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Elsevier Editorial System(tm) for Agricultural Water Management
Manuscript Draft
Manuscript Number: AGWAT7407
Title: Irrigation and nitrogen effects on tuber yield and water use efficiency of heritage and modern
potato cultivars
Article Type: SI: WATER IRRI
Keywords: Irrigation, nitrogen, heritage potato, rain-fed, water use efficiency, economic water
productivity, tuber yield
Corresponding Author: Dr. Isaac Rhinnexious Fandika, PhD
Corresponding Author's Institution: Malawi Government
First Author: ISAAC R FANDIKA, PhD
Order of Authors: ISAAC R FANDIKA, PhD; PETER D KEMP, PhD; JAMES P MILLNER, PhD; DAVIE
HORNE, PhD
Abstract: There is renewed interest in heritage potatoes in New Zealand, USA and Europe because of
their natural flavour and the premiums farmers receive in niche markets. However, a dearth of
information on irrigation and nitrogen limit their successful management. This research investigated
irrigation and N effects on yield and water use efficiency of heritage and modern potatoes. The
2009/2010 experiment was a RCBD split-plot and the 2010/2011 was a RIBD Split-Split-Plot with
water regimes as the main treatments, four cultivars as sub-treatments and two N levels, as sub-sub-
treatments. The N treatment in 2010/2011 was 20 and 180 kg N ha-1 of urea at top dressing. Both
experiments were basal dressed with 500 kgha-1 of 12N: 5.2P:14K6:S+2Mg:Ca at planting. The
2009/2010 was top dressed with 100 kgN ha-1. Data collected was subjected to ANOVA, using the
PROC GLM procedure in SAS. Modern potatoes (Moonlight, Agria) were more responsive to irrigation
and N than heritage potatoes (Moe Moe, Tutaekuri). Moe Moe produced as much marketable yield as
modern cultivars while Tuteukui had low yields. Application of more than 80 kg N ha-1 decreased yield
in heritage potatoes whereas, it increased the yield of modern potatoes. Full irrigation and 80 kg N ha-
1 improved Moe Moe yields whereas partial irrigation and less than 80 kg N ha-1 improved Tutaekuri
yields. Water use efficiency was high in modern potatoes whereas economic water productivity was
high in heritage potatoes. Heritage potatoes tolerated water deficit although they required more water
due to late maturity. It was concluded that premium market prices are important to the success of
heritage potatoes whereas modern potatoes might use irrigation water more efficiently. It is evident
that heritage potatoes can be grown successfully, and that on occasions they use valuable resources
efficiently; however a price premium is required to maintain viability.
Suggested Reviewers: Dave Kadyampakeni PhD, MSc, BSC
Scientist, IWMI, IWMI
dakadyampakeni@gmail.com
Profession in Irrigation water Management
Patson Naliva PHD, MSc, BSC/Diploma
Lecturer, Soil Science, LUANAR
patienalivata@yahoo.com
Profession in nutrient management
Shamie Zingore PhD
Scientists, Soil Science, IPNI
s.zingore@inpi.net
Profession in soil and water
Opposed Reviewers: Patson Nalivata PhD
Lecturer, Crop Science, University of Malawi
patienalivata@yahoo.com
Professional in soil and crop production/management.
DAVIe KADYAMPAKENi PhD
Scientist, IWMI, IWMI
dakadyampakeni@gmail.com
Professional
Patson Nalivata PhD
Lecturer, Soil Science, Bunda College of Agriculture
patienalivata@yahoo.com
Professional
Shamie Zingore Zingore PhD
Director, IPNI, IPNI
s.zingore@inpi.net
Soil and Water Scientist
Kasinthula Agricultural Research Station,
P.O Box 28, Chikwawa,
MALAWI
23th April, 2015
Dear Sir/Madam,
SUBMISSION OF MANUSCRIPT
I would like to submit a manuscript entitled “Irrigation and
nitrogen effects on tuber yield and water use efficiency of
heritage and modern potato cultivars” for publication with your
journal.
I am a male Malawian aged 47 and have studied up to PhD degree in
Agriculture obtained from Massey University, New Zealand in November,
2012; MSc in Water Management – Advanced Irrigation obtained from
Cranfield University (UK) in 2004 and Bsc/Diploma/Certificate in
Agriculture from University of Malawi/Natural Resources College obtained
in 2002 and 1994, respectively. I have over 12 years experience in
Management and Administration – working as Research Station Manager and
20 years experience in Research & Development – working as Chief
Agricultural Research Scientist.
Yours faithfully.
Isaac Rhinnexious Fandika, PhD
Cover Letter
Modern potatoes were more responsive to irrigation and N than heritage potatoes.
80kgN ha-1 decrease yield in heritage potato whilst increasing modern potato yield.
Partial irrigation and 80 kg N ha-1 improved yields in heritage potatoes.
Physical WUE is high in modern potatoes but economically high in heritage potatoes.
Heritage potato tolerates water stress and require more water due to late maturity.
