensity and
Acceptance of Conventional vs Organic Rio Red Grapefruit
Production
System
Harvest
Season
Juice
Titratable
Acidity
(per cent
citric acid)
Juice
pH
Juice
Soluble
Solids
Concent-
ration
(per cent)
Juice Consumer
Intensity and
Acceptance
Ta r t Sweet Overall
Conventional mid 1.07 3.3 10.3 4.2 5.0 6.5
Organic mid 1.24 3.2 10.8 a 5.6 3.8 5.9
The consumer intensity (tartness and sweetness) or acceptance (overall) rating based on
a scale of 1-10 for tart and for sweet: 0-4.0, not tart or not sweet; 7.1-10, extremely tart or
extremely sweet; for overall: 0-4.0, extremely dislike; 7.1-10, extremely like (n=75
Table 7.9: Phenols: Flavonoid (Naringin), Furanocoumarins (Bergamottin,
DHB, and DHB Dimers 708 and 728), Bergaptol, and Nitrate (NO3-N)
in Conventional vs Organic Rio Red Grapefruit
Production
System
Juice (µg/g)
Narin-
gina
Berga-
mottin
6’,7’-di-
hydroxy-
berga-
mottin
6’,7’-di-
hydroxy-
berg
Amottin
Dimer
708
6’,7’-di-
hydroxy-
berg
Amottin
Dimer
728
Berga-
ptol
Juice
Nitrate
(ppm)
Conventional 118.2 11.97 15.97 0.43 1.87 2.36 348
Organic 155.3 6.46 7.25 0.18 0.36 3.46 310
Sweet Orange
Ascorbic acid levels in oranges were higher in organic orchards than
in conventional orchards, especially, in Valencia late (82.0 mg/100 ml for
conventional vs. 86.0 mg/100 ml for organic system) and Baia oranges (34.9
mg/100 ml for conventional vs. 57.4 mg/100 ml for organic system). However,
Organic Culture of Tropical and Subtropical Fruit Plants
140 |
the differences in ascorbic acid content for the remaining four cultivars in these
two systems of production were not recorded (Duarte et al., 2010).
In “Valencia late,” the concentration of tartaric acid was higher in
conventionally grown fruits. Comparing the two modes of production in all
cultivars, it was found that the fruits of organic farming had more tartaric acid
(32.0 mg/100 ml) than those of conventional agriculture (28.2 mg/100 ml)
(Duarte et al., 2010).
In organic farming, malonic acid concentration was higher in six cultivars,
i.e., mandarin (cvs. “Carvalhais”, “Fremon”, “Fortune”, “Hernandina” and
“Fina”) and lemon (cv. “Lisbon”)and lower in mandarin cv. “Wilking” and sweet
orange cv. “Dalmau” (Duarte et al., 2010). The content of citric acid, ascorbic
acid, malic acid, tartaric acid, and malonic acid in mandarins, sweet oranges, and
lemons was generally higher in organic citrus fruits than in conventional ones
(Duarte et al., 2010). However, with respect to oxalic acid, the organic fruit had
a lower concentration in comparison with conventional farming for mandarins,
sweet oranges and lemon (Duarte et al., 2010). This is also not true to all the
cultivars; for instance, oxalic acid was higher in the fruits from organic orchards
(14.9 mg/100 mL) than in those from conventional orchards (10.0 mg/100 mL)
in “Fremont” mandarins (Duarte et al., 2010). The quality attributes of citrus
fruits may not always be associated with the system of production but depend
strongly on citrus species and cultivars. Sweet orange fruits from organically
grown orchards showed higher acidity, ascorbic acid, and total sugar content
as compared to conventional systems (Table 7.10).
Table 7.10: Physico-chemical Analysis of Conventional and Organically
Grown Sweet Orange (Citrus sinensis L. Osbeck)
Cultivation
Systems
Acidity
(per cent)
Total sugars
(g per cent)
Density
(g/cm3)
Brix
(o)
Ascorbic Acid
(mg per cent)
Organic 0.66±0.03 14.18±0.69 1.03±0.01 9.97±1.06 39.13±1.47
Conventional 0.45±0.01 9.67±00 1.03±0.02 10.23±0.52 35.49±1.52
Source: de Castro et al. (2014).
3. Propagation
The agro-ecological conditions of the north-eastern hill region of India are
very suitable for the cultivation of citrus; however, the productivity of citrus
crops is quite low as compared to national productivity. The availability of
virgin nursery sites is critical to organic production. It lowers the risk of soil-
borne diseases such as Phytophthora and Pythium, in addition to pests such
as nematodes, to which citrus seedlings are very susceptible. As a result, the
adoption of appropriate technology in the management of citrus nurseries will
increase the region’s citrus productivity. All seeds and plant material used
must be organically certied.When certied organic seed and plant materials
Organic Cultivation of Citrus (Citrus spp.) | 141
are unavailable, conventional seed and plant materials that have not been
chemically treated must be utilized. It is prohibited to use genetically engineered
seeds, transgenic plants, or plant material. The planting material for citrus can
be multiplied by both seed and vegetative means.
3.1. Seed Propagation
The most common traditional method of production of planting material
in citrus, including mandarin, sweet orange, etc., is through seed, because seed
is polyembryonic and produces more than one seedling. It is a commercial
propagation technique for acid lime. The selection of nucellus and healthy
seedlings, which in turn give true-to-type plants, is the most important aspect
of citrus cultivation because growth and production depend upon the quality
of seedlings. Seeds should be collected from productive mother plants that are
healthy, high-yielding, and disease- and pest-free.
Primary nursery: Primary nurseries are raised either in seed beds of 1-1.5
m width or 10-15 cm height of convenient length. It can also be sown in plastic
trays (size: 60 x 40 x 12 cm) with a hole at the bottom of the tray to drain excess
water. The tray is lled with solar-sterilised media and kept 1.5 feet above
the ground on a cemented oor in a net house or green house to check for
contamination. The mucilaginous covering on the seed must be removed after
extraction by washing and rubbing in water or rubbing in wood ash, and the
seed is then dried under shade. Following this, the seed treatments can be done
with Trichoderma viride and Pseudomonas uorescens at a rate of 5–10 g per kg of
seed. When there is a high prevalence of seed-borne disease, the seeds can be
treated with clove and cinnamon oil or any other seed treatment solution. Seeds
should be sown in the nursery immediately after extraction (within 1 week) at
a depth of 1.5–2.0 cm at a 10 x 5 cm distance (in the seed bed) and 2.5–3.0 cm in
the rows (in the tray). After sowing, light irrigation is given with a water can.
Before sowing, the media mixture is solar sterilised for at least two days in full
sun by covering it with a polythene sheet or by burning dead plant material
over the site. Soil drenching with suspensions of T.viride and P. uorescens (@
10 g each in 1 litre of water) in cases of heavy soil infestations. About 1-2 days
after media treatment, it can be used in plastic trays and polybags. In extreme
cases, the mixture can also be steam sterilized.
Secondary nursery: Seedlings are transplanted in secondary beds or
polythene bags of 8x4’’ with 2-4 holes at the bottom (containing equal parts
of soil, sand, and FYM) or root trainers (1 part soil + 1 part sand + 1 part coco
peat + 2 part compost) at 4-6 leaf stages. The media mixture must be solar
sterilized. Avoid planting too small or too tall seedlings when transplanting to
ensure uniform nucellar seedlings. Taproot seedlings with hook-necked, bent,
or distorted taproots should also be avoided. Prior to transplanting, seedling
treatment must be carried out by dipping the roots in fresh water and then in
a suspension containing T.viride (10 g in 1.0 litre of water) + P. uorescens (10 g
Organic Culture of Tropical and Subtropical Fruit Plants
142 |
in 1.0 litre of water). Allow the seedlings suspended in this solution to soak for
15–20 minutes before transplanting. Seedlings raised inside the polyhouse house
have straight growth with a single stem, healthy, least infested with insect pests,
and are ready for planting within one year. While the seedlings raised in open
conditions take more than 1½ years to profusely grow. After 12–18 months of
growth, seedlings are ready for planting in the main eld or for grafting and
budding. Seedlings for planting should be strong, healthy, free from pests and
diseases, with uniform growth, and about 60–90 cm in height.
Selection of Elite Mother Plants
Disease resistance, drought resistance, high quality, and yield performance
should all be considered while choosing cultivars for scion production.
“Valencia” is a famous cultivar of sweet orange for juice purposes, and it is
known to perform well under organic cultivation. “Washington Navel” is mostly
used as a fresh fruit. Other African cultivars include “Hamlin,” “Tangelo,”
“King Star Ruby,” “Red Blush,” and several other varieties that are suitable for
organic production. The progeny plants used as a source of bud wood should
have a well-known pedigree, high fruit productivity and quality, and be disease-
free. The bud wood from such plants must be virus-free and certied. Planting
materials should be from reputable nurseries to ensure that they are free of
diseases (particularly viruses) and pests and that the authenticity of rootstock
and scion cultivars is guaranteed.
Selection of Rootstocks
Although the majority of citrus orchards in India are made up of grafted
trees that combine the best qualities of the scion and the rootstock, however, in
the north-eastern hill region of India, the majority of the orchards are of seedling
origin. The selection of rootstock should be based on its adaptability to local
conditions and resistance to soil-borne diseases. The most extensively planted
rootstock is sour orange (Citrus aurantium L.), which is an excellent rootstock
for areas free of Citrus Tristeza Virus (CTV). Rough lemon (Citrus jambhiri) is
another common rootstock, but it should be avoided in locations where blight
and nematodes are prevalent.
3.2. Vegetative Propagation
Budding technique: Budding of Khasi mandarin should preferably be
done in a season when bark of the rootstock seedlings slips, i.e., either in
February-March or in July-August, which varies with regions, using the “T”
or shield budding method. In Maharashtra, budding of Nagpur mandarin is
usually done in the months of November-January using T or shield budding
methods. In the case of Kinnow mandarin, the best time for T or shield budding
is February-March or August- September. In Khasi mandarin, a T-shaped cut
is made with a budding knife in the bark at 15-20 cm above ground level. The
two aps of bark are loosened with the help of bare blade of a budding knife. A
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shield-shaped patch of bark measuring 2.5 cm in length is removed, containing
a bud from the scion of the selected mother plant. The bud is inserted into
the ‘T’ cut on the stock. The budded portion is wrapped with 100-200-gauge
polythene strip, leaving the bud open. It is preferred to bud at a height of 9
inches above ground level to protect the buddings from foot rot infestation. Buds
should be collected from healthy, disease-free trees of the desired cultivar and
it is commonly selected from the next to last growth ush (the wood behind
the current ush) and from the current growth ush after it has matured and
hardened. Bud wood should be well developed but still dormant, round (not
angular as in young wood), relatively straight, and have well-formed buds in
the leaf axils. The scion (bud stick) material for bud wood should be selected
on the mother plant before one week of budding operation, and leaves should
be cut off, leaving a stub of the petiole, which helps in swelling buds. Trimmed
bud sticks should be labelled and used immediately or placed in plastic bags
in a cool place to avoid exposure to desiccation. Budding is the most common
method of vegetative propagation for sweet orange using rough lemon as
rootstock on acommercial scale in the region.
Soft wood/wedge grafting: Grafting is a specialized type of plant
propagation where part of one plant (the scion) is inserted into another (the
rootstock or stock) in such a way that they unite and grow as a single plant.
Budding success on Khasi mandarin under Meghalaya conditions is low
therefore, soft wood grafting developed by the ICAR Research Complex for NEH
Region, Umiam, may be used as an alternative method for raising the quality
planting material of Khasi mandarin. Soft wood grafting should be done in July-
August on 60–90 days old rootstock. Proper selection and preparation of scion
stick are very important for higher success. The previous season’s 3-4 months
old shoot is ideal for this technique. The scion shoots of 2-4 mm thickness with
3– 4 healthy buds of 8 – 10 cm (short internodal length) long and round shape
is used for grafting. Selected scion shoots are defoliated on mother plant, about
7-10 days prior to detaching. At the same time, the leaves of selected scion should
be cut off, leaving a stub of the petiole, which helps in forcing the dormant buds
to swell. After selection of thescion, therootstock (seedling) is headed back by
7.5–10 cm long stem above the polythene bag, and leaves of rootstock should
also be removed, leaving 2-3 leaves on lower side of rootstock before grafting.
