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INVESTIGATION INTO CO 2 ABSORPTION OF THE MOST REPRESENTATIVE AGRICULTURAL CROPS OF THE REGION OF MURCIA

INVESTIGATION INTO CO2
ABSORPTION OF THE MOST
REPRESENTATIVE
AGRICULTURAL CROPS OF THE
REGION OF MURCIA
Prof. Micaela Carvajal
Profesora de Investigación
Consejo Superior de Investigaciones Científicas (CSIC)
INVESTIGATION INTO CO
2
ABSORPTION OF THE MOST
REPRESENTATIVE AGRICULTURAL CROPS OF THE REGION OF
MURCIA
Cesar Mota, Carlos Alcaraz-López, María Iglesias, M.C. Martínez-Ballesta
and Micaela Carvajal*
Departamento de Nutrición Vegetal
CEBAS-Consejo Superior de Investigaciones Científicas
30100-Espinardo, (Murcia), SPAIN
Project Coordinator and Director: Prof. Micaela Carvajal. E-mail:
mcarvaja@cebas.csic.es
1.-INTRODUCTION
1.1. CO
2
in Earth's Atmosphere
The phenomenon known as 'global warming’ occurs when energy
released by the Earth's crust is reflected and retained by certain atmospheric
gases, preventing the progressive cooling of the Earth. Without the intervention
of these gases, life as we know it would not be possible, as the heat released
by the planet would dissipate into space resulting in extremely low temperatures
on Earth. Included in such gases are carbon dioxide, nitrous oxide and
methane, which are released primarily by industry, agriculture, farming and the
burning of fossil fuels. The rate of industrial development on Earth means that
the concentration of these gases has risen by 30% since the last century
curtailing Mother Nature’s attempts to restore the natural balance of
concentrations of these atmospheric gases.
Of these gases, CO
2
is of particular significance, because of its effect on
the Earth’s climate and its permanence it is a gas that remains active in the
atmosphere for a long time. For example, of the CO
2
released into the
atmosphere, over 50% will take 30 years to disappear, 30% will remain for
many centuries and 20% will last for several million years (Solomon et al.,
2007).
Plants have the ability to capture atmospheric CO
2
, and through the
process of photosynthesis, metabolise it to produce sugars and other
compounds that are necessary for the plant’s normal development (Fig.
1. Photosynthesis (1)). In general, it can be concluded that plants, via the
process of photosynthesis, extract carbon from the atmosphere (in the
form of CO
2
) and convert it into biomass. On decomposition the biomass
becomes part soil (in the form of humus) and part CO
2
(through
respiration of micro-organisms that process the biomass (Fig. 1 (2)).
Figure 1. Carbon cycle: sources of CO
2
emissions and CO
2
sinks.
Various factors affect the amount of carbon accumulated in both plant
biomass and the soil. The felling of trees and the burning of vegetable matter,
such as occurs when forests are converted into farm or agricultural land, as well
as logging, releases the accumulated carbon in plants and the soil (Fig. 1 (3))
and this returns to the atmosphere in the form of CO
2
.
At present, an excess of CO
2
alters the natural balance of the carbon
cycle as previously described, acting as a decisive influence on climatic
conditions. On the one hand, CO
2
is captured from the atmosphere by plants
through photosynthesis. On the other, plant respiration, the burning of fossil
fuels and felling of trees for agricultural purposes increase the concentration of
carbon emissions in the atmosphere, which when combined with a high rate of
deforestation and insufficient attempts to replant trees, alter the balance
between capture and release. Therefore, the concentration of CO
2
in the
atmosphere is rising. Total CO
2
emissions from the agricultural and forestry
sectors supersede those released as a consequence of the burning of fossil
fuels in the transportation and energy sectors (Fig. 1 (4)).
1.2. Carbon Sinks
All systems and processes that extract and then store a gas or gases
from the atmosphere are called sinks. Using their primary function,
photosynthesis, plants act as carbon drainage systems. By this means, plants
absorb CO
2
, and offset the loss of this gas through respiration as well as that
released as a result of emissions from other natural processes (decomposition
of organic matter).