*Highlights (for review)
2
Title: Irrigation and nitrogen effects on tuber yield and water use efficiency of heritage and 1
modern potato cultivars 2
Isaac R. Fandika1, 2, Peter D. Kemp1, James P. Millner1, David Horne1 and Nick Roskruge1 3
1Institute of Natural Resources, Massey University, Private Bag 11222, Palmerston North 4410, 4
New Zealand. Email: fandikai@yahoo.co.uk 5
2Kasinthula Agricultural Research Station, Department of Agricultural Research Services, 6
Ministry of Agriculture & Food Security, P.O Box 28, Chikwawa, Malawi. 7
Email: fandikai@yahoo.co.uk; +265 999336212; +265882925512 8
9
Corresponding Author: Isaac R. Fandika1, fandikai@yahoo.co.uk; +265 999336212; 10
+265882925512 11
12
Abstract 13
There is renewed interest in heritage potatoes in New Zealand, USA and Europe because of 14
their natural flavour and the premiums farmers receive in niche markets. However, a dearth 15
of information on irrigation and nitrogen limit their successful management. This research 16
investigated irrigation and N effects on yield and water use efficiency of heritage and modern 17
potatoes. The 2009/2010 experiment was a RCBD split-plot and the 2010/2011 was a RIBD 18
Split-Split-Plot with water regimes as the main treatments, four cultivars as sub-treatments 19
and two N levels, as sub-sub-treatments. The N treatment in 2010/2011 was 20 and 180 kg N 20
ha-1 of urea at top dressing. Both experiments were basal dressed with 500 kgha-1 of 12N: 21
5.2P:14K6:S+2Mg:Ca at planting. The 2009/2010 was top dressed with 100 kgN ha-1. Data 22
collected was subjected to ANOVA, using the PROC GLM procedure in SAS. Modern 23
*Manuscript
Click here to download Manuscript: Fandika - 2015.docx Click here to view linked References
3
potatoes (Moonlight, Agria) were more responsive to irrigation and N than heritage potatoes 24
(Moe Moe, Tutaekuri). Moe Moe produced as much marketable yield as modern cultivars 25
while Tuteukui had low yields. Application of more than 80 kg N ha-1 decreased yield in 26
heritage potatoes whereas, it increased the yield of modern potatoes. Full irrigation and 80 27
kg N ha-1 improved Moe Moe yields whereas partial irrigation and less than 80 kg N ha-1 28
improved Tutaekuri yields. Water use efficiency was high in modern potatoes whereas 29
economic water productivity was high in heritage potatoes. Heritage potatoes tolerated water 30
deficit although they required more water due to late maturity. It was concluded that 31
premium market prices are important to the success of heritage potatoes whereas modern 32
potatoes might use irrigation water more efficiently. It is evident that heritage potatoes can 33
be grown successfully, and that on occasions they use valuable resources efficiently; however 34
a price premium is required to maintain viability. 35
36
Keywords: Irrigation, nitrogen, heritage potato, rain-fed, water use efficiency, economic 37
water productivity, tuber yield 38
Introduction 39
Heritage potatoes (Solanum tuberosum) refer to speciality potato cultivars or very old 40
Southern America native potato cultivars that Europeans originally transported or smuggled 41
to Europe and other parts of the world, traditionally produced without a patent (Voss et al., 42
1999). Generally, heritage potatoes are cultivated by small farmers and have a diversity of 43
yield potential, tuber size and multi-colour skin/flesh (yellow-flesh, purple skin, red flesh) 44
(Harris 2001; Voss et al., 1999). Consumer demand for such multi-coloured potatoes is high 45
in the USA, South America (Voss et al., 1999), New Zealand (Hayward, 2002; McFarlane, 46
2007) and Europe niche markets, due to their natural flavour (Walker, 1996), texture or 47
4
colour and health benefits (Singh et al., 2008; Lister 2001). They also have good nutritional 48
traits and ‘novel’ value. Premium prices are offered for heritage potatoes in New Zealand 49
(Hayward, 2002; McFarlane 2007) and USA (Voss et al., 1999) because of novelty value as 50
well as for their cultural value (Lambert, 2008; McFarlane, 2007). Consequently, there is an 51
interest in producing heritage potatoes to supply those niche markets. 52
California is the largest producer and market for speciality potatoes in USA (Voss et al., 53
1999). In New Zealand, the indigenous Polynesian population (Maori) traditionally produce 54
these potatoes, collectively known as Taewa (Roskruge, 1999). Heritage potatoes have other 55
increased advantages including biodiversity and most of them are self – selected, hence have 56
potential to withstand biotic and abiotic stresses (Roskruge, 2010). However, speciality or 57
heritage potatoes growers in USA (Voss et al., 1999), Europe and New Zealand experience 58
low yields (Harris 2001; Harris et al., 1999). Heritage potatoes generally respond less to 59
inputs such as irrigation and N input compared with modern cultivars (Fandika et al., 2010; 60
Hayward, 2002). Most heritage cultivars are produced without appropriate water and soil 61
management as also observed in burley (Abeledo et al., 2011). Growers of heritage cultivars 62
need to be able to use water and N resources prudently by selecting suitable cultivars, in order 63
to maximise yields and returns. This research compares tuber yield, water and nitrogen use 64
efficiency of heritage and modern potato cultivars in response to irrigation and nitrogen 65
fertiliser management. 66
Materials and Methods 67
Location and experimental design 68
Two heritage potatoes, Moe Moe (S. tuberosum L.) and Tutaekuri (Solanum andigena Juz. & 69
Buk.) and two modern cultivars, Moonlight and Agria (S. tuberosum L.) were compared in the 70