Then, the beheaded rootstock is split about 1.5-2 cm deep through the center of
stem with a grafting knife. A wedge-shaped cut, slanting from both the sides
(1.5-2 cm long) is made on the lower side of the scion shoot. The scion sticks
then inserted into the split of the stock and pressed properly so that cambium
tissues of rootstock and scion stick should come in contact with each other. The
union is then tied with the help of a150-gauge polythene strip, 1.5 cm wide and
20-25 cm length. Immediately after grafting, the graft is covered by a 2x15 cm
long white polythene cap. The scion starts sprouting after20 – 25 days, which
is visible from outside. The cap is removed after 35 days in the evening hours,
or grafts should be kept inside the polyhouse to ensure more grafting success,
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early sprouting, and better growth as compared to open and inside the net
house conditions.
Cutting: Assam lemon is commercially propagated by cutting. A cutting
of 10-15 cm long and 2.5 cm thick is taken from the middle portion of a one-
year-old shoot. Top cut is made about 1 cm above the node and the basal cut
slightly below a node. Cuttings were planted in June-July. The cuttings are
treated with IBA (500mg/L water) solution or basal end dipped with rootex
powder for better results.
Air layering: Sweet orange, sweet lime and Khasi mandarin are propagated
through air layering by the farmers of the North-Eastern region. Air layering
is done either in spring or in monsoon season and a 1-2 years old shoots are
selected for layering. Leaves are removed from the base of the selected shoots
and stem girdled by removing of bark about 2-3 cm wide at the place where
leaves were removed. IBA @ 500-1000mg/L water or a combination of IBA
+ NAA @ 500mg/L water is applied on the girdled area. The girdled area is
covered with handful of moist soil and sphagnum moss and wrapped with
polythene strip. Rooted layer is cut just below the girdled portion and planted
in polythene bag or nursery beds in shady place.
3.3. Tissue Culture Technique
The procedure for large-scale citrus plant multiplication via nucellar
embryogenesis has been standardized. To maintain cultivar purity, weak, and
off-type seedlings are rouged out. Damping-off can be minimized by providing
good drainage such as raised beds, efcient irrigation system, etc. Application
of suspensions of T.viride and P. uorescens (@ 10 g each in 1 litre of water) or
Jivamrit (mixed with water) around the rootzone to control damping-off disease.
A plant extracts of Eupatorium cannabinum is also known to completely inhibit
the growth of the fungus (Plantix, 2023). Spray of Nimbicidine or Neemazal
@3ml/L at 15 days interval are found to prevent pest and disease infestations.
Weeding and light hoeing are applied to prevent weed infestation and to make
the soil porous. Foliar applications of vermiwash (5 per cent), Panchagavya (3
per cent), and farm-made protein hydrolysate (4-5 ml/L of water) are all ideal
constituents for better growth of seedling plants. Depending on the situation,
either one, a combination of two, or all of these can be used. The side shoots
of seedlings should be removed regularly to maintain a single straight stem,
and sprouts below the bud/graft union should also be removed periodically.
Frequent and light irrigation should be given to maintain sufcient moisture.
Care should be taken to avoid water stagnation in the bags.
4. Variety and Rootstock
The most commercial important species of citrus fruits are sweet oranges
(Citrus sinensis), limes (C. aurantifolia), grapefruits (C. paradisi), lemons (C. limon)
and mandarins (C. reticulata), often called tangerines (FiBL, 2011).
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Mandarins
The fruits of mandarins are easy to peeland are becoming increasingly
popular in the fresh fruit market. Mandarins are a huge, distinct, and diverse
category of citrus fruits that contain some of the best and most well-known citrus
fruits. These fruits are usually referred to as “loose-skin oranges”. The most
important mandarins in India are Nagpur mandarin, Kinnow mandarin, Coorg
mandarin, Khasi mandarin, and Sikkim mandarin. In the Mediterranean basin,
Clementines are the most commercially important mandarin fruit and Satsumas
in Japan. “Fortune”, “Kinnow”, and “Minneola” are examples of commercial
mandarins that are intraspecic or interspecic hybrids. “Ponkan”, “Ellendale”,
“Ortanique”, “Murcott”, and “Nadorcott” are examples of chance seedlings.
Sweet Orange (Citrus sinensis (L.) Osbeck)
Sweet orange is the main group, which is used both for fresh fruit and
processing. It probably originated in China, but its major centre of diversication
is the Mediterranean basin. The major varieties in this group are classied as
follows:
P Navel oranges (Washington Navel, Navelina, Navelate, Powell, Rhode
Navel, Cara Cara).
P Blonde oranges (Shamouti, Valencia Late, Hamlin, Pineapple, Trovita,
Salustiana, Delta Valencia, Pera)
P Pigmented or blood oranges (Tarocco, Moro, Sanguinelli, Maltese)
P Sugar or acid less oranges (Meski Maltaise and Shamouti Maski or
Shamouti Moghrabi)
P Other sweet oranges (Jaffa or Florida Jaffa, Joppa, Foster, Marrs or
Marrs Early, Parson or Parson Brown)
P Mosambi and Sathgudi are always classied as sweet oranges in India
due to their low acid level. ‘Sohnairiang’, the locally popular cultivar
of sweet orange in the north-east India.
Lemon
Several lemon cultivars having major contribution in the world production
include Lisbon, Verna, Eureka, Feminello, Fino and Primoori. While, Assam
lemon, Italian lemon, Pant lemon, Galgal and Eureka lemon, Sevilla and Malta
lemon varieties are popular in India.
Lime
Two main types of limes are distinguished: the small diploid and seedy lime
(Mexican) and the big seedless triploid lime (Tahiti, Bears). The other cultivars
of acid lime are Vikram, PKM, Prumalini and Rashraj or Sharbati.
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146 |
Rootstocks
It is advised to grow citrus using vegetatively propagated planting
materials, with the exception of acid lime. The composite plants are required
to regulate the crop maturity season in order to ensure faster, higher yield and
quality, uniform fruiting, and adaptation to diverse agro-climatic circumstances.
However, not all rootstocks are universally suited for one reason or another.
The root stock that was supposed to be suitable for certain species or conditions
may fail completely in another. Furthermore, there is no guarantee that the best
rootstock available today will not fail in the future. As a result, research must
be carried out continuously.
The following are the qualities of ideal root stock
P The rootstock must be compatible with the scion variety and provide
the tree the longest economic life possible.
P It should be adapted to the agro-climatic conditions of the desired
location.
P It should be resistant to the pathogens (primarily soil-borne) and pests
that are prevalent in the area.
P It must have a positive impact on the performance, bearing, and quality
of the scion’s fruits.
P Other desirable characteristics of the stock include salt tolerance,
drought resilience, frost endurance etc.
P It is also critical that the stock exhibits strong nursery characteristics
such as good germination, a high degree of polyembryony, the capacity
to acquire graftable size in a short amount of time, and the avoidance
of excessive branching.
Rootstock Recommended for different Citrus Species
The most widely used rootstock in the country is Rough Lemon (Citrus
jambhiri Lush) for most of the citrus scions, followed by Kharna Khatta (Citrus
karna) which is more popular in Punjab and Uttar Pradesh. These have become
more or less well established. For mandarins, Karna Khatta, Nasnaran, and
Rough lemon, and for grape fruit, Kharna Khatta are usually employed as
rootstocks in Punjab. But sweet lime is recommended for Mosambi under wet
subtropical conditions with a high temperature. In western India, Jambheri is
employed as a rootstock for Mosambi. Rangpur lime (Citrus limonia) proved to
be the best for Nagpur mandarins due to its resistance to gummosis and root
rot. In Assam, Rough lemon has been found to be the most promising rootstock
commercially for Khasi mandarins, Valencia, Mosambi, and Malta, lime, lemon,
etc., and pummelo for grapefruit. Sathgudi rootstock for Sathgudi and Batavian
oranges in Telangana have given better results than others. While Gajanimma
proved superior for acid limes and lemons. Under Coorg (Mysore) conditions,
Organic Cultivation of Citrus (Citrus spp.) | 147
both Rangpur lime and Kodakithuli orange (Citrus reticulata Blanco) have shown
great promise as rootstocks of Coorg mandarin. The rootstock Gajanimma is
recommended for Nepali oblong lemon.
5. Orchard Establishment
5.1. Site Selection for Orchards
Citrus trees can be grown in a wide range of climatic and soil conditions.
But proper site selection remains the key to successful organic production.
Soil
Citrus cultivation can be done on the plains as well as in hilly areas with
good drainage and fertile soil. The soils of citrus-growing regions in the north-
eastIndia are all acidic, which hampered the availability of important nutrients
to the plants and reduced yield. The existing orchards’ topography in the north-
east region of India ranged from moderate to steepslopes, resulting in heavy
loss of fertile upper topsoil and leaching of nutrients every year due toheavy
rains, causing nutritional deciencies. It is also observed that the soil condition
of mandarin orchards in the Dawki area of Meghalaya is very stony, and such
types of soil restrict root growth activity as well as the availability of nutrients
and moisture (Rymbai et al., 2022). Therefore, the soil of the site should be
deep (at least 1 m), loose, and have good drainage, as tree growth is reduced
in poorly drained soils or where compacted soil layers are present in the root
zone. Furthermore, poor drainage causes problems with Phytophthora and other
soil-borne diseases. Steep slopes and shallow, gravely, and heavy soils should
be avoided for orange cultivation. Soil having a pH of 5.5 to 6.5 is considered
most favourable for the cultivation of citrus crops.
Agro-climatic Conditions
Mandarin thrives well in sub-tropical to semi-temperate climates up to 1000
m above sea level, having high humidity and requiring warm summers and
mild winters for its successful growth. While Assam lemon is quite suited at low
to mid-altitudes. Climate has a signicant effect on nearly all aspects of citrus
growth and quality development. Ideal temperatures range from 13 oC to 38 oC.
Citrus plants suffer from the extreme heat.At higher temperatures, owers and
leaves drop prematurely. Light and frequent rainfall or irrigation throughout
most of the year is necessary for citrus, however, dry and hot temperatures
during the day and cool temperatures at night are favourable conditions for good
colour development. The site selected for the orchard should have sufcient
sunlight. In order to get sufcient sunlight in hilly regions, planting should be
done in southward directions.
5.2. Conversion Period
The interim period required for the establishment of an organic management
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system and the improvement of soil fertility is known as the conversion time.
While the conversion phase may not always be long enough to improve soil
fertility and restore ecological balance, it is the initial phase when all of the
efforts are needed to achieve the goals of an organic management system. A
conversion of a farm must be followed according to a clear plan. The producer
must update this strategy to include all requirements to be met under these
standards during the conversion phase. All of these conditions will apply from
the start of the conversion period until it concludes. The conversion time may
begin on the date the operator is rst inspected by the Certication Body. A
full conversion period is not necessary if de facto requirements dened by these
standards have been met for several years and can be validated using available
documentation. Inspection must be undertaken at appropriate intervals prior
to the rst harvest in such instances.
5.3. Duration of Conversion Period
In case of citrus, being a perennial plant, the rst harvest may be certied
as organic after at least 36 months of organic management according to the
requirements prescribed under these Standards. The accredited Certication
Bodies shall decide in certain cases, for extension or reduction of conversion
period depending on the past status/use of the land and environmental
condition. Twelve months reduction in conversion period could be
considered,on condition, documentary proof has been available with the
accredited Certication Body that the requirements prescribed under these
Standards have been met for a period of minimum three (3) years or more. This
could include the land that been certied for minimum three (3) years under the
‘Participatory Guarantee System’ implemented by the Ministry of Agriculture
and wherein, the products approved for use in organic farming have been
applied. The accredited Certication Bodies shall also consider such a reduction
in conversion period, if it has satisfactory proof to demonstrate that for three
(3) years or more, the land has been idle and/or it has been treated with the
products approved for use in organic. Organic fruits in conversion shall be sold
as “produce of organic fruits in conversion” or of a similar description, when
the requirements prescribed under these Standards have been met for at least
twelve months (APEDA, 2023a).