The absorption of CO
2
by plants constitutes an important element in the
global balance of carbon (C). On a global scale it is estimated that the Earth's
biosphere takes up nearly 2,000,000 tons of CO
2
per year (UNESA, 2005). This
amount is a result of the small differences between the photosynthetic
absorption of CO
2
and its loss through respiration, decomposition of organic
matter and different types of natural disturbances. Added to this amount is the
so-called net primary production in the biosphere (NPP), and it is this, which in
the long term, is stored in the sink.
The CO
2
captured by plants is the result of the differences between
atmospheric CO
2
absorbed during the process of photosynthesis and the CO
2
released by the atmosphere during respiration. This difference is converted into
biomass and tends to fluctuate between 45 and 50% of the plant’s dry weight.
Therefore, whilst CO
2
levels are high, both natural vegetation and agricultural
plants act as carbon drainage systems. When this is taken into account,
agriculture can become one of the most effective means in mitigating the
increase of atmospheric CO
2
.
The soil
To determine the amount of carbon captured by the ecosystem, the
amount of stable carbon in the soil must be considered. If accumulation of
carbon in the soil takes place at a slower rate than the accumulation of carbon
in the biomass, then the carbon stability in the soil is greater. Therefore, the soil
has a significant ability to store carbon due to the accumulation of vegetable
matter during decomposition, converting it into what is called carbon humus.
The pruning of trees and the shredding of their leaves can be considered as
loss of crop carbon when removed from the land or burned. However, if leaf
matter is left to decompose naturally, it becomes an effective way of
immobilising CO
2
in the long term (Lal, 1997). In fact, after one year of plant
matter accumulating on the ground, most of the carbon returns to the
atmosphere in the form of CO
2
. However, one-fifth to a third of this carbon stays
in the soil, as either live biomass or humus (Brady and Weil, 2004).
1.3. Photosynthesis
Photosynthesis is a metabolic process fundamental to all living
organisms as it involves using solar energy to biosynthesise cellular
compounds. Solar energy is not just a source of energy for green plants and
other photosynthetic autotrophs, but is ultimately the energy source of almost all
heterotrophic organisms, through the workings of biospheric food chains.
Furthermore, solar energy captured in the process of photosynthesis is the
source of nearly 90% of all energy used by humans to meet their heating,
electricity and energy needs, since carbon, petroleum and natural gas (fossil
fuels primarily used in industry), are the products left over from the
decomposition of biological matter generated millions of years ago by
photosynthetic organisms.
Photosynthesis is a process that occurs in two stages (Fig. 2). The first
stage is light-dependent (light reaction phase). This stage requires energy
directly from sunlight to generate chemical energy and a reducing agent, both of
which are used in the second stage. The light-independent stage (dark phase)
occurs when the products derived from light reactions are used to form covalent
carbon-carbon (C-C) bonds of carbohydrates from the CO
2
through the Calvin
Cycle. This process of photosynthesis takes place in the cell's chloroplast.
Figure 2. Diagram of photosynthesis.
In light reactions, solar energy is captured by pigments that absorb light,
and, with the aid of a water molecule, convert it into chemical energy (ATP) and
a reducing agent (NADPH). As a result, molecular O
2
is released. The general
equation for this first stage of photosynthesis is the following:
WATER + NADP
+
+P
i
+ ADP OXYGEN
+ H
+
+ NADPH + ATP
In the second stage of photosynthesis, the energy-rich products of the
first stage, NADPH and ATP, are used as sources of energy to carry out the
reduction of CO
2
and produce glucose. As a result, ADP and NADP
+
are
produced again. The second stage of photosynthesis is summarised as follows:
CO2 + NADPH
+ H
+
+ ATP GLUCOSE
+ P
i
+ NADP
+
+ ADP
This reaction is carried out by conventional chemical reactions catalysed
by enzymes that do not require light.