field at the Pasture and Crop Research Unit, Massey University, Palmerston North from 10th 71
5
November, 2009 to May, 2010 and from 27th October, 2010 to April, 2011. The site is located 72
at a latitude of 40o 22. 54.02 S, longitude 175 o 36’ 22.80 E, and an altitude of 36 m above 73
sea-level. The soil type is Manawatu sandy loam, a recent alluvial soil. The soil samples were 74
analysed at Massey University’s Fertilizer and Lime Research Centre. The soil properties 75
were: pH 5.4, Olsen P 36 mg kg-1 and K 86.02 mg kg-1. The soil bulk density was 1.35 g cm-3 76
and the volumetric soil water content, at field capacity and wilting point, were 0.35 and 0.17 m3 77
m-3, respectively. There were 106 kg ha-1 of available N and 76.8 mg N kg-1 of soil 78
anaerobically mineralised N at the beginning of the 2009 - 2010 experiment. In 2010 - 2011, 79
total available N was <30 kg N ha-1. Figure 1 presents the maximum and minimum 80
temperature, evapotranspiration and rainfall (mm) for the site during the experiment. 81
82
The 2009-2010 experiment was a randomised complete block split-plot design, with rain-fed 83
and full irrigation (as the main treatments) with four potato cultivars as sub-treatments. This 84
crop received 12N:5.2P:14K:6S+2Mg+5Ca, using 500 kg Nitrophoska Blue TE at planting 85
on 10th November, 2009 and this was followed by 100 kg N ha-1 of urea, as a side dressing, 86
on 15thDecember, 2009. Potato tubers were manually sown at 75 cm spacing between rows 87
and 40 cm spacing within rows at a depth of 10 - 15 cm. Each plot was 6 m by 1.5 m and 88
each plot held 30 plants. Each plot had two guard rows planted with the Desiree variety. The 89
2010/2011 experiment was a Randomised Incomplete Block Split-Split-Plot Design with 90
rain-fed (Pe); (2) partial irrigation (PI) and (3) full irrigation (FI) (as the main treatments): 91
three potato cultivars (Agria, Moe Moe and Tutaekuri) as sub-treatments and two N levels 92
(N1=80; N2=240 kg N ha-1), as sub-sub-treatments. Both experiments were replicated four 93
times. All plots received the same amount of fertiliser as in 2009/2010 at planting but N1 and 94
N2 treatments were side dressed by 20 and 180 kg N ha-1 on 10th December, 2010. Spacing 95
within plants was 30 cm and other parameters were as 2009/2010 above. 96
6
Irrigation scheduling and soil moisture measurements 97
Irrigation was applied with a Trail T150-2 traveller irrigator. A soil water balance was used to 98
determine the soil moisture deficit (SMD) on a daily basis during the growth of the crops 99
(Premrov et al., 2010). The potential evapotranspiration in the soil water balance was 100
computed using the FAO 56 Penman-Monteith method (Allen et al., 1998; Kassam et al., 101
2001). The daily weather data, for running the soil water balance model, were collected 102
weekly from NIWA/AgResearch climate site, Palmerston North. The soil water balance was 103
used to schedule irrigation events and to calculate the quantity of drainage (Dp) over the 104
growing period. The full irrigation treatment was based on refilling 25 mm of the soil’s 105
moisture deficit (SMD) on the day that soil moisture deficit equated to or exceeded 30 mm. 106
This schedule was based on supplying approximately half the ‘readily available water’ held 107
by the soil at the site. Partial irrigation treatment did not receive irrigation at the first 108
irrigation of the full irrigation treatment and was then irrigated at every second full irrigation. 109
The actual water distribution within each plot was monitored (at every irrigation) by using a 110
number of catch cans. The catch cans were laid longitudinally at 0.5 m apart. At the end of 111
the irrigation period, water trapped in the cans was measured and recorded. The irrigation 112
depth for a particular plot was determined as an average of the water depth in the six catch 113
cans from each plot. 114
115
The actual crop evapotranspiration (ETc) was determined using equation 1 (Allen et al., 116
1998). Soil moisture change (∆S) was the difference between soil moisture content at the end 117
and the start of the field experiment as measured using a Time-Domain Reflectometer, 118
model 1502C, Tektronix Inc., Beaverton, OR, USA. In addition to measuring soil water 119
content at the start and conclusion of the trial, it was also monitored before irrigation and 24 120
7
hours after irrigation to a depth of 50 cm. As the site was flat and the crops were in the 121
ground for the summer/autumn period, surface runoff can be ignored. 122
123
ETc = P + I - Dp - Ro+ ∆S Equation 1 124
125
Tuber yield components, Nitrogen use efficiency and water use efficiency 126
After physiological maturity, the crop was harvested using a potato harvester. Total tuber 127
yield (kg); marketable tuber yield; number of tubers per plant; average tuber weight, 128
aboveground (leaves+stems) and total biomass (leaves+stems+tuber) were measured. The 129
harvest index (HI) was calculated as the ratio of total tuber yield to total biomass production 130
on dry weight basis, in five samples from each plot (Mackerron & Heilbronn, 1985). Tubers 131
were later graded into marketable and non-marketable grades (NM): a marketable tuber was 132
above 55g without any defects and a non-marketable tuber was <55g and those with defects. 133
Water use efficiency (WUE) was defined as fresh matter production per unit water applied as 134
rainfall, plus irrigation, plus change in soil moisture content (Howell, 2001). Nitrogen use 135
efficiency (NUE) was determined as the total tuber yield, per unit of N applied per treatment 136