All necessary precautions must be taken to reduce contamination from
both outside and within the citrus orchard. To prevent contamination from
conventional orchard management, buffer zones must be maintained. The buffer
Zone should be large enough to prevent inadvertent contact with prohibited
compounds applied to adjoining conventional land areas/orchards.
5.4. Planting
Layout and System of Planting
Under an organic management system, the primary requirement is a
Organic Cultivation of Citrus (Citrus spp.) | 149
planting density that allows for optimal light penetration and aeration while
also providing adequate sunlit space for intercrops, green manures, and cover
crops. Organic cultural practices are easier in low-density planting systems
due to the availability of sufcient space for cover crops and other cultural
operations such as the application of compost, the management of pests and
diseases, and the use of mechanical devices for mowing and cutting cover crops.
In plain areas, orchards can be established in a square system at a spacing of 5 x
5 m (for mandarins and oranges) and 3 x 3 m (for lemons, limes). Whereas, on
hill slopes, contour bunds can be made at a distance of 5–6 m depending upon
the gradient, and then half-moon terraces can be made in between two contour
bunds with the required spacing (Rymbai et al., 2022).
After cleaning the vegetation, pits are dug to the following sizes: 0.75 x
0.75 x 0.75 m (for mandarin and oranges) and 0.45 x 0.45 x 0.45 m (for lemons).
To aid speedy establishment of the plants, the pits are relled with 30 cm of
uppermost soil along with 20 kg FYM, 300 g rock phosphate, and 50 g neem
cake. The pits are lled about 10–15 cm above ground level.
Planting Time
The best time for planting of citrus plant is after the onset of monsoon, June
to August. Seedlings and grafted plants of mandarin (Khasi mandarin, Coorg
mandarin, and Darjeeling mandarin), acid lime, sweet orange, lemons, and
other citrus can be dipped in a suspension containing T.viride (10 g in 1.0 litre
of water) and P. uorescens (10 g in 1.0 litre of water) for about 15-20 minutes
before transplanting directly in the eld. In addition, incorporate into the pit soil
50 g each of T.viride and P. uorescens in 10 kg of FYM before planting (Shree,
2020).If there is no rain after planting, light irrigation should be given. The bud/
graft union should be kept at least 15 cm above the ground level.
A vigorous leguminous crop like velvet bean (Mucuna spp.), sunnhemp
(Crotalaria spp.), or lablab (Lablab purpureus) may be sown prior to planting,
which are then slashed and mulched shortly before planting the citrus trees.
Then the soil will be enriched with organic matter and nitrogen, both stimulating
soil microbial activity.
The citrus seedlings should be planted carefully. The budding point of grafts
must remain above the soil to avoid exposing the scion to root rot diseases and
to make sure it does not start rooting itself. Depending on the planting season,
supplementary watering or irrigation may be required to support the growth
of the young seedlings. Shoots that grow below the budding union must be
removed. These shoots, if not removed, will retard growth or kill the scion part
of the budded shoot.
6. Nutrient Management
There are some specic technical aspects of organic citrus cultivation that
distinguishes it from conventional citrus farming. The organic standards limited
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150 |
the use of inputs and management practices to certify organic orchards. Organic
fertilizers are more expensive and are absorbed more slowly by the roots than
commercial fertilizers. In order to minimize the orchard’s reliance on material
inputs and management interventions as part of the certication process, the
focus of certied organic orchard management should be on eliminating chemical
inputs, improving soil health, and nding ways to increase the plant’s innate
resistance to diseases, pests, and weeds. As a result, in contrast to conventional
citrus orchards in Spain and Italy, organically managed soils were found to
have higher amounts of organic matter, humic substances, carbohydrates,
aggregate stability, microbial gums, microbial biomass, and enzymatic activity
(Albiach et al., 1999; Canali, 2003). For instance, mulch conserves soil moisture
and moderates the soil from temperature extremes. It also enriches the soil
with benecial organic matter on its decomposition (Abouziena et al., 2008). In
nutrient management, the effective plant requirements should be considered
in,terms of an input/output balance (Watson et al., 2002b). The balanced
nutrition of citrus plants should be a top management priority for citrus growers.
Regular monitoring of the nutritional level of plants and the soil content is
necessary for a long-term sustainability of the organic orchard. Citrus uptake
may reect the quantity of nutrients lost in harvested fruit, abscised fruitlets
and owers, senescent leaves, pruning wood, and root turnover. In immature
trees, however, there is a signicant requirement for tree growth (Mattos et al.,
2006; Menino et al., 2007). Since external nutrient intake is minimal during the
spring season, the spring ush depends on a vigorous remobilization of stored
nutrients (Menino et al., 2007).Similarly, before leaf fall occurs in citrus trees,
a substantial amount of the nitrogen and other nutritional elements in older
leaves are reallocated within the citrus plants. A part of these nutrients become
locked up in the permanent structure of the tree (trunk, major branches and
roots) and are unavailable for plants. The majority of biologically xed nitrogen
comes from cover crops and green manures. The contribution amount of cover
crop can be computed by calculating the biomass output per square metre. The
previous reports suggested that the total organic carbon (TOC) was higher in
organically managed soils (13322 mg/kg) with respect to conventional citrus
orchards (10776 mg/kg) (Canali et al., 2002). Carbon mineralization has been
identied as a reliable property for assessing soil microbial activity, with the
ability to provide information on soil metabolic status and organic matter
turnover (Trinchera et al., 2001). Organic soils had signicantly higher carbon
mineralization (894 mg/kg) than conventional soils (575 mg/kg). The NH4+-N
was also higher in organic (8.0 mg/kg soil) than in conventional orchards (7.19
mg/kg soil) (Canali et al., 2002).
Khasi Mandarin and other citrus fruits are considered highly nutrient-
responsive crops. Cover cropping, green manuring, mulching, and nutrient-
rich manure treatments are the main sources of nutrition for citrus plants. It is
advised that FYM (@ 15–25 kg/tree) and/or vermicompost (@ 4.5–9 kg/tree)
may be applied to young plantations (1–7 years of age). A tree ages of 7 years
Organic Cultivation of Citrus (Citrus spp.) | 151
onwards, FYM (25–50 kg per tree) and/or vermicompost (15–30 kg per tree) may
be applied annually in two equal splits either solely or in the mixture to obtain a
sustainable yield (Avasthe et al., 2014). After manuring, trees need to be lightly
irrigated. In addition to compost manures, in July and August, while the plant is
actively growing, about 2 t/ha of neem cake should be applied. Complex organic
resources including animal and plant residues, algal extracts, food industry
byproducts, etc. may also be used to supplement the nutritional requirements.
A fast-growing green manure crops are trimmed and ground in the eld can
provide signicant amounts of humus and nutrients. Besides, in an organic
system, the pruned parts of a trees should be chopped and incorporated into
the soil enhances soil quality, reduces the requirement for chemical fertilizers
inputs, and helps cut down on CO2 emissions (Beltran-Esteve et al., 2012). Rock
phosphate should also be added to supplement phosphorous. In acidic soil, soil
application of agricultural lime (@ 500 g per plant or dolomite (@ 100-200 g per
plant) in alternate years is needed to correct the pH level. Normally, young
plants are manured (FYM or compost) through soil application once a year. FYM
or compost is typically applied once under rainfed conditions or twice under
irrigated conditions and concentrated manure mixtures are applied twice or
three times. In the north-east of India, manure is applied at the tree basin twice
a year, i.e., in June-July and after harvesting in December-February, or 2-4 weeks
prior to owering, to encourage good fruit formation and development. Cow
urine can be used to enrich well-decomposed FYM or compost. The manures
are placed in a drip circle beneath the canopy in a 20–25 cm-deep trench dug
within the foliage periphery but about 1 meter away from the main stem in
the adult plants. The manures are then mixed thoroughly by lightly hoeing.
After application, cover the trench rst with soil and then with dry or wet
biomass as mulch. Drench the mulched ring with Jivamrit mixed with water.
Plant feeding via foliage is an essential approach in organic farming. A foliar
spray of micronutrients (water soluble organic sources) during the ushing
period is essential for healthy growth, fruiting, and quality. Vermiwash (5 per
cent), Panchagavya (3 per cent), and farm-made protein hydrolysate (4-5 ml/
lit of water) are all ideal constituents. Depending on the situation, either one, a
combination of two, or all of these can be used.
7. Orchard Floor Management
Consideration for orchard oor management should be made before
establishing an orchard. Once the orchard is established, organic management
practices for orchard-oor care must be followed on a regular schedule. The
ideal orchard oor would be easy to maintain, encourage tree and fruit growth,
sustain the orchard’s soil structure, minimize erosion potential, and not compete
with the trees for water or nutrients, nor host insects or other pests. Therefore,
the primary objective of orchard oor management in most organic systems
is to promote sustained soil fertility and orchard productivity. In practice, no
single orchard-oor management system can fulll all of these goals; rather, a
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152 |
balance of the above criteria must be met while also considering soil type, slope,
tree age, irrigation, and harvesting methods.
7.1. Cover Crops
The ability to maintain permanent soil cover is vital to organic citrus
orchard management success. The adoption of soil cover reduces soil erosion,
improves soil structure, xes nitrogen, suppresses weeds, and provides habitat
for benecial insects. Cover crops, on the other hand, may harbor some pests
and diseases, resulting in more pest damage. There are numerous reasons to
cultivate cover crops in citrus orchards, but there are also instances where a
certain variety/type of cover crop may be detrimental to the economic crop
output. Therefore, species of crop cover and their eld management is important
and should be carefully chosen to prevent unintended issues with rodents,
diseases, or nematode hosts. The location of the orchard, irrigation system,
pest management issues, and nutrient requirements all inuence the choice of
a cover crop. The orchards are relatively easy to provide adequate nutrition
with leguminous cover crops and organic manures. However, for orchards with
grass cover crops, greater nitrogen supplementation is required through the
application of organic manure, including compost, bone meal, feather meal, etc.
Flowering plants such as Alfalfa (Medicago sativa), African blue basil (Ocinum
basilicum), Centrosema pubescens, Desmodium, Cassina obtusifolia, Alysicarpus
vaginalis can also be grown as cover crops. In addition, citrus trees are often
grown in agro-forestry systems with other fruit trees, such as mango, jackfruit,
banana, palm, coffee, and cocoa, as well as with leguminous trees (like Albizia) or
other kinds of evergreen trees. Citrus is sensitive to strong winds, so it benets
from the trees’ function as windbreaks in windy places.
7.2 Mulching
Organic mulches can effectively manage weeds, retain moisture, and
provide additional nutrients. Unfortunately, most of the organic mulches
available today for weed control are feasible only for small operations. According
to the study, mulch thickness should be 3-4 inches to successfully suppress
weeds; one inch of mulch actually increases weed growth (Vossen and Ingals,
2002.). If done by hand, this type of mulching required a signicant amount
of material and a signicant cost in application. On bigger scale operations,
modied side-discharge animal feed carts may be deployed. Organic mulches
are frequently a shelter for rodents, which can cause tree trunk damage. Fabric
mulches are another method for weed control in-row. Such mulches eliminate
any weeds, enable quick penetration of water from sprinklers or emitters above,
and provide a clean surface to prevent disease inoculation. Although the initial
prices are signicant, however, these materials durability is ten years, making the
investment equivalent to conventional herbicide costs (Vossen and Ingals, 2002).
Organic Cultivation of Citrus (Citrus spp.) | 153
7.3 Weeding
Weed is a major issue in organic citrus cultivation, increases production
costs, insect-pests, and disease incidence. Weeds growing around tree trunks
may also create a favourable environment for pathogens that infect the trunk
and roots (Futch and Singh, 2010). Very heavy rainfall occurs during the period
of May–October, favouring the growth of weeds in the orchards. Weeds can
never be completely eradicated under an organic system; however, they can
only be managed periodically. Therefore, it is essential to identify a critical
period of weed management (CPWM). CPWM is a period in the life cycle of the
crop when weeds must be kept out in order to maintain yield. In addition, the
tree basin must be kept clean as far as possible. If weeds have been managed
throughout the critical phase, the later-emerging weeds won’t impair yield. In
citrus, the critical periods for weed management may be identied as April–May
and August–September.