In light-independent reactions, CO
2
from the atmosphere (or from the
water in aquatic/marine photosynthetic organisms) is captured and reduced with
light
the addition of hydrogen (H
+
) to form carbohydrates [(CH
2
O)]. The assimilation
of carbon dioxide by organic compounds is known as carbon fixation or
assimilation. The energy used in the process originates from the first stage of
photosynthesis. Living beings cannot make direct use of light energy. However,
through a series of photosynthetic reactions, energy can be stored in the C-C
bonds of carbohydrates, which are later released in the process of respiration
and other metabolic processes.
Carbon fixation in C3, C4 and CAM plants
Plants have different metabolisms depending on their type of CO
2
fixation, and are classified into the categories of C-3, C-4 or CAM. The
efficiency of a plant’s water usage and rate of carbon fixation differs depending
on the plant.
C-3 plants: These plants keep their stomata open during the day to allow
fixation of CO
2
, thus leading to a continual loss of water through transpiration.
To avoid the risk of dehydration caused by an environmental disturbance, these
plants are able to close their stomata, leading to a decrease in photosynthetic
activity.
C-4 plants: Stomata are kept open during the day. These plants use
intermediaries in their cells to pump CO
2
, which allows the stomata to close
unexpectedly, hence allowing the process of photosynthesis to continue thanks
to CO
2
reserves.
CAM plants: Stomata remain open at night. Water loss through
transpiration is greatly reduced. These plants also have reserves of CO
2
with
which they can also close stomata without lessening their ability to
photosynthesise.
The properties of C-4 and CAM plants allow them to survive in
environments in which water is scarce.
Table 1. Some of the differences among C3, C4 and CAM plants.
Typical species of
economic importance
C3
wheat, barley,
pepper, fruit, rice,
tomatoes
C4
corn, sorghum, sugar
cane
CAM
pineapple, prickly
pear
% of flora worldwide
in number of species
89% <1% 10%
Typical habitat Ample distribution Warm areas and
grasslands
Humid areas and
tropics
First stable product
from CO
2
fixation
PGA Malate Malate
Anatomy Bundle sheath cells
not present/without
chloroplasts
Bundle sheath cells
with chloroplasts
(Kranz)
Succulence of cells
and plant tissue
Photo respiration Up to 40% of
photosynthesis
Not detectable Not detectable
Point of
compensation for the
assimilation of CO
2
40-100 µl l
-1
0-10 µl l
-1
0-10 µl l
-1
[CO
2
] inter cellular
during daylight (µl l
-1
)
200 100 10000
Frequency of stomata
(Stomata mm
-2
)
40 - 300 100 - 160 1 - 8
EUA (CO
2
g fixed by
kg H
2
O transpired)
1 - 3 2 - 5 10 - 40
Maximum rate of
growth (g m-
2
d
-1
)
5-20 40-50 0.2
Maximum productivity
(tons ha
-1
year
-1
)
10-30 60-80 Generally less than
10*
1.4. Effect of environmental stress factors on CO
2
fixation
Environmental stress factors such as salinity, desiccation, fluctuations in
temperature and the reduction in solar radiation alter plant structure and
metabolism, thereby affecting their growth and their role as CO
2
absorbers
(Martínez-Ballesta et al., 2009). Given that they are essential for the processes
of absorption and transportation of water and nutrients, such environmental
factors are key variables that affect plant development. This being the case, the
effect of these factors can have numerous consequences for agricultural crops,
both in terms of physiological responses in the individual plant in the short-term
to long-term changes in plant structure and function. Numerous studies have
shown that plants, when faced with certain environmental factors, react in
various ways that normally lead to water shortage (Kimball et al., 2002).
Given the severe desiccating nature of the atmosphere, controlling water
loss has always been a key aspect for plant survival. On the one hand, the flow
of water through a plant should be sufficient to maintain adequate nutrition and
assimilation of CO
2
. On the other, since assimilation and transpiration are
closely linked in almost all plants, the availability of water imposes a restriction
on total productivity and development (Steudle and Peterson, 1998). At the
same time, to prevent desiccation of surface areas, the intake of water through
the plant’s roots has to compensate for the loss of water through its leaves.