(kg N kg-1) (Darwish et al., 2006; Zebarth et al., 2008). 137
Statistical Analysis 138
Tuber yield and components data was analysed with the General Linear Model (GLM) 139
procedure of the Statistical Analysis System (SAS, 2008). Differences amongst treatment 140
means were compared by the Least Significant Difference test (LSD), at 5% probability 141
(Meier, 2006). A simple correlation analysis was used to assess the relationship between the 142
daily crop water use and solar radiation, maximum temperatures and wind from November to 143
April. A simple correlation was also used to assess the relationship between number of tubers 144
per plant to the average tuber weight and HI. 145
8
Results 146
147
Crop water use and volumetric soil moisture content 148
Heritage potato cultivars matured 179 and 170 days after planting whereas modern potatoes 149
took 132 and 140 days to mature in 2009/2010 and 2010/2011, respectively. Heritage 150
potatoes potentially required 610 mm and 611 mm whilst modern potatoes required 550 and 151
491 mm in the respective years (Figure 1). Precipitation supplied 60 - 69% of the water 152
requirement. Consumptive water use (m3 ha-1) was highest in the FI and lowest in the Pe 153
treatment, whilst PI was intermediate. Heritage potatoes used more water compared to the 154
modern cultivars in both experiments. Since precipitation was not well distributed during the 155
growing seasons, irrigation reduced the soil moisture deficit in all cultivars. 156
157
Volumetric soil moisture content (%) in the Pe treatments ranged between 15 - 20%, whilst 158
irrigated treatments ranged between 20 - 35% (Figure 2). Full irrigation increased soil 159
moisture content, whereas N had no effect on soil moisture content in 2010 - 2011 (P>0.05). 160
The daily crop water use (in both years) was strongly influenced by solar radiation (P<0.0001) 161
and maximum temperatures (P<0.0001), but was not influenced by. The high temperature and 162
solar radiation experienced in January and February caused the maximum ETc. 163
164
9
Tuber yield and components 165
Irrigation significantly increased average tuber weight (P<0.001), total tuber yield (P<0.0001) 166
and marketable tuber yield in 2009 - 2010 (P<0.01; Table 1). The average number of tubers 167
per plant and HI were not influenced by irrigation. However, cultivar strongly influenced the 168
number of tubers per plant, average tuber weight (P<0.0001), total and marketable tuber yield 169
(P<0.0001) and HI (P<0.0001) in 2009 - 2010 (Table1). In 2010 - 2011, tuber yield and all 170
yield components above were influenced by cultivar (P<0.0001), irrigation (P<0.001) and N 171
(P<0.0001; Table 1). 172
173
Modern cultivars had the lowest number of tubers per plant, Tutaekuri the highest whilst Moe 174
Moe was intermediate. The greatest average tuber weight was found in Agria, the least in 175
Tutaekuri. Modern cultivars had higher HI, total and marketable tuber yield than heritage 176
potatoes, except in 2009/2010 when Moe Moe produced as much yield as modern cultivars. 177
Moe Moe and Agria had more tubers under rain-fed conditions in 2009/2010. Modern 178
cultivars did not differ in the number of tubers per plant and average tuber weight traits, 179
whilst heritage potatoes differed from each other (P<0.0001; Table 1). The behaviour of 180
translocating assimilates to the harvested product was clearly demonstrated by the high HI in 181
Agria. Tutaekuri had the lowest HI whilst Moe Moe was intermediate. The number of tubers 182
and the average tuber weight were negatively related to average tuber weight (Average tuber 183
weight (g) = - 1.6618 (Tubers plant-1) + 110.29, R2 = 66.3%) and HI (HI = - 0.0059 (Tubers 184
plant-1) + 0.8902, R2 = 60.5%) in 2009/2010. The increase in the number of tubers per plant 185
in heritage potatoes significantly decreased the average tuber weight and HI. 186
187
In 2009/2010, irrigation did not affect the number of tubers per plant in modern cultivars, or 188
the number of tubers, the mean tuber weight and total and marketable tuber yields in 189
10
Tutaekuri (P>0.05). Conversely, the number of tubers per plant in Moe Moe were reduced 190
and there was an increase in the mean tuber weight with irrigation (P<0.001). Subsequently, 191
the total and marketable tuber yields in Agria, Moonlight and Moe Moe did not differ but 192
they were all higher yielding than Tutaekuri, under both irrigation treatments in 2009/2010 193
(P<0.0001). Full irrigation reduced yields in Tutaekuri and PI enhanced yields more than FI 194
and rain-fed treatment in 2010/2011 (Figure 6). Partial irrigation increased tube yield by 195
increasing number of tubers and FI by enhancing mean tuber weight. Nitrogen did not 196
increase the average tuber yield (P<0.05). 197
198
Irrigation enhanced the average tuber weight, fresh total tuber yield and marketable tuber 199
yield, by 51%, 33% and 55% in 2009/2010, respectively. In 2010/2011, FI increased the 200
number of tubers per plant; mean tuber weight; total tuber yield; and marketable tuber yield 201
by 18%, 6%, 43% and 49%, whilst PI enhanced them by 24%, 6%, 26% and 13%, 202
respectively (Table 1). However, high N decreased tuber numbers; total tuber yield and 203
marketable tuber yield by 16%, 17% and 14%, respectively (P<0.0001). On the other hand, N 204
did not enhance average tuber weight (P>0.05). 205
206
There was irrigation and cultivar interaction on tuber yield in 2009/2010 resulting from 207
increased tuber yields in Agria, Moonlight and Moe Moe, but not in Tutaekuri with FI 208