The general practises for weed reduction are frequent hoeing, hand
weeding, and light tillage. Such operations will improve soil aeration and health;
they must be carried out with care to avoid damaging the roots. Mulching is
essential in managing the weed menace. Schiawallichi (Chilaune) is the most
commonly used leaf mulching material in north-east India, followed by Artemisia
vulgaris (Titepati), which also reduced disease problems (Avasthe et al., 2014). A
permanent soil cover is an essential part of the organic orchard production
system. The locally available leguminous crops, such as lablab (Lablab purpureus),
sunnhemp, and velvet beans, quickly restored deteriorated soils and effectively
suppress weed growth, x nitrogen, and prevent erosion. The cover crop should
be periodically trimmed to prevent strong competition between the citrus trees
and the cover crop. The growing of such cover crops suppressed the noxious
perennial grasses including Couch grass (Cynodon dactylon), Spear grass (Imperata
cylindrica), Panicum spp., Paspalum spp., Amaranthus spp., and others are
inhibited. Injuries to tree trunks and roots must be avoided if tools or equipment
are used since they could act as entry sites for soil-borne pathogens. In new
citrus orchard plantations, the soil conditions are effectively improved under
mulching. Organic growers face additional challenges in managing the orchard
oor, particularly weed management because most organic herbicides have
not performed well. However, “pelargonic acid,” a post-emergent and contact
chemical available under the brand name “Scythe,” has been demonstrated to
be successful as an alternativeto conventional herbicides. Weed growth can be
reduced by spraying “Scythe” with water at a rate of 3-5 per cent (Johnson and
Davis, 2014).
7.4. Orchard Bio-diversification
Increasing biodiversity in the orchard is one of the most essential organic
management approaches. The presence of a high degree of diversity including
the appearance of a highly diverse bird and insect community reduces the risks
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of insect-pest infestation and improves ecological pest control. An organic citrus
orchard preserves biodiversity through ground cover, the most noteworthy
plants being alfalfa, which has a productive correlation with soil fertilization,
and wild grasses, which have a positive association with wildlife. Plant one or
two rows of nitrogen-xing trees/bushes and owering, and other compatible
plants around the orchard and along the road/pathways or hedgerows, which
provide habitat and support for populations of benecial insects and birds, and
also help to increase biodiversity. Growing owering plants along the orchard
border by arranging small plants towards the crop and taller plants towards
the border also helps in creating diversity and the survival of benecial insects
(Shree, 2022). A high level of plant biodiversity encourages a comparably
diversied population of microbial and insect species, which contribute to pest
management; but, when natural predators are insufcient to exert biological pest
control, treatments with mineral oil or parafn are appropriate (Beltran-Esteve et
al., 2012). Aside from cover crops, a variety of plants with pesticide value (such
as adhathoda, Ipomea, Calotropis, nirgundi, and others) and insectary plants
(such as mustard, sunower, alfalfa, marigold, French bean, cowpea, maize,
coriander, spearmint, peppermint, Ocimum, and others) can be interplanted and
used as green manure or mulch. Nitrogen xing plants like Gliricidia, Leucaena
leucocephala, perennial pigeon peas, etc. can also be planted on borders.
7.5. Intercropping
Khasi mandarin orchards of grafted/budded plants generally started
bearing by 3rd years after planting, however, commercial bearing started from
6th year onward. Intercropping can be done during the 1st – 5th years of orchard’s
age in the interspace of trees. Intercropping boosts crop productivity and
protability overall, enhances pest and disease control, checked weed growth
and maximizes the use of available nutrients, water, and light (Kremer, 2019).
The intercrop should be of short duration and shallow rooted to avoid resource
competition with citrus trees. Leguminous plants such as peas, French bean, rice
bean, black gram, cowpea, leafy vegetables, papaya, etc. may be incorporated
on a rotation basis. Medicinal/herbal plants such as Aloe vera can also be
intercropped in alleys and along the borders. Aloe vera is a shade-tolerant plant
that has been successfully interplanted with citrus and other fruit trees (Shree,
2022). Growing pineapple on the border of the terrace in the hilly region is very
benecial, besides providing additional income, it also prevents soil erosion and
reduced weed growth. However, care must be taken that the tree basin must
be kept free of intercrops, and exhaustive crops such as ginger, turmeric, etc.,
must be avoided due to their excessive nutrients and moisture consumption.
8. Irrigation Management
Irrigation is among the most expensive cultural practices in arid and
semi-arid regions due to prolonged dry seasons. In humid subtropical areas,
it is also a crucial cultural practice to sustain optimum fruit yield and quality,
Organic Cultivation of Citrus (Citrus spp.) | 155
which would otherwise suffer during brief dry spells. Citrus plants can
effectively conserve water and withstand extended droughts due to their wax-
coated leaves. However, in the rst year after planting, citrus plants required
protective irrigation, especially in the winter and summer. Citrus plants respond
favourably to irrigation in regard to growth, owering, and fruiting, while the
scarcity of moisture makes the plant appear unhealthy and the leaves become
pale and chlorotic. Studies have shown that efcient irrigation practices are
more benecial than other cultural practices, which result in higher yield and
quality (Levy and Boman, 2003).
Therefore, the identication of the critical stage of irrigation in citrus is
of great importance. During spring, adequate soil moisture levels are crucial
for proper fruit set and to support optimum fruit growth and development
through harvest (Kour and Bakshi, 2018). In regions with warmer winters and
insufcient cold induction, drought stress can accelerate oral bud induction
and be a benecial management tool. Similar conditions are also required for
the induction of out-of-season owering. In the late summer and fall, moderate
water decits are desirable to maintain high juice quality, particularly in juice
and early cultivars. In early mandarin cultivars, decit irrigation may decrease
fruit size and juice while increasing juice sugar. A typical tree requires 4 liters of
water per day in Florida for newly planted (rst-year) Mid sweet orange trees.
According to reports from Cuba, the summer water requirements of Valencia
orange trees are 2 mm of water per day for newly planted trees and 3 mm per
day for 4-year-old plants. In Florida, water use for 5 to 6-year-old “Valencia”
orange trees was highest (60 L/day) during May, i.e., just before the summer
rains began. The water use increased at a rate of roughly 20 per cent per year
from 4 to 6-year-old (Ennab and El-Sayed, 2014).
In early mandarin cultivars, decit irrigation may decrease fruit size and
juice, while increasing juice sugar. A typical tree requires 4 liters of water per
day in Florida for newly planted (rst-year) Midsweet orange trees. According
to reports from Cuba, the summer water requirements of Valencia orange
trees are 2 mm of water per day for newly planted trees and 3 mm per day for
4-year-old plants. In a Florida research, water use for 5 to 6-year-old “Valencia”
orange trees was highest (60 L/day) during May, i.e., just before the summer
rains began. Water use increased at a rate of roughly 20 per cent per year from
4 to 6-year-old.
The irrigation scheduling of a fully-grown orchard for optimum yield
depends on the stage of growth, citrus cultivars, prevailing climatic conditions,
daily course of evapotranspiration, soil moisture holding capacity, root
development, and target yields. It has been observed that the organic citrus
production approaches can more effectively utilize water resources than
conventional citrus farming. This is because the organic system has a higher
proportion of humus and organic matter in the soil, which aids in better moisture
retention, and thus helps in extending the interval of irrigation scheduling. The
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156 |
Mediterranean climate had heavy rainfall in the winter months but little or no
precipitation in the summer, hence, there is typically little or no requirement
for irrigation throughout the winter season, with the exception of drought
conditions.
In arid areas, salt leaching is a signicant factor for winter irrigation. It
should be noted that a 40 mm irrigation (400 m3/ha) is substantially more
effective than a 40 mm rainfall. This is because the irrigation-wetted area of the
orchard accounts for less than 25 per cent of the total orchard land area, and
the canopy, which acts as an umbrella, deects some of the rainfall away from
the irrigation-wetted area(Levy and Boman, 2003).
In summer rain climates, there may be a signicant quantity of rainfall
during the summer growing season. However, in these regions, the timing of
precipitation often results in periods not associated with the critical phase of
the plants and when rainfall is insufcient to meet crop water requirements,
necessitating the use of supplemental irrigation. Florida experiences its heaviest
rainfall from June to September, with little falling during the crucial months
of January to June. In addition to the annual rainfall received (1100 mm), the
supplement irrigation of 280 mm of water increased the yield of Valencia oranges
(8-9 years old) by about 22 per cent.
In the north-east of India, about 90 per cent of the rainfall occurs during
May–October, but there is less rainfall during the critical stages of owering
and fruit set in the months of January–May. In Khasi Mandarin, irrigations are
to be provided during dry spells at intervals of 15–20 days during November–
March to promote good owering during February as well as good fruit sets
and ushes in March–April. Proper soil moisture must be maintained during
late spring (after fruit set in April) and in hot weather during May to avoid the
stress that leads to a high “June drop” of young fruitlets. Likewise, optimal
soil moisture should be maintained to avoid the “pre-harvest drop” of mature
fruits, which can reduce prot. Regular, moderate irrigation increases owering,
fruit set, fruit size, and juice content, while reducing physiological fruit loss.
A high frequency of light irrigation is advantageous. Good water quality is
required with no heavy metals, harmful bacteria, and salt content. For organic
certication, regular water analysis is required.
Localized irrigation is the most practical watering method, it makes
mechanization more challenging. A jerrycan or plastic water bottle placed
adjacent to the stem of each plant to deliver water is a low-cost irrigation
technique, especially, for newly planted citrus saplings. The bottom or lid of
the jerrycans or bottles is perforated so that water can drip continually into the
soil surrounding the plant. The jerrycan or bottle is replenished after the water
is nished. Regardless of the age of the plant, adequate water management is
required year-round to develop a robust tree and a dense, healthy root system.
Organic Cultivation of Citrus (Citrus spp.) | 157
9. Moisture Conservation
Moisture conservation techniques are very important in the organic
management system. From April to October, heavy and prolonged rainfall
causes signicant soil erosion, particularly in sloping areas, as well as nutrient
loss and creates an environment conducive to the appearance of numerous
insect-pests and diseases. The long dry season from December to March also
causes a moisture stress problem. Adopting appropriate conservation measures
such as contour bunds, bench terraces, and half-moon terraces may aid in
minimizing topsoil erosion and organic matter losses during the rainy season.
Mulching is one strategy that can help conserve water in the soil. Mulching
materials such as paddy straw, and dry grass may help to alleviate moisture
stress during the winter, reducing soil erosion and weed problems during the
rainy season. Similarly, constructing trenches on the top side of trees across
the slope not only reduces soil erosion but also aids in moisture conservation
throughout the winter season.
10. Training and Pruning
In the rst year, 4 to 6 main branches are allowed in all directions to form
the framework of the tree at about 100 cm from the ground, and other branches
are removed periodically. Routine removal of undesirable branches like water
sprouts emerging from seedling rootstock should be carried out once a month
during the rst year and, subsequently, once in two or three months. In citrus
growing areas of the NE region, the required low temperature is available to
induce owering. In these areas, owering on orange trees is noticed in the
month of February- March (Ambia Bahar) and fruits matured in November-
December take about 9 months from owering to maturity. The bearing tree
often needs little to no pruning with the exception of undesired development
like water shoots, crossed, dry, and diseased branches. Pruning should be done
once a year after the fruit harvest (December and January, before owering),
and the cut end portion should be smeared with Bordeaux paste.
Under high density orchards, the lower and inner branches are shadowed as
the trees grow. As a result, only the outer canopy bears quality fruits, while, the
core portions of the canopy have poor or no fruit set. Pruning annually allows
light and air to penetrate the canopy of citrus trees and reduces humidity around
the plants, which aids in pest and disease prevention. Under such a system, the
tree height should be kept to less than double the planting distance in the row.
In bearing citrus trees, three major types of pruning include; i) Heading back
(to control the size and form of the tree), ii) Thinning out (to improve aeration),
and iii) Selective pruning (to cut off infested parts of the tree, especially, after
Phytophthora infections or citrus greening).