Given that the physiological processes are extremely sensitive to water
shortage, the ability to conserve sufficient amounts of water tends to constitute
the main problem in areas where the climate is warm and precipitation low.
The rise in temperatures could lead to an increase in photorespiration,
which is a mechanism used to protect the process of photosynthesis, and which
is not involved in CO
2
fixation (Sofo et al., 2005). The combined actions of
different environmental factors (water vapour in the atmosphere and the rise in
temperatures) could lead to a greater production of biomass, but only if plants
receive adequate support from other essential nutrients such as nitrogen,
phosphorus and potassium (human intervention could help in the provision of
nitrogen to natural ecosystems since this nutrient is left over from many of our
contaminating emissions when released into the environment).
It is predicted that we will see an increase in CO
2
fixation in the next 60
years due to the rise in temperatures. It is hoped that CO
2
fixation will increase
1% by every
o
C in areas where the average annual temperature is 30
o
C and
10% in areas where the average annual temperature is 10
o
C. The rate of
photosynthesis will increase between 25 and 75% in C3 photosynthetic plants
(those most commonly found in areas of medium and high latitudes) at double
today’s CO
2
concentrations. Data is less conclusive in the case of plants whose
methods of photosynthesis are similar to that of C4 plants, typically those of hot
areas, their response intervals ranging from 0% to an increase of 10 to 25%
(UNESA, 2005).
This problem implies the need to carry out research into the effect of
different environmental factors on CO
2
fixation ability and into deciphering the
water and nutritional needs of agricultural crops.
1.5. Agriculture in the region of Murcia
The agriculture of the Region of Murcia plays a fairly important role in the
GDP of Spain. It is one of the most lucrative farming regions in Spain and
Europe due to high productivity, which is much higher than the national
average. Agriculture in the Murcia region is orientated towards exportation,
which suggests strong agronomic infrastructure and an efficient
communications network. If we include all the indirect activities generated as a
result of the farming industry, this then becomes a notable element within the
context of the regional economy.
The region's excellent climate, combined with widespread adoption of
eco-friendly farming practices, markedly increases the remunerative importance
of this sector. The scarcity of water in the region has become a limiting factor
and has led to the current situation in which the irrigation of land is dependent
on underground water (which contains a large amount of saline due to
overexploitation as well as the intrusion of sea water) as the Tajo-Segura inter-
basin water transferral system has become insufficient to cover regional needs.
Agricultural crops of numerous varieties are the most significant products
of Murcia's agricultural industry: tomatoes, lettuce, peppers, artichokes, etc.,
although citrus fruit (particularly lemons) and grains are also important, followed
by vine fruits and other high-value orchard products, such as almonds,
peaches, plums, etc.
Overall, logging has little bearing on the economy and occupies only a
small area of the region. Forests are mainly located in the mountainous zones
and are not needed for regional requirements. Indigenous forests have suffered
from significant human incursions, so that the predominant species are now
replanted pines and poplars along the riverbanks.
The adoption of good agricultural practices and sustainable farming (as
in not clearing the ground, using exact quantities of fertilizer and when
necessary, refraining from burning crops and relying less on ploughing) would
halt the release of millions of tons of greenhouse gases. Therefore, a code of
good farming practice is being established to help protect the soil, manage
organic matter and soil structure, and conserve habitats, agricultural land, and
permanent pasture. This change in the agronomic model could lead to a
positive balance of CO
2
in farming
areas. With suitable preparation and training,
this sector can help mitigate the release of harmful gases through adaptation of
farming techniques, promotion of eco-friendly methodology and the more
efficient use of resources in farming machinery, making it ultimately more
efficient all round.
Therefore, as part of this project, this study has determined the
annual rate of CO
2
fixation
by the agricultural crops most representative of
the Region of Murcia, based on data obtained from biomass production
and their concentration of carbon. Only irrigated land totalling a surface
area greater than 1000 Ha was chosen. The amount of carbon fixation by
individual plants was calculated only considering the annual biomass
production of the plant, allowing total carbon fixation and CO
2
concentration to be calculated.