(P<0.01; Figure 3). The effect of water stress was highly pronounced in Agria and Moonlight 209
compared with the heritage cultivars. In 2010 - 2011, significant interactions were observed 210
between cultivars and irrigation on the number of tubers per plant (P<0.0001, Figure 4a) and 211
total and marketable tuber yield (P<0.0001, Figure 6). Cultivar and N significantly interacted 212
on the number of tubers per plant (P<0.01, Figure 4b) and mean tuber weight (P<0.05, Figure 213
5), total and marketable tuber yield (P<0.0001). Significant interactions were also observed 214
11
between cultivar, irrigation and N on total and marketable tuber yield (P<0.01) (Figure 7). No 215
interactions were observed between irrigation and N (P>0.05), apart from HI (P<0.05). 216
217
The interaction involving the tuber numbers per plant was a consequence of decreased tuber 218
with FI and rain-fed, whilst it increased with PI in Tutaekuri. In other cultivars, the number of 219
tubers decreased from FI to rain-fed (Figure 4a). Nitrogen reduced tuber number per plant in 220
heritage cultivars but not in Agria (Figure 4b). The mean tuber weight in Agria increased 221
with N increase, whereas heritage potatoes decreased its mean tuber weight with N increase 222
(Figure 5). Similarly, total and marketable tuber yield in Agria increased with high N but 223
decreased in heritage cultivars (Figure 6). Without irrigation, the response to N was reduced 224
(Figure 7). Tutaekuri performed better under PI compared to FI and rain-fed, whilst the 225
remaining cultivars performed best under FI (Figure 6a). 226
227
Water use efficiency and nitrogen use efficiency 228
Water use efficiency mirrored tuber yield in both years, whereas economic water productivity 229
(EWP in NZ$/m3) reflected the product marketable value, in addition to tuber yield (Table 1 230
& 2). Water use efficiency was highest in Moonlight in 2009/2010 (Table 1) and in Agria in 231
2010/2011 and lowest in Tutaekuri, whereas Moe Moe was intermediate in both years 232
(P<0.0001). Water use efficiency was significantly influenced by water regimes (P<0.001) 233
and N (P<0.0001) in all cultivars, although differently. In 2009/2010, rain-fed treatments had 234
high WUE. Tutaekuri had significicantly lower WUE (P<0.05) than all other cultivars apart 235
from Agria whereas WUE in Moonlight did not differ from Moe Moe under rain-fed 236
conditions. Under irrigated conditions, WUE was higher in Moonlight (Table 1). 237
238
12
In 2010/2011, WUE was highest under PI and low N, whereas FI had the lowest WUE (Table 239
1). Rain-fed treatment was intermediate but not different from either PI or FI. Full irrigation 240
decreased WUE, whilst PI increased it in all cultivars (Figure 8). Water use efficiency 241
decreased with increasing N in Taewa and rain-fed Agria, whereas PI and FI did not affect 242
WUE at high N in Agria (P<0.01, Fig. 8). Economic water productivity was highest in Moe 243
Moe and lowest in Tutaekuri, with Agria intermediate (P<0.0001, Table 2). Partial irrigation 244
and low N increased EWP, whilst FI and high N decreased EWP (P<0.01, P<0.0001). The 245
interaction involving EWP resulted from the increase in EWP at high N and PI in Agria, 246
whereas Taewa had decreased EWP at high N. 247
248
Nitrogen use efficiency was highest in Agria, (P<0.0001), FI (P<0.0001) and low N 249
treatments (P<0.0001; Table 2; Figure 9). Tutaekuri, rain-fed and high N treatments had the 250
lowest NUE. Interaction effects were observed between water regime and cultivars 251
(P<0.0001); water regime and N (P<0.01); cultivars and N (P<0.0001); cultivar and water 252
regime and N on NUE in 2010/2011 (P<0.05). Full irrigation increased NUE in Agria and 253
Moe Moe, whereas PI increased NUE in Tutaekuri. High N decreased NUE by over 300% in 254
heritage cultivars, whereas rain-fed decreased it by 40% (Table 2). Partial irrigation had an 255
intermediate influence on NUE in Moe Moe and Agria (Figure 9). 256
257
Discussion 258
Crop water use and tuber yield 259
The study indicates that irrigation improves potato tuber yields (Erdem et al., 2006) and also 260
that there are potato genotypic differences in water use (Steyn et al., 1998; Trebejo et al., 261
1990; Wolfe et al., 1983). The heritage and modern potatoes differed in their maturity and 262
13
water requirement. The heritage potatoes used more water than modern cultivars when water 263
was available because they mature later. However, heritage potatoes were more adapted to 264
water deficit compared to modern potatoes. The rainfall did not supply enough water to both 265
heritage and modern potatoes to meet their water requirements. Consequently, rain-fed 266
conditions resulted in a greater reduction in tuber yield than partially irrigated potatoes. 267
Growers need to understand the growing stages and related daily water use of their heritage 268
potatoes in order to improve yield and WUE. 269
270
Tuber yield increased linearly with irrigation, depending on genotypes, with the highest 271
increase being found in modern potatoes. Conspicuously, the response to irrigation was high 272
in cultivars that are very sensitive or not tolerant to water stress, predominantly modern 273
cultivars. This is interestingly supported by the high reduction of modern potatoes yields 274
with a mild water stress, as compared to the heritage cultivars. This supports Trebejo, (1990) 275
findings that cultivars which perform well under adequate water may not do well under water 276
stress, unless the cultivar is stable to both a stressed and non-stressed environment, as 277
observed with Moe Moe in 2009 - 2010. 278
279