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11. Insect-Pests and their Management
A signicant number of insect-pests have been reported as being associated
with mandarin trees and causing serious impacts to the plants throughout the
year. The common insects are leaf minor, citrus trunk borer, twig borer, mealy
bug, aphid, citrus psylla, lemon buttery, bark eating caterpillar, citrus scale,
etc. The incidence and intensity of these pestsvary from region to region and
at different elevations.
11.1. Citrus Trunk Borer (Anoplophora versteegi Rits.)
At mid-altitude, this is the most serious pest of mandarins. In all citrus
growing belts of the region, mortality rates of 20–30 per cent have been observed
in both young and old orchards. Eggs are laid by making a T-shaped incision
near the collar region of the trunk. The base of the trunk is the preferred location
for egg laying. Oviposition has been observed on thick branches near crouches
or places of branching on occasionally, and eggs have been found up to 2 m
from the base of the stem. At the point of egg laying, plant sap starts oozing out,
which gives an indication of oviposition. Eggs take 10–12 days to hatch, and
grubs feed on the bark, where they remain feeding the bark for up to one and
a half months. After which they enter into the wood, making zig-zag tunnels
and blocking the transport system, thus killing the plants. The frass is always
pushed out of the entrance hole, which keeps the feeding zone free of any
feces matters. The presence of two or more grubs kills the plant within a year.
The grubs feed from May to September, pupate within the trunk, and emerge
as adults during the following March and April. The grubs de-bark the collar
region of the trees, leading to a stoppage of food supply to the plant. Due to
secondary infection by fungus and bacteria, the collar tissue rots, leading to the
complete death of the plant.
11.2. Bark Eating Caterpillar (Inderbela spp.)
Inderbela quadrinotata and I. tetraonis are widely distributed throughout the
region but are a serious pest in Meghalaya, Mizoram, Assam, and Arunachal
Pradesh. These insects have been found to be serious pests of citrus trees,
especially in neglected and old orchards, with poor management as compared
to newly established and well-maintained ones. Grubs feed on the trunk portion
during the evenings and nights. They make holes in stems and limbs for hiding
and cut the phloem vessels by feeding on bark under the cover of their webbing,
which consists of silken threads, frass, and excreta pellets.
11.3. Leaf Miner (Phyllocnistis citrella)
Larvae feed in the epidermis of leaves, making zig-zag galleries, which are
coloured silver because of entrapped air. The leaves become distorted, crumpled,
and gradually dry up. A serious attack may cause defoliation. This insect mostly
attacks newly emerged leaves during the ushing season.
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11.4. Citrus Psylla (Diaphorina citri)
A small brown ying insect rests on leaves with closed wings and the hind
end raised upward, the body making a 30o angle with the leaf. Both nymphs
and adults sucking the plant sap cause acute curling of the leaves, defoliation,
and death of the affected branches. The nymph also secretes whitish honeydew,
which serves as a medium for fungal growth. The photosynthesis of the plants
is affected. This insect also serves as the vector of the citrus greening bacterium.
11.5. Citrus Aphids (Toxoptera spp.)
Two citrus aphids commonly attack citrus crops, viz., brown citrus
aphid (Toxoptera citricida Kirkaldy) and black citrus aphid (Toxoptera aurantii
Fonscolombe. The aphids infest the lower side of leaves, tender branches, and
young fruits. The leaves and tips of the twig curled but were not chlorotic.
In severe cases, the ripening of the fruit is either slowed down or entirely
prevented. The black citrus aphid has proven to be a very efcient vector of
the Tristeza virus.
11.6. Citrus Mealy Bug (Pseudococcus filamentosus)
Adults as well as nymphs suck cell sap from leaves, shoots, and branches
during the spring season. The insect also settles on fruits. The nymphs are
amber-colored with a white waxy coating and laments around the margin. It
is females and nymphs that are commonly observed on plants; these are found
on the underside of the leaves in the form of clusters. Plants turn pale, wilt,
and eventually die as a result of sap loss. Simultaneously, they excrete large
amounts of honeydew, on which grows a sooty mold fungus. This fungus
covers the foliage and fruits, disrupting the plant’s normal functioning .In severe
infestations, the owers do not form fruits.
11.7. Citrus Scales (Aoinidiellia aurantii and A. orientalis)
All parts except the roots are infested by scales. Due to the attack, the leaves
turn yellow, become bristly, and fall off. Fruits become mottled and shriveled,
and shoots and twigs wither.
11.8. Citrus butter fly (Papilio demoleus L, P. helenus, P. protenon)
Several species of lemon buttery are of common and regular occurrence
pests. The caterpillars feed voraciously on leaves, leaving behind midrib only.
In general, they start feeding from the margin inward, reaching the midrib.
11.9. Fruit Sucking Moth (Otheris maternal L, O. fullonica L, O. ancilla L.)
The caterpillar has a dark brown velvety colour and is cylindrical, stout,
and semilooper. Adult moths pierce their proboscis into the fruit and suck the
juice. This not only causes fruit to drop but also exposes the fruit to bacterial
or fungal infection, causing the fruit to rot and suffer greatly in quality due to
the scar left on it if the wound it caused heals.
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12. Diseases Management
Greening disease, damping off, tristeza virus, anthracnose, Phaeoramularia
fruit, and leaf spot, gummosis, canker, and scab are all major diseases
contributing towards citrus decline.
12.1. Phytophthora Rot
Among the soil-borne pathogens, Phytophthora spp. is the major problem
reported all over the citrus-growing regions and is also referred to as foot rot,
root rot, crown rot, collar rot, trunk rot, and gummosis. Three species, viz.,
P. citrophthora, P. nicotiannae, and P. palmivora, are mostly responsible for the
decline, low productivity, and short life span of citrus plants. Heavy and poorly
drained soil, excessive irrigation, the use of susceptible rootstock, and prolonged
water stagnation near the trunk predispose the plant to soil-borne diseases. The
rst indication of the disease is the exudation of gum from the bark of the trunk.
The bark cracks open and, in the later stage, dries up and falls off, exposing the
wood to secondary infection by other organisms.
12.2. Twig Blight (Colletotrichum gloeosporioides)
It is a serious and widespread citrus problem in the North-East. The affected
plants exhibit drying of twigs and small branches from the growing tip and die
back, leading to reduced plant canopy and yield. Affected plants exhibit more
fruit drop, and even harvested fruits show a high percentage of stem end rot
during postharvest storage.
12.3. Citrus Scab
This disease is widely prevalent in the north-eastern region of India,
infecting leaves, shoots, and fruits. Newly emerged leaves are most susceptible
but develop resistance with maturity. On young leaves, lesions start as small,
elevated, pale orange spots, becoming sharply dened. With the hardening of
the leaf, the lesions become rough, corky, wart-like, and brown to dark brown
in colour. Affected leaves become distorted, wrinkled, stunted, and misshapen.
Fruit remains susceptible for up to 3 months after it sets. Lesions on the fruits are
corky and have projections, which become brittle and break into incrustations.
The pathogen survives in the scab and pustule and initiates infection on new
ushes. Synchronous attacks of the leaf-miner insect further help in causing
distortion of the infected parts more severely.
12.4. Powdery Mildew
A white cottony or powdery growth appears on all parts of the affected
plant. The young leaves crinkle, turn yellow, and have distorted margins.
Prominent blisters, cupping, and curling of the leaves take place. In severe
conditions, the cottony growth becomes black, leading to premature leaf and
fruit fall. Infected owers start shedding, and affected fruits also turn black and
Organic Cultivation of Citrus (Citrus spp.) | 161
drop off. Infected twigs exhibit dieback symptoms. Due to the death of growing
shoots, many lateral shoots develop, causing a bushy appearance.
12.5. Sooty Mold
Black, moldy growth develops on honeydew secreted by insects like aphids,
scales, and mealy bugs. No parasitism is observed in the citrus, but the presence
of the black mating of mycelium may affect photosynthetic activity. The affected
young fruit does not develop because of the black coating.
12.6. Greening Disease
This disease affects all three-commercial species of citrus: sweet orange, acid
lime, and mandarin orange. The disease is caused by a Rickettsia-like organism.
It spread through the use of disease buds and the insect vector, citrus psylla.
A characteristic symptom of the disease is the growth of small, leathery leaves
with interveinal chlorosis and the distribution of green islands on a yellow area.
Leaves drop prematurely.
12.7. Management Strategies of Insect-Pests and Diseases
Pest and disease management in citrus fruits under an organic production
system can be achieved with the effective adoption of preventive measures to
avoid heavy infections. Effective pest and disease management in citrus organic
production systems is an integrated approach and forms an integral part of
overall management approaches combining cultural, mechanical and biological
strategies in the rst place and using botanical and organically acceptable
chemicals only as a last resort (Shree, 2022).
The rst and most important strategy for organic pest management in
citrus fruits is the choice of suitable varieties for the scions and rootstocks that
are adapted to the local climatic conditions, increasing plant resistance to pests
and diseases.
The second stepis promoting and maintaining of habitat diversity including
organic orchard design, which comprises permanent diversity plantation on
the boundary and internal bunds, as well as seasonal diversity through cover
crops, intercrops, blooming plants, and agroforestry trees that enhance natural
enemies of pests and trap crops.
The third approach involves the manipulation of cultural practices to
ensure a balance in natural processes, which in turn keep the pests below the
economical threshold limit.
The fourth step involving regular monitoring of the orchard allows early
identication of infections and timely intervention before major damage occurs.
Pruning and de-suckering increase the aeration of the orchard. Removal and
destruction of infected plant parts reduce pest and disease pressure in the
orchard.
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The cultural and ecological management pronged strategies are the most
commonly follow.
A. Cultural Strategies
Proper cultivar selection is necessary to assure disease-free and resistant
cultivars. Adopt suitable cultural methods such as spacing, mulching, and
green manuring, as well as the proper use of organic manures and irrigation.
Avoid high-density planting to avoid overcrowding. The frequent growing
of legume cover crops and their mowing with soil. Maintaining soil cover
with living vegetation or crop residue. Adequate use of organic manures is
followed by biomass mulching and drenching with fermented dung-urine
slurry (such as Jivamrit). Bio-fertilizers, particularly mycorrhiza and PGPRs, are
used frequently. Frequent drenching of tree basins (at least once a year) with
Trichoderma viride, T. harzianum, and Pseudomonas uorescens. Avoid growing
host plants such as Murraya koenigii (curry leaf) in and around citrus plantations.
B. Ecological Strategies
At the nursery stage, the seedlings or budded or grafted plants need to
be protected against insect-pests and diseases using botanical pesticides such
as neem oil or any other available formulation for insect-pests. In established
citrus, adopt a permanent diversity plantation to ensure natural habitat and
survival conditions for natural pest enemies such as pest predators, parasites,
and pathogens. This can be done by growing 2-3 citrus varieties between the
main variety, nitrogen-xing plants like Gliricidia and Leucaena leucocephala
on borders, and pesticidal value plants like adathoda, Ipomea, Calotropis, etc.
randomly in between border plantations and aromatic grasses like lemon and
citronella grass on bunds. Seasonal diversity includes intercrops and cover crops.
Some owering trap crops, such as marigold, mustard, sunower, alfalfa, carrot,
French bean, cowpea, maize, spearmint, peppermint, coriander, Ocimum, etc.,
can be planted. Do not uproot weed plants; those are growing naturally and act
as nectar sources for natural enemies. Due to the enhancement of biodiversity
by the owering plants, the number of parasitoids and predators (natural
enemies) will also increase due to the availability of nectar, pollen, insects, etc.
The major predators are a wide variety of spiders, ladybird beetles, long-horned
grasshoppers, Chrysoperla, earwigs, etc.
Collect egg cards of benecial insects for release, such as Trichogramma,
Chrysoperla, and Telenomus. Install 4-5 pheromone traps for monitoring and
10–12 traps for mass trapping of moths. Set up yellow pan water traps and sticky
traps 15 cm above the canopy for monitoring whitey and blue sticky traps for
thrips at 10–15 traps/acre. Set up light traps (1–2 traps per acre) 15 cm above the
crop canopy for monitoring and mass trapping of insects. Light traps with an
exit option for natural enemies of smaller size should be installed and operated
around dusk (6 p.m. to 10 p.m.). Keep on monitoring the pest-defender ratio.