2. MATERIALS AND METHODS
2.1. Plant and processed material
For all the varieties analysed in the carbon fixation study, only the plant
or tree's annual production of biomass (both surface area (the fruit) and root),
was considered (IPCC, 2003).
Crops
Tomato, pepper, watermelon, melon, lettuce and broccoli
Specimens were collected during the final stages of cultivation. Three
plants from each variety were extracted manually from the soil with a spade
being careful not to harm the secondary roots and were put into individual
plastic bags for processing at the laboratory. The fruit, leaf, stalk and root were
subsequently separated and weighed to determine the fresh weight. Specimens
were then put into a laboratory hot-air oven at 70
o
C until constant weight was
obtained to determine dry weight. The time taken for the drying process can
vary depending on the humidity and total weight of the specimen. Once the dry
weight for each part of the specimen was obtained, the crops were ground
using an IKA model A10 analytical laboratory grinder. A homogeneous result
was obtained with particles of from 5 to 7 mm in diameter.
The total amount of
carbon was determined as described in the following analysis.
Photograph 1. Processing of agricultural crops.
Grains
Oats, barley and wheat
A total of 10 specimens of each variety were collected from the farm
during the production stage. They were extracted manually and labelled
accordingly in airtight bags until arrival at the laboratory, where they were then
separated into above-ground and root parts for subsequent weighing and
statistical analysis to determine the fresh weight of each plant. To determine the
dry weight, the specimens were put into a hot air drying chamber at 70
o
C for
approximately 5 days and were then weighed on laboratory precision scales.
The specimens were ground as explained in the previous section and carbon
content was determined as described below.
Photograph 2. Laboratory processing of grains.
Fruit
Apricot, plum, peach, and grape
A destructive methodology was used to collect the fruit tree specimens
that consisted of uprooting, by heavy machinery, three 17-year-old trees. The
trees were then divided into sections (trunk, branches, and root) using a
chainsaw. The leaves were then completely removed by hand along with the
current year’s young branches. The rest of the older trunk and branches were
divided for subsequent weighing. Specimens were bagged and labelled
according to parts for transferral to the laboratory. The root was processed in
the same manner after being cleaned of any remaining soil and residue. This
year’s roots were cut and weighed. As was the case for the above ground
section of the tree, a representative sample of the root was taken to the
laboratory for processing.
Wooden crates with a capacity of 30 kg and a hydraulic pallet truck were
used to transport the specimens from the farm to the cooperative. At the
cooperative, specimens were weighed separately on industrial floor scales
comprising corrugated, anti-slip, steel lifting beams, four mobile weighing
platforms and a handling terminal.
The fruit specimens were taken from fruit collected at the farm. A
representative sample of the fruit was taken to the laboratory in order to obtain
the dry weight and the total amount of carbon in a similar process to that
described previously. The total fruit crop amount was calculated from the
average obtained from all the trees in the sample plot.
Photograph 3. Processing the fruit.
Citrus fruit
Lemon, orange, and mandarin
To calculate the CO
2
fixation of citrus fruits and annual quantification of
CO
2
, samples from 15-year-old trees were used. Extraction comprised pulling
down both the above- and below- ground parts of the trees using a Caterpillar
power shovel 983G (135 kW). After the trees were felled, the same shovel was
used to separate the trees into three parts from which the fresh weight could be
obtained. A chain saw was used to separate the branches (those which had
been previously used to collect the fruit), the trunk and the roots (once any
remaining soil and residue had been removed), and fresh weight was then
determined using a similar procedure to that described in the previous section.
The total fruit crop was calculated from the total of each tree collected in the
previous crop(s) corresponding to a full year’s growth.
A representative sample from each part of the tree, together with the fruit
specimens, were collected to determine the dry weight at the laboratory as
previously described.
The fact that leaf biomass is renewed every three years, and that total
weight of the above-ground part