The yield response to irrigation and N of heritage potatoes was generally lower than the 280
modern potato cultivar. For instance, Moe Moe and Agria tuber yield responded to FI, whilst 281
Tutaekuri responded to PI. Both Tutaekuri and Moe Moe decreased tuber yield with high N, 282
whereas Agria increased tuber yield with high N. The high N reduced tubers per plant, tuber 283
weight and HI in heritage potatoes, whilst increasing them in the modern cultivar. This 284
indicates that, although N improves yields in irrigated potato more than in water-stressed 285
fields (Ferreira et al., 2007), the response to N depends on cultivars, as reported for Agria, 286
Fianna, Russet Burbank, Ilam Hardy and Kennebec cultivars in New Zealand (Craighead et 287
14
al., 2003). Consequently, heritage potatoes growers do not need to apply up to 210 - 250 kg 288
ha-1 of N applied to modern potato cultivars (Craighead et al., 2003). 289
290
Irrigation enhances potato yields through the modification of mean tuber weight and number 291
of tubers per plant differently, depending on the cultivar (Belanger, 2002; Walworth et al., 292
2002). In both years, FI moderately improved the number of tubers, HI and mean tuber 293
weight in Agria and Moe Moe, whilst decreasing them in Tutaekuri. However, the adjustment 294
in Moe Moe in 2009 - 2010 was accompanied by a modification of the number of tubers per 295
plant be fewer than under rain-fed. The increase in mean tuber weight confirms other findings 296
by Bélanger et al.(2002), Ferreira et..al. (2007) and Yuan et al. (2003), while the decrease in 297
number of tubers with irrigation in Moe Moe is contrary to Belanger et..al. (2002) and Yuan 298
et..al. (2003), who reported an increase of tuber numbers per plant with irrigation as also 299
observed in 2010 - 2011. 300
301
In 2009 – 2010, Moe Moe (a heritage cultivar) had competitively produced equally to modern 302
cultivars, due to an intermediate number of tubers and mean tuber weight. Moe Moe yield 303
was more than the average potato yield of 45.3 - 50.2 t ha-1 in New Zealand (FAO, 2009; 304
McKenzie, 1999). It was also above world potato average yields, which range from 10.8 to 305
41.2 t ha-1 (FAO, 2009a). This result is also within the average potato tuber yield range of 38 306
- 55.4 t ha-1, upon which most modern potatoes are accepted for release (Anderson et al., 307
2004; Genet et al., 1997; Genet et al., 2001). The performance of Moe Moe dispeled claims 308
which generalise that heritage potatoes are 50% poorer in their yields (Harris et al., 1999) and 309
it indicated the possibility of achieving high yields in heritage potatoes heritage potatoes with 310
correct water management. 311
312
15
Full irrigation and high N terrifically failed to improve the tuber yield in one heritage cultivar, 313
Tutaekuri, possibly due to differences in their sub-species and HI. Tutaekuri is sub-specie 314
andigena, whilst others are sub-specie tuberosum. Tutaekuri behaviour in response to 315
irrigation and N confirms that modern cultivars are bred for high N responsiveness while old 316
or wild cultivars have low N use because they were self-selected for adverse condition 317
(Zebarth et al., 2008; Siddique et al., 1990a). However, S. andigena, (Tutaekuri) yield 318
potential appears to be lower than the average of S. tuberosum (Moe Moe) yields. Kumar et 319
al. (2006) described S.andigena yields to be primitive and limited by large above-ground 320
biomass, large tuber numbers per plant and small tuber size. The tuber yield gap between the 321
two heritage potatoes is very wide and difficult to close through agronomic practices because 322
it is dependent on genotypic variation. Nevertheless, the study indicates the possibility of 323
achieving higher tuber yields in S.andigena (Tutaekuri), with partial irrigation and low N. 324
The tuber yields for both heritage potatoes varied with season and N levels. The main driver 325
of change in the average tuber yields between the seasons was the potato psyllid infestation in 326
2010 - 2011. Compared with 2009 - 2010, heritage potatoes production in 2010 - 2011 327
decreased, with an average tuber yield of 18.1 t ha-1 in Moe Moe and 10.9 t ha-1 in Tutaekuri. 328
This result shows that one of the main limitations to heritage potatoes is potato psyllid 329
infestation, apart from low yield potential, inappropriate N and water management. Pest 330
control is essential in heritage potatoes, despite their hardiness and tolerance to some biotic 331
and abiotic stresses, which have been developed through their self-selection (Roskruge et al., 332
2010). Therefore, heritage potato growers are advised to strategise pest and disease 333
management, in order to attain maximum yields and to avoid tuber yield decrease between 334
seasons. 335
336
16
Visual surveillance showed potato psyllid symptoms 110 - 150 days after planting (Table 2; 337
Fig. 10). The attack had less impact on Agria yield, since it had already developed tubers, 338
whilst heritage potatoes were still developing tubers when infested: hence, heritage potatoes 339
yields were probably decreased due to the pest’s disruption of the photosynthesis and tuber 340
dry matter accumulation process. This study is illustrative of the claim that the low tuber 341
yields commonly reported for heritage potatoes may be at least partly due to pests, low HI 342
and inefficient water management. However, these tuber yields are considerably above the 343
current mean total and marketable tuber yields attained by heritage potato growers, ranging 344
from 15 - 20 t ha-1 and 10 - 15 t ha-1, respectively (Roskruge, 2011 pers. comm.). Appropriate 345
irrigation and N application contributes to improvement in the tuber yield of heritage potatoes. 346
Full irrigation and PI combined with less than 80kg N ha-1, respectively, raised Moe Moe and 347
Tutaekuri tuber yields towards a potential yield of 40 t ha-1. 348
349
Water use efficiency and Nitrogen use efficiency 350
Amongst the world’s major food crops, potato has been reported to have a high WUE of 6.2 - 351
11.6 kg m-3, compared to cereal and legume grain crops (Bowen, 2003; FAO, 2008; 352
Thompson et al., 2003; Zhang et al., 2005). The WUE for modern potato and Moe Moe are 353
within this range. The WUE for potato has been reported above 11.6 kg m-3, as also observed 354
with some modern potato in this study (Kang et al., 2004; Trebejo et al., 1990). Erdem et al. 355
(2006) reported WUE for potatoes below 6.2 kg m-3, as observed in Tutaekuri. The reason for 356
low WUE in Tutaekuri could be its genetics on small tuber size or higher tuber number and 357
higher vegetative growth than tuber yield. The WUE for Tutaekuri would improve with the 358
enhancement of HI as reported in grain WUE (Siddique et al., 1990). Nevertheless, the WUE 359
for Tutaekuri is above WUE for the major crops of the world and therefore, may be a 360
valuable crop when water is limited. 361
17
362
Modern potatoes have high physical WUE, but they are not as economically productive under 363
the same volume of water as heritage potatoes. Similarly, the irrigation scheduling 364
technology, for improving WUE in Agria, is different for Tutaekuri. The results on EWP 365
confirm the findings of Nielsen et al. (2005) that WUE, based on a dollar return per unit of 366
water used, is sometimes high in those crops found with low evaporative demand, rather than 367
those crops with a high evaporative demand (Nielsen et al., 2005; Nielsen et al., 2006 ). 368
Likewise, market values or high values have determinature effect on water productivity. 369
Aldaya et al. (2008) reported that the use of water for low value crops is sometimes the main 370
problem, rather than water scarcity. Vegetables with high value were more economically 371
productive, per volume of water (15 Euro/m3 ≈ 27 NZ$/m3), than grain cereal with less value 372
(0.3 Euro/m3 in Spain (Aldaya et al., 2008). In this study, heritage potatoes demonstrated 373
higher cash per volume of water used than modern potatoes with their high yield per unit of 374
water. These results, together with those reported from other authors; suggest that the market 375
value of a product should be one of the driving forces in the allocation of water in agriculture. 376
Nitrogen use efficiency was found to be highest under unlimited irrigation and limited N, but 377
the consequence is that WUE is reduced. On the other hand, NUE was found to greatly differ 378
between modern potato and Taewa. This finding is similar to Zebarth et al. (2008) who found 379
that commercial potato cultivars have a higher or equal NUE, compared to Andean primitive 380
cultivars. However, this study does not agree with Zerbarth’s earlier study (Zebarth et al., 381
2004), which indicated that late maturity increases NUE: heritage potatoes, although late 382
maturing, had a low NUE compared to the short duration cultivar, Agria. 383
In another similar study, Errebhi et al. (1999) assessed NUE in tuber bearing solanum species 384
(wild Species and their hybrids) and commercial cultivars, at low and high N. It was found 385
that NUE was highest in wild species, with a minimal difference from Russet Burbank, but it 386
18
was greater than that found in other modern potato cultivars (Errebhi et al., 1999). Heritage 387
potatoes, especially Tutaekuri, has low NUE and WUE, due to their self-selection for survival 388
to adverse competition and environmental factors, whilst modern or commercial potato 389
cultivars are either bred for high NUE or WUE (Zebarth et al., 2008). However, the 390
comparison of heritage potatoes NUE with wild species (Errebhi et al., 1999) suggest that 391
NUE also varies between unimproved potato species (heritage or wild specises) with others 392
exhibiting high NUE whilst others low NUE. Partial irrigation and low N are significant 393
resource saving strategies for heritage potatoes, through the lowering of actual ET below full 394
water supply, whilst keeping tuber yield that approached the tuber yield of modern potatoes. 395
Therefore, the use of high WUE potato cultivars, moderate N and appropriate irrigation 396
scheduling, facilitates the maximisation of crop water productivity (Wallace, 2000; Morison et 397
al., 2007). 398
Conclusion 399
400
Modern potatoes are more responsive to irrigation and N application than heritage potatoes. 401
Some heritage potatoes can produce as much marketable yield as modern cultivars while 402
other heritage potatoes have lower yields than modern heritage. The heritage potatoes use 403
more water (when available), due to late maturity, and are also tolerant to water and N deficit 404
in time of scarcity, unlike modern potatoes. As a result, irrigation and N are important for 405
both heritage and the modern potatoes — although in different ways. The higher number of 406
tubers and the disparity in water and N agronomic practices contribute to the low yield and 407
WUE commonly observed in heritage potatoes. Full irrigation and high N are recommended 408
for modern potatoes; FI and 80 kg N ha-1 are recommended for Moe Moe whereas PI and less 409
than 80 kg N ha-1 are recommended for Tutaekuri production. 410
19
Modern cultivars have higher WUE and NUE than some heritage potatoes. Moe Moe, a 411
heritage cultivar has comparable yield and physical WUE capability to modern cultivars. The 412
heritage cultivars’ WUE is high when assessed in economic terms. The low HI, the higher 413
number of tubers and the disparity in appropriate agronomic practices (pest control) 414
contribute to the low yield and physical WUE commonly observed in heritage crops. In this 415
case, it can be concluded that most heritage crops have a potential for maximising yield with 416
proper irrigation and N strategies. It is evident that heritage crops can be grown successfully, 417
and that on occasions they use valuable resources efficiently. To enhance water use efficiency, 418
management of heritage heritage potatoes should focus on improving the harvest index. 419
Acknowledgement 420
We are indebted to New Zealand’s International Aid and Development agency and the 421
Malawi Government for providing Mr Fandika with a Commonwealth Scholarship, in order 422
to pursue PhD programme. We are also grateful to the Institute of Natural Resources, Massey 423
University, New Zealand for partly funding this research. Lastly, we would like to thank all 424
the technical support from Mark Osborne and Esther Fandika for providing support with 425
other field work during this study. 426
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557
TABLES
Table 1 Yield and yield components for Taewa and modern potato cultivars under irrigation and
rain-fed conditions in 2009 – 2010 and 2010 - 2011
Water Regime/
Cultivars
Tubers
Plant-1
Mean
Tuber
Weight
(g)
Total
Tuber
Yield
(t ha-1)
Marketable
Tuber
Yield
(t ha-1)
Harvest
Index
(HI)
WUE
(kg ha-1 m3)
2009- 2010
Irrigation
Agria
15.7c
112.1a
51.7a
38.5a
0.88a
10.3ab
Moonlight
18.4c
97.1a
59.4a
45.9a
0.78a
11.8a
Moe Moe
25.9b
61.1b
52.6a
45.4a
0.70b
9.4b
Tutaekuri
60.5a
13.7c
27.6b
13.6b
0.50c
5.2c
Mean (n=16)
30.1
71.0
47.8
35.9
0.72
9.2
Rain-fed
Agria
17.1c
64.3a
34.4a
27.2a
0.78a
10.9ab
Moonlight
17.4c
69.9a
39.7a
27.6a
0.78a
12.9a
Moe Moe
31.5b
38.9b
40.1a
24.1a
0.67b
12.1a
Tutaekuri
60.4a
15.1c
30.0b
13.8b
0.56c
9.0b
Mean (n=16)
31.6
47.1
36.1
23.2
0.70
11.2
Significance
Cultivars
P<0.0001
P<0.0001
P<0.0001
P<0.0001
P<0.0001
P<0.05
Water regime
Ns
P<0.001
P<0.0001
P<0.001
Ns
P<0.01
Interaction
Cultivars
Ns
Ns
P<0.001
Ns
Ns
Ns
2010 - 2011
Cultivar
Agria
14.9b
70.01a
45.7a
38.9a
0.80
12.4a
Moe Moe
15.9b
39.4b
27.8b
22.2b
0.48
6.1b
Tutaekuri
28.1a
16.2c
20.1c
14.7c
0.47
4.5c
Significance
P<0.0001
P<0.0001
P<0.0001
P<0.0001
P<0.0001
P<0.0001
Water regime
FI
20.3a
45.2a
36.3a
29.7a
61.5
7.0b
PI
21.4a
41.4ab
32.0b
26.1b
60.1
8.0a
Rain-fed
17.2b
39.1b
25.3c
20.0c
54.2
7.9a
Significance
P<0.05
P<0.0001
P<0.0001
P<0.001
P<0.001
Nitrogen levels
80
21.3a
47.8
34.1a
27.2a
62.4
8.3a
240
17.9b
41.0
28.3b
23.3b
54.8
7.0b
Significance
Ns
P<0.0001
P<0.0001
P<0.0001
P<0.0001
cv.(%)
16.3
20.4
11.5
14.1
10.6
-
Interactions
Cultivar*WR
P<0.0001
Ns
P<0.0001
P<0.0001
P<0.01
P<0.01
Cultivar*N
P<0.01
P<0.05
P<0.0001
P<0.0001
P<0.001
P<0.0001
WR*N
Ns
Ns
Ns
Ns
P<0.05
Ns
Tables
Click here to download Tables: TABLES.docx
WR*Cultivar.*N
Ns
Ns
P<0.01
P<0.01
P<0.01
P<0.01
Note: FI refers to full irrigation whereas PI is partial irrigation, WR is water regime, N is
nitrogen. The columns with the same letters within the water regime treatments are not
statistically different (LSD0.05).
Table 2 Potato psyllid scores, nitrogen use efficiency (NUE) and economic water productivity
(EWP) (NZ$/m3) for Taewa and modern potato cultivars under different water and
nitrogen regimes, 2010/2011
Water regime
/Cultivar
Potato
Psyllid
NUE
(Kg kgN-1)
Economic water
Productivity
(NZ$/m3)
110 DAP
140 DAP
Potato cultivars (n=24)
Agria
2.8a
3.4a
373.2a
14.96b
Moe Moe
0.54b
3.3a
257.7b
19.32a
Tutaekuri
0.31b
2.8b
184.9c
12.98c
Significance P<0.0001
P<0.05
P<0.0001
P<0.0001
Water regimes (n=24)
FI
1.2
3.7a
313.5a
14.6b
PI
1.1
3.0b
277.6b
17.0a
Rain-fed
1.2
2.7b
224.8c
15.7ba
Significance
Ns
P<0.05
P<0.0001
P<0.01
Nitrogen (n=36)
80
1.1
2.6b
425.9a
18.0a
240
1.3
3.6a
118.0b
13.6b
Significance
Ns
P<0.0001
P<0.0001
P<0.0001
Interactions
Water regime*Cultivar
Ns
P<0.001
P<0.0001
P<0.001
Cultivar*N
Ns
P<0.05
P<0.0001
P<0.0001
Water regime*N
Ns
Ns
P<0.01
Ns
Water regime*Cult.*N
Ns
Ns
P<0.05
Ns
1
FIGURES
(a) = 2009/2010
(b) = 2010/2011
Figure 1 Cumulative rainfall (mm), cumulative crop evapotranspiration (mm), monthly
average maximum and minimum temperatures (Co) for the experimental site
during the experiment period from November 2009 to June 2010
Figure
2
Figure 2(a) Volumetric soil moisture (%)
change in Taewa and modern potato
under irrigation and rain-fed
conditions in 2009/2010. Error bar
represents ±SEM.
Figure 3(b) Change in volumetric soil
moisture content (%) for water
regime overtime in 2010/2011.
3
Figure 3 Interaction between cultivars and water regime on total tuber yield (t ha-1) in
2009/2010. Error bar represents ±SEM.
4
Figure 4 (a) Interaction between water regime*cultivar; (b) interaction between cultivar *
nitrogen, on number of tubers per plant: Error bar represents ±SEM.
5
Figure 5 Interaction between nitrogen and potato on mean tuber weight (g). Error bar
represents ±SEM.
Figure 6 Interaction between water regime
and potato cultivars. (Error bar
represents ±SEM.
Figure 7 Interaction between cultivars,
irrigation and nitrogen regime on total
tuber yield (t ha-1). Error bar represents
±SEM.
6
Figure 8 Interaction between cultivars,
irrigation and N regime on WUE
(kg ha-1 m3). Error bar represents
±SEM.
Figure 9 Interaction between cultivars,
irrigation and N regimes on NUE
(KgN kg-1). Error bar represents
±SEM.