There is no need to be concerned if the pest-to-defender ratio is 2:1.
Organic Cultivation of Citrus (Citrus spp.) | 163
C. Mechanical Management
To control the citrus buttery, larvae must be handpicked and killed. Spray
the Nimbecidine @ 5-6 ml/L of water during the ush period to manage citrus
scales. Spraying with a 1 per cent Bordeaux mixture was found effective to
manage diseases. Avoid water stagnation around the plants. Scrap the affected
portions and apply Bordeaux paste. Remove the soil around the trunk and
drench the root with a 1 per cent Bordeaux mixture to reduce diseases. The
collection and destruction of adults of the bark-eating caterpillar during May
by shaking the branches 2-3 times at a 10-day interval is a simple and effective
control measures. To kill the trunk borer grubs, clean the bored hole of the
infested plant with iron wire and insert a cotton swab soaked in petrol, or inject
5 ml of petrol and plug it with mud. Cut the affected branches of the insect-
eating tree and apply Bordeaux paste at the pruned portion. Natural pesticides
such as pyrethrum, derris, neem, soaps, mineral, and plant oils, as well as mass
trapping techniques, are used in organic citrus production. Routine sprays
with protective organic fungicides such as copper-based fungicides (Bordeaux
mixture, and Lime) can protect nursery and eld plants from disease control.
13. Harvesting and Yield
The external fruit quality and peel colour have been found to be highly
correlated with fruit palatability (Lado, 2014). Color is a key aspect of the quality
of citrus fruits, inuencing consumer perception and acceptability. The rich
variation of citrus fruit pigmentation is tightly linked to carotenoid content
(Rodrigo et al., 2013). Carotenoid content and composition are responsible for
the diverse range of colour tones displayed by fruits of various species: ranging
from pale yellow to red in white and red grapefruits, to dark yellow in lemons,
orange in sweet oranges, and an intense orange coloration in some mandarins
and hybrids. Mature oranges have a higher concentration of xanthophylls.
Mature lemon fruit is distinguished by its yellow colour, which ranges from
greenish-yellow to bright yellow depending on the cultivar. Only lime fruits
have a marketable colour that is preferably green; in such circumstances, the
primary pigments providing colour are chlorophylls.
Citrus fruits have a non-climacteric ripening behaviour and should be
harvested when internal maturity is attained, as no further important changes
in the fruit’s composition occur after harvest. Throughout the growth and
development of citrus fruits, sugar and pigments accumulate in the pulp of
fruits, while acid content declines. As a result, the sugar/acid ratios varied
during ripening, which is usually used as a key important maturity indicator.
If the fruits are attached to the trees for a prolonged period of time, the acid
content declines substantially concurrently with increasing sugar accumulation,
resulting in the loss of the fruit’s unique avour and taste, making it insipid and
more susceptible to degradation. TSS is a very practical indicator of internal
fruit quality and an accurate criterion for harvest decisions in the eld because
Organic Culture of Tropical and Subtropical Fruit Plants
164 |
its content continues to rise throughout ripening. This is especially important
to accurately assess the maturity of fruits. Fruit juice content is similarly related
to the ripening process, as it increases as the fruit matures to the highest value
at full maturity and then falls. The criteria for using this quality measure as
a commercial standard index varies according to citrus species and market
destination. Other commonly quantiable parameters, such as size or weight,
are not always reliable indications of fruit maturity; yet, they are critical quality
parameters in fruit commerce and marketability. Lately, a new concept of
“nutritional” and “sensorial” harvest indices has been emphasized in organic
citrus fruits. This concept identies the content of several bioactive compounds
associated with avour and health as important features for marketability and
differentiation in fruit quality (Obenland et al., 2009). Citrus maturity indices
can vary considerably depending on the growing areas, markets, and varietals.
The primary maturity indices for citrus quality in the EU are juice content,
total soluble solids, TSS:acid ratio, and the proportion of the fruit surface with
distinctive coloring (Anon., 2010).
Mandarin (Citrus reticulata)
Mandarins are considered mature in India when they have attained: at
least 75 per cent of the typical mature fruit surface coloration (yellow-orange
coloration), acidity (0.3-0.4 per cent), TSS (at least 8.5 per cent), and the TSS:acid
ratio (least 6.5) (Tiwari, 2006). In India, sweeter fruits are preferred; a TSS: acid
ratio of 14 is recommended as a minimum for optimum eating quality. For
“Nagpur” mandarins, for instance, harvesting is advised when 8.3 per cent
TSS and 0.8 per cent acidity are reached. TSS/acidity ratios range from 10 to 14
units depending on the Mandarin(Ladaniya, 2008). In Khasi mandarin, fruits
are ready for harvesting during the months of November and January.
Sweet Orange (Citrus sinensis)
In sweet oranges, the TSS:acid ratio has been considered a more reliable
index than peel coloration, since important changes occur in external color
development depending on temperature and humidity conditions (Ladaniya,
2008). In India, the minimum TSS content for a harvest to be considered
acceptable has been set at 12–13 oBrix, with a ratio of 10–14 for the majority
of orange types. With a minimal acidity level of 0.4-0.7 per cent for a superior
taste, higher ratios have also been standardized in Indian cultivars during later
seasons, ranging from 13 to 22.
Lemon (Citrus limon)
The TSS/acid ratio is not considered a suitable maturity index for lemons,
in contrast to oranges and mandarins. As a result, time after fruit set and, in
particular, total juice content is commonly used as maturity indicators in lemon
fruits. In India, a ripening period of 165 to 195 days with more than 50 per cent
juice content and a total acidity of 9 per cent are considered good indicators of
mature fruit (Ladaniya, 2008).
Organic Cultivation of Citrus (Citrus spp.) | 165
Grapefruit (Citrus paradisi)
Grapefruit maturity standards vary with the growing regions and among
red, pink and white varieties as give in Table 7.11.
Table 7.11: Maturity Indices of different Citrus Fruits
Species/
Varieties
TSS Acidity TSS :
Acid
Colour
(Fruit
Surface)
Juice
Content
References
Mandarin
India ≥ 8.5 per
cent
0.3-
0.4
per
cent
≥ 6.5 ≥ 75
per cent
yellow-
orange
Tiwari, 2006
8.3 per
cent
0.8
per
cent
10-14 Mazumdar,
1976; Ladaniya,
2008
California ≥ 6.5 ≥ 75
per cent
yellow-
orange
Arpaia and
Kader, 2000
Australia ≥ 8 oBrix > 8 28 per
cent
Walsh, 2013
Europe ≥ 6.5-7.5 ≥ 33-40
per cent
EU, 2011
Uruguay 9 ºBrix 7-8 ≥ 40 per
cent
MMUK, 2014
South Africa 8.5 ºBrix 7.5-8 ≥ 48 per
cent
DAFF, 2011
Sweet oranges
Florida ≥0.4-
0.5
per
cent
8-10 ≥25 per
cent
yellow-
orange
Soule et al.,
1986; Arpaia
and Kader,
2000
Cuba (var.
Valencia)
8-12 Aranguren et
al., 1992
Australia (Navel
oranges)
≥ 8 oBrix > 8 ≥ 33 per
cent
Walsh, 2013
European
(Navel oranges)
≥ 6.5 80 per
cent
typical
orange
≥ 33 per
cent
EU, 2011
Uruguay
(Valencia and
Navel oranges)
≥ 9 o
Brix
9≥ 40 per
cent
MMUK, 2014
Organic Culture of Tropical and Subtropical Fruit Plants
166 |
Species/
Varieties
TSS Acidity TSS :
Acid
Colour
(Fruit
Surface)
Juice
Content
References
South Africa
(Valencia and
Navel oranges)
≥ 8.5
oBrix
7 42-45 per
cent
DAFF 2011
Grapefruits
California
(Marsh
grapefruit)
≥ 6-7
oBrix
5.5-6 66 per
cent
yellow
color
35 per
cent
Annon., 2010
Marsh grapefruit
in Florida
≥ 7.5
oBrix
≥ 7 35 per
cent
Wardowsk et
al., 1979; UN,
2010
India (white
Marsh
grapefruit)
≥ 7 Randhawa et
al., 1964
Red Blush
grapefruit
≥ 11.8 Chohan et al.,
1984
South Africa ≥ 7 oBrix ≥ 5.5 40 per
cent
DAFF, 2011
Lemons
India 9 per
cent
165-195
days
≥ 50 per
cent
Ladaniya,
2008
Australia and
Morocco
≥ 25 per
cent
Walsh, 2013
California ≥ 8–30 per
cent
Arpaia and
Kader, 2000
Europe ≥ 20 per
cent
EU, 2011
Uruguay and
South Africa
35-36 per
cent
DAFF, 2011;
MMUK, 2014
Fruits of citrus should be harvested when they attain the criteria of maturity
indices. Harvesting of citrus for the fresh market is done by hand. Normally,
fruit is cut with hand clippers and collected in picking bags and then transferred
to eld containers and then transported to packing houses or collection centers
or transferred directly to the market. However, some sorting is usually done
during picking to eliminate defective fruits.
14. Post-harvest Handling of Citrus Fruits
Organic post-harvest management techniques can only be successful if
insect-pests and diseases are effectively managed in the pre-harvest stages. It
must be ensured that fruit grown using organic production approaches has
Organic Cultivation of Citrus (Citrus spp.) | 167
the least infection from insect-pests and diseases. This is crucial because no
fungicides are permitted in organic post-harvest treatment.
In a citrus pack house, the sequence of events can be (i) receiving in the
pack house (ii) de-greening if required (iii) dumping and trash removal (iv)
sorting including removal of diseased and small fruits (v) washing and rinsing
(vi) waxing (vii) drying (viii) sizing (ix) carton lling and labeling (x) palletizing
(xi) pre-cooling and storage and (xii) container loading.
15. Economics of Production
15.1. Cultivation Costs
The economic sustainability of organic citrus production in comparison
to conventional systems may provide a clearer picture of the protability of
the system. Torres et al. (2016)found that conventional citrus production had
lower annual variable costs (2185 €/ha) than organic systems (4147 €/ha for
Sweet Orange cv. Navelina), which is 47 per cent lower than organic farming.
In terms of variable costs, conventional cultivation is more cost-effective,
particularly with regard to irrigation and fertilizers. This is due to the fact that
organic fertilizers are more costly than synthetic fertilizers. Crop protection
management in organic farming, on the other hand, is limited to mineral oils,
which are primarily used for fresh consumption. The other cost variables, which
include orchard oor management practices and labour, are higher for organic
practices due to the additional attention they require, particularly for fresh
consumption (Torres et al., 2016). Similarly, according to Igual and Izuierdo
(2000), the organic production costs are higher (27.9 per cent for oranges and
25.9 per cent for mandarins) and yields are lower, notably during the conversion
period (19.4 per cent for oranges and 19.6 per cent for mandarins). The nancial
viability analysis of Khasi mandarin under organic production in the north-
eastern Hills revealed that the yield was 74112 (number of fruits per ha), Net
Return (Rs. 71,441/ha), BC ratio (2.08) and the payback period was 7.5 years
(Mohanty et al., 2015).
15.2. Profitability and Expected Income
Organic fruits of “Navelina,” both fresh and processed, fetched a higher
price than conventional products. The price per kilogram for organic and
conventionally produced oranges is the same due to the fact that both practices
grow conventionally over the rst 11 years. In the post-conversion period to
organic farming, signicant increases in sales pricing of organic fruits were
noticed. The higher organic production costs reveal the need for a high sale
price of produce to be protable. In “Bajo Andarax” District (Spain), the prices
of organic citrus fruits of “Navelina” were 425 per cent higher than “Navelina”
under conventional practices. The net present value (NPV) value of sweet
oranges was positive in organic practices (12,024 €/ha) with an 11 per cent
internal rate of return (IRR). Furthermore, the investment was recovered in 15–16
Organic Culture of Tropical and Subtropical Fruit Plants
168 |
years under an organic production system (Torres et al., 2016). Contradictory,
Igual and Izuierdo (2000) revealed that higher protability in conventional
citrus farming than in organic systems, as well as the greater sensitivity of
organic orange growing to variations in market prices. As a result, it indicates
that organic citrus production can only be protable where there is a strong
preference for organic fruits, with 30–40 per cent higher pricing for organic
citrus than conventional citrus (Igual and Izuierdo, 2000).The higher consumers’
preferences for organic lemons are due to improved avour, sourness and lemon
fragrance under organic system. Such attributes appealed to the consumers
for the most liked ones (78 per cent), consumers willing to pay (50 per cent vs
only 33 per cent for conventional lemons) (Sanchez-Bravo et al., 2022). To boost
the protability of organic citrus fruits for the fresh market, it is necessary to
complete the conversion period at the earliest for early returns. It is also vital to
increase the quality of the organic fruits, even if it means increased production
costs, in order to reduce the inferior fruits, which is critical for price settlement
for the product between the growers and the buyers. The discarded fruits
instead of selling at throwaway prices, should be valorized into organic fruit
juice, thus, resulting in more income.
16. Marketing and Organic Certification of Citrus Production
Citrus fruits are the most preferred of the several organic product categories.
Orange (Citrus sinensis (L.) Osbeck) is the most consumed organic fruit in the
EU, followed by banana (Musa spp. L.).Organic citrus cultivation currently
accounts for less than 2 per cent of total global citrus production. However, it is
expanding year after year in accordance with the growing demand for organic
products. The European Union and the United States are the two primary
markets, as well as the world’s two largest producers. In recent years, supply
has expanded dramatically. There is no information available on the sales value
of organic fresh citrus fruits. However, it is estimated that these account for 5
per cent to 7 per cent of fresh organic food sales, which is approximately $70
million to $100 million/year globally. In terms of volume, the EU was predicted
to consume more than 130,000 t of certied organic citrus in 2000.This gure
excludes organic citrus fruit that was not certied, which might account for
one-third of EU organic citrus output. According to Hamm et al. (2002), the EU
consumed over 350,000 t of fresh certied organic fruit in 2000, with citrus fruits
accounting for 37 per cent of that total (Liu 2003). Italy and Spain dominate the
EU market for fresh organic citrus such as oranges, tangerines (Citrus tangerine
L.), and lemons (Citrus limon (L.) Burm.f.).In addition to fresh organic citrus
fruits, there is also a growing demand for organic citrus juices, which account
for 0.3 per cent of total citrus juice consumption (Liu, 2003).
17. Organic Certification
The organic farming sector in India is growing, but it is beset by fraudulent
and malpractice, such as the sale of inorganic products as organic on the
Organic Cultivation of Citrus (Citrus spp.) | 169
domestic market (Vishwa Mohan. 2017). Moreover, the aws with the organic
regulatory framework continue to hinder the organic industry and Indian
exports (USDA, 2021).
17.1. Procedure for Obtaining Organic Farming Certification
The following are the different steps to obtain organic farming certication
for citrus products. Apply in the requisite format along with the fee and complete
eld verication. Before submission of the application, the applicant or farmer
must adhere to the standard laid out by the NPOP for organic crop production
(India Filling, 2023).
Step-1: General organic farming requirements: A citrus orchard must
conform to the standards set out by the NPOP to obtain the Organic Farm
certication. Prepare, implement, and update annually an organic production
plan. Permit on-site inspections with complete access to the production and
handling operation, including non-certied production and handling operation,
areas, structures, and ofces by the Organic Certication Inspectors and other
higher ofcials, whenever required. Maintain all records applicable to the
organic operation for not less than 5 years. After the creation of such records
allow authorized representatives of the certication body, State or Central
Government ofcials of accrediting agency access to verify such records during
normal working hours for review and copying to determine compliance with
NPOP norms. Pay the prescribed fees charged for organic farming accreditation
within the stipulated time. The authorities must be informed whenever a
prohibited substance is used during the course of production. Similarly, if any
changes are made to any components of certied operations that may have an
impact on the organic integrity in accordance with NPOP standards must also
be notied to the authorities.
Step -2: Applying for Organic Farm Certication: Once the requirements
for organic citrus production are satised, the applicant can prepare and
apply. The application for certication must contain information on an organic
production or handling system plan, full information in the application,
prescribed registration fee, etc.
Step 3: Review of Application: On submission and review of the
application, the decision of acceptance or rejection of the application would be
taken by the accreditation authority.
Step 4: Scheduling of Inspection: Before sanctioning of accreditation, an
initial eld inspection would be xed at a reasonable time so that the operator can
verify the capacity to comply with the standards while conducting the inspection
of land, facilities, and activities. There should be one annual inspection and
additional inspections can be xed based on the risk assessment carried out
during the initial inspection.
Organic Culture of Tropical and Subtropical Fruit Plants
170 |
Step 5: Verification During Inspection: During field inspection, the
concerned authorities would verify the compliance with the NPOP standards.
Step 6: Granting of Organic Farm Certication: On conformance with the
NPOP, the accreditation agency would issue the Certicate of Registration,
Transaction Certicate and Product Certicate to the eligible operators as per
the decision made by the certication committee.
Step 7: Continuation of Certication: The operator shall renew registration
by paying fees for renewal to continue certication.
18. Challenges Related to Organic Citrus Production
P Inferior varieties: The non-availability of quality planting materials
such as certied and vegetatively propagated materials, growers
resorted to using inferior planting materials such as seedlings, which
may yield low yields and be susceptible to disease.
P Lack of scientic know-how: Due to drought and poor management,
poor yields often result. Most citrus production is done in small
gardens mainly for the domestic market. The crops are not irrigated
and, in most cases, suffer from drought stress, delayed owering,
affecting potential yields.
P Lack of policies: Organic farming still receives insufcient research
and extension assistance in several countries. Organic production
inputs are often lacking in such countries.
P High pests and diseases incidence: Citrus plants are extremely
vulnerable to a wide range of insect pests and diseases. Thus,
management is extremely challenging due to the little advancement
made in the development of effective insecticides and protective
compounds.
P Post-harvest handling: Harvesting of premature and overripe fruit,
mechanical damage during harvest, transport, and distribution, water
loss (wilting) due to a poor handling system, infection with mold and
fungus, and insect damage all contribute to large post-harvest losses.
P Economic challenges: For the majority of citrus growers, economic
and commercial concerns are the most crucial factors in the choice to
shift to organic production. Conversion to organic farming is always
associated with the future development of a farm and enhancing the
farmer’s income. Intensive organic management system required
additional labour, high investment, high production cost, etc.
P Certification: Product certification is essential for a product to
be recognized as of premium quality and priced accordingly. An
independent agency executes certication, which is required for market
access. As part of the certication process, certied organic growers
must demonstrate that their orchard oor management practices
Organic Cultivation of Citrus (Citrus spp.) | 171
correspond. Fullling quality criteria and dealing with certication
issues is a major challenge in developing countries. Furthermore,
certication requires massive nancial involvement.
P Marketing and trade challenges: Consumers are aware of the benets
of organic food, and demand for organic products is increasing
globally. The organic market is particularly specic, and marketing
organic products requires accurate information as well as market
access criteria. However, due to a lack of certication agencies and an
unregulated market, inexperienced growers and retailers were unable
to sell their products at the desired price.
19. Prospect and Future Scopes
Organic certied citrus continues to play a limited role in regions other than
Europe. The north-eastern part of India grows citrus organically by default,
with little or no pesticide input, primarily for the local market. Nonetheless,
the market provides tremendous prospects for future expansion. The choice
to certify citrus production should be based on market potential, ecological
demands, and consumer needs. There is a need for the development of
favourable institutional frameworks, agricultural regulations, and organic
distribution networks. This will result in greater organic commodity prices, as
well as increased interest among growers, hence promoting organic production
systems. Organic cultivation, which requires a huge workforce, provides a
socio-economic opportunity as it may generate higher incomes. To promote
organic citrus growers, greater emphasis must be placed on strengthening
farmers through technical training and education. In the near future, organic
citrus production will expand, but how quickly will depend on market dynamics
and the practical impact that institutional support has on the citrus-growing
industry.
REFERENCES
Abouziena, H.F., O.M. Hafez, I.M. EL-Metwally, S.D. Sharma and M. Singh,
2008. Comparison of weed suppression and mandarin fruit yield and
quality obtained with organic mulches, synthetic mulches, cultivation, and
glyphosate. Hort. Sci., 43(3): 795-799.
Albiach, R., R. Canet, Pomares, F. and Ingelmo, F. 1999. Structure, organic
components and biological activity in citrus soils under organic and
conventional management. Agro-chimica, 43(5/6): 235–242
Anonymous. 2010. UN. Unece Standard FFV-14. Citrus fruit. New York and
Geneva; 2010 p.12.
APEDA. 2022. National Programme for Organic Production (NPOP). https: //
apeda.gov.in/apedawebsite/organic/organic_products.htm. Accessed on
22.12.2022
Organic Culture of Tropical and Subtropical Fruit Plants
172 |
APEDA. 2023a. Appendix I-Organic Crop Production. https: //apeda.gov.
in/apedawebsite/organic/organic_contents/Appendix_1_Crop per cent
20Production.pdf (Accessed 18.01.2023).
Aranguren M, Lopez B., Rodriguez J., Suarez C and Zayas J. 1992. Maturity
calendar and harvest organization for Valencia in Jaguey Grande, Cuba.
Proceedings International Society of Citriculture; 1992: pp. 1023-1025.
Arpaia M and Kader AA. 2000. Produce facts (grapefruit, lemon, mandarin,
orange)-Recommendations for maintaining postharvest quality. http: //
postharvest.ucdavis.edu/PFfruits. (Accessed June 18, 2014).
Avasthe, R. K., Pradhan, Y. and Bhutia, K. 2014. Handbook of organic crop
production in Sikkim. Sikkim Organic Mission, Govt. of Sikkim and ICAR
Research Complex of NEHR, Sikkim Centre, Gangtok.pp. 161-172.
Beltran-Esteve, M., Picazo-Tadeo, A.J. and Reig-Martínez, E. 2012. What makes
a citrus farmer go organic? Empirical evidence from Spanish citrus farming.
Working Papers in Applied Economics. WPAE-2012-05, ISSN 2172 3036.
pp. 1-26.
Canali S. 2003. Soil quality of organically managed citrus orchards in the
Mediterranean area. Organic agriculture: sustainability, markets and
policies. OECD/CABI Publishing, Paris/Wallingford
Canali, S., Di Bartolomeo, E., Benedetti, A., Intrigliolo, F., Calabretta, M. L.,
Giuffrida, A. and Lacertosa, G. 2002. Soil fertility status of conventional and
organic managed citrus orchards in Mediterranean area. In 7. International
Meeting on: Soils with Mediterranean Type of Climate, Valenzano (Italy), 23-28
Sep 2001. CIHEAM-IAMB.
Chohan GS, Dhillon BS and Josan JS. 1984. A note on the performance of Red
Blush grapefruit in the arid-irrigated region of Punjab. Punjab Horticultural
Journal, 24: 46-48.
DAFF 2011. Department of Agriculture, Forestry and Fisheries, Directorate Food
Safety and Quality Assurance. Export Standards and Requirements. South
Africa. http: //www.daff.gov.za; 2011: (Accessed June 18, 2014).
de Castro, Danielle dos Santos Bonm, Lana de Souza Rosa, Ellen Mayra da Silva
Menezes, and Anderson Junger Teodoro. 2014. Comparative evaluation
of organic and conventional farming on chemical quality parameters
and antioxidant activity in fruits. African Journal of Biotechnology, 13(8):
DOI: 10.5897/AJB2014.13632
Duarte, A. M., Caixeirinho, D., Miguel, M. G., Sustelo, V., Nunes, C., Fernandes,
M. M., and Marreiros, A. 2010. Organic acids concentration in citrus
juice from conventional versus organic farming. In XXVIII International
Horticultural Congress on Science and Horticulture for People (IHC2010). pp.
601-606.
Organic Cultivation of Citrus (Citrus spp.) | 173
Ennab, H. A. and El-Sayed, S. A. 2014. Response of balady mandarin trees to
decit irrigation. J. Agric. Res. Kafrelsheikh Univ, 40(3): 616-629.
EU. Reglamento de ejecucion (UE) No 543/2011 de la Comision de 7 de junio
2011.Ofcial Journal of the European Union; 2011: L157: 71-75.
EUROSTAT. 2012. Statistical information. http: //epp.eurostat.ec.europa.eu/
portal/page/portal/statistics/search_database Accessed 3-9- 2012.
EUROSTAT. 2021. Organic Farming Statistics. Available online: https: //
ec.europa.eu/eurostat/statistics-explained/index.php?title=Organic_
farming_statistics (accessed on 15 May 2021).
FAOSTAT. 2009. http: //faostat.fao.org/site/567/DesktopDefault.
aspx?PageID=567#ancor. Accessed 11 July 2011
FiBL 2011. African Organic Agriculture Training Manual. Version 1.0 June
2011. Edited by Gilles Weidmann and Lukas Kilcher. Research Institute of
Organic Agriculture FiBL, Frick.
Futch SH and Singh M. 2010. Florida citrus pest management guide. In: Weeds
(Eds. Rogers ME, Dewdney MM, Spann TM). pp. 125-137.
Galindo, A.; Noguera-Artiaga, L.; Cruz, Z.N.; Burló, F.; Hernández, F.;
Torrecillas, A. and Carbonell-Barrachina, T.A. 2015. Sensory and physico-
chemical quality attributes of jujube fruits as affected by crop load. LWT-
Food Sci. Technol., 63: 899–905.
Green Petersen, D. M. B. and Hyldig, G. 2010. Variation in sensory prole of
individual rainbow trout (Oncorhynchus mykiss) from the same production
batch. Journal of Food Science, 75(9): S499-S505.
Hamm U, Gronefeld F, Halpin D. 2002. Analysis of the European market for
organic food. Dissertation, University of Wales Aberystwyth, Aberystwyth
Igual, J., andIzquierdo, R. 2000. Economic and nancial comparison of organic
and conventional citrus-growing systems in Spain. Horticultural products
Group, Commodities and Trade Division, FAO (Rome). pp. 1-48.
India Filling. 2023. Organic Farming Certication in India. https: //www.
indialings.com/learn/organic-farming-certication-in-india/. (Accessed
18.01.2023)
Johnson, W. C., and Davis, J. W. 2014. Pelargonic acid for weed control in organic
Vidalia® sweet onion production.Hort. Technology, 24(6): 696-701.
Kilcher L 2005. Organic citrus: challenges in production and trade. In: Cuaderno
de Resumenes I ConferenciaInternacional de CitriculturaEcologica
BIOCIITRICS, pp 22–27.
King, B. M., Duineveld, C. A. A., Arents, P., Meyners, M., Schroff, S. I., and
Soekhai, S. T. 2007. Retronasal odor dependence on tastants in proling
studies of beverages. Food Quality and Preference, 18(2): 286-295.
Organic Culture of Tropical and Subtropical Fruit Plants
174 |
Kour, G. and Bakshi, P. 2018. Irrigation management practices and their inuence
on fruit agroecosystem. In: Irrigation in Agroecosystems (Ed. Gabrijel
Ondrašek). IntechOpen. DOI: 10.5772/intechopen.79569
Kremer, R. J. 2019. Soil health benets of the solar corridor crop system. In: The
Solar Corridor Crop System (pp. 79-101). Academic Press.
Ladaniya MS. 2008. Growth, maturity, grade standards and physic-mechanical
characteristics of fruit. In: Citrus fruit, Biology, Technology and Evaluation.
Ladaniya MS (editor). USA: Academic Press; pp.191-212.
Lado, J., Rodrigo, M. J., and Zacarías, L. 2014. Maturity indicators and citrus
fruit quality. Stewart Postharvest Review, 10(2): 1-6.
Lester, G.E., Manthley, J.A. and Buslig, B.S., 2007. Organic vs. conventionally
grown Rio Red whole grapefruit and juice: comparison of production
inputs, market quality, consumer acceptance, and human health-bioactive
compounds. J. Agric. Food Res., 55: 4474-4480.
Levy, Y., and B. Boman. 2003. “Water Management in Citrus. https: //www.
researchgate.net/publication/293334460_Water_Management_in_Citrus
(Accessed on 20.12.2022)
Liu P 2003. World markets for organic citrus and citrus juices – current market
situation and medium-term prospects. FAO, Rome. http: //www.fao.org/
DOCREP/006/J1850E/j1850e00.htm#. Last Accessed 20 sept 2011
Manera, J.; Brotons, J.M.; Conesa, A.; Porras, I. 2012. Relationship between air
temperature and degreening of lemon (‘Citrus lemon’ L. Burm. f.) peel color
during maturation. South. Cross J., 6: 1051–1058.
Mattos D, Quaggio JA, Cantarella H et al., 2006. Response of young citrus trees
on selected rootstocks to nitrogen, phosphorus and potassium fertilization.
J Plant Nutr., 29: 1371–1385. doi: 10.1080/01904160600830159
Mazumdar B.C. 1976. Physico-chemical changes in fruits of ‘Kinnow’ and
‘Nagpur’ Santra during development and maturation. Punjab Horticultural
Journal, 16(3-4): 96-100.
Menino MR, Carranca C, de Varennes A. 2007. Distribution and remobilization
of nitrogen in young non-bearing orange trees grown under Mediterranean
conditions. J Plant Nutr., 30: 1083–1096. doi: 10.1080/01904160701394543
MMUK, 2014. Technical requirements southern hemisphere, season 2014.
MM(UK). Available in: http: //www.mmuk.co.uk/(Accessed June 18,
2014).
Mohanty Suchitra, Mandal Subhasis and Rahim KMB 2015. Economics of Hill
Farming System with special Reference to Feasibility and Constraints in
Production of Organic Commodities in Meghalaya India, paper presented
in International Conference on Managing Critical Resources: Food, energy and
Organic Cultivation of Citrus (Citrus spp.) | 175
Water, 9-11 April, 2015, Centre for Development and Environment Policy,
IIM, Kolkata.
Navarro-Martínez, Patricia, Luis Noguera-Artiaga, Paola Sánchez-Bravo,
Ema C. Rosas-Burgos, Antonio J. Pérez-López, and Ángel A. Carbonell-
Barrachina. 2019. Development and characterization of liquors prepared
with an underutilized citrus by-product, the peel. European Food Research
and Technology, 245: 41-50.
Obenland D, Collin S, Mackey B, Sievert J, Fjeld K and Arpaia ML. 2009.
Determinants of avor acceptability during the maturation of navel oranges.
Postharvest Biology and Technology, 52: 156-163.
Perez-Lopez, A.J., López-Nicolás, J.M. and Carbonell-Barrachina, A.A. 2007.
Effects of organic farming on minerals contents and aroma composition
of Clemenules mandarin juice. European Food Res., Technol., 225: 255-260.
Plantix. 2023. Damping off of seedlings (Pythium spp.). https: //plantix.net/
en/library/plant-diseases/100322/damping-off-of-seedlings. Accessed
on 14.03.2023.
Randhawa GS, Khanna RC and Jain NL. 1964. Seasonal changes in fruits
and bearing shoots of the grapefruit (C. paradisi Macf.). Indian Journal of
Horticulture, 21: 21-32.
Reganold, J. P., and Wachter, J. M. 2016. Organic agriculture in the twenty-rst
century. Nature plants, 2(2), 1-8.
Rodrigo MJ, Alquezar B, Alos E, Lado J and Zacarias L. 2013. Biochemical bases
and molecular regulation of pigmentation in the peel of Citrus fruit. Scientia
Horticulturae, 163: 42–62.
Rymbai, H., Talang, H. D., Rymbai, D., Mawleiñ, J., Devi, M. B., and Assumi,
S. R. 2022. Good orchard management practices in Khasi mandarin (Citrus
reticulata Blanco). Agri Journal World, 2 (7): 1-7.
Sanchez-Bravo P, Noguera-Artiaga L, Martínez-Tomé J, Hernández F, Sendra
E. 2022. Effect of Organic and Conventional Production on the Quality
of Lemon “Fino 49”. Agronomy, 12(5): 980. https: //doi.org/10.3390/
agronomy12050980
Serna-Escolano, V., Martínez-Romero, D., Giménez, M. J., Serrano, M., García-
Martínez, S., Valero, D. and Zapata, P. J. 2021. Enhancing antioxidant
systems by preharvest treatments with methyl jasmonate and salicylic acid
leads to maintain lemon quality during cold storage. Food Chemistry, 338:
128044.
Shree, R. 2022. How to Cultivate Citrus? [Organically] Agriculture. https:
//www.agricultureinindia.net/cultivation/citrus-cultivation/how-to-
cultivate-citrus-organically-agriculture/18507. Accessed o 23.12.2022
Organic Culture of Tropical and Subtropical Fruit Plants
176 |
Soule J and Grierson W. 1986. Maturity and grade standards. In: Fresh Citrus
Fruit 1st ed. Wardowsky WF, Nagy S and Grierson W (editors.). Westport,
Connecticut, USA: AVI Publishing Co., Inc.; 1986: 23-47.
Tiwari S. 2006. Mandarin: Postharvest management guide. Extension Bulletin,
College of Horticulture and Forestry, Pasighat, India.
Torres J, Valera DL, Belmonte LJ, Herrero-Sanchez C. 2016. Economic and Social
Sustainability through Organic Agriculture: Study of the Restructuring of
the Citrus Sector in the “Bajo Andarax” District (Spain). Sustainability, 8(9):
918. https: //doi.org/10.3390/su8090918
Trinchera A, Tittarelli F, Intrigliolo F. 2007. Study of organic matter evolution
in citrus compost by isoelectro focusing technique. Compost Sci Util., 15(2):
101–110.
USDA Citrus update 2011. Citrus: World markets and trade. http: //www.fas.
usda.gov/htp/2011_July_Citrus.pdf
Vishwa Mohan. 2017. Growth in organic farming sector is mired by fraudulence
and malpractices, says ICRIER report. https: //timesondia.indiatimes.
com/ india/growth-in-organic-farming-sector-is-mired-by-fraudulence-
and-malpractices-says-icrier-report/articleshow/60195356.cms
Vossen, P. and Ingals, C. 2002. Orchard Floor Management. https: //cesonoma.
ucanr.edu/les/27205.pdf
Walsh B. 2013. Internal maturity standards for Citrus fruit. Department of
Agriculture and Food, Australia. Available in: https: //www.agric.wa.gov.
au/internal-maturity -standards-citrus-fruit. (Accessed June 18, 2014).
Wardowski WF, Soule W, Grierson W and Westbrook GF. 1979. Florida citrus
quality tests. Florida Cooperative Extension Service Circular; 1979: 372.
Watson CA, Bengtsson H, Ebbesvik M, Løes A-K, Myrbeck A, Salomon E,
Schroder J, Stockdale EA. 2002b. A review of farm-scale nutrient budgets for
organic farms as a tool for management of soil fertility. Soil Use Manag18:
264–273. https: //doi.org/10.1079/SUM2002127
Willer H, Kilcher L (eds) 2009. The world of organic agriculture: statistics and
emerging trends 2009. IFOAM/FiBL, Bonn/Frick.
Organic Culture of
Tropical and
SubTropical FruiT planTS
– Editors –
Dr. S.N. Ghosh
Professor, Department of Fruit Science (Retired) &
Ex-Dean, Faculty of Horticulture,
Bidhan Chandra Krishi Viswavidyalaya
P.O. Krishi Viswavidyalaya,
Mohanpur, Nadia - 741252, West Bengal, India
Dr. Hare Krishna
Principal Scientist (Horticulture)
ICAR-Indian Institute of Vegetable Research
Varanasi - 221305, Uttar Pradesh, India.
Dr. Heiplanmi Rymbai
Senior Scientist (Pomology),
ICAR Research Complex for NEH Region,
Umiam - 793103, Ri Bhoi, Meghalaya, India
2024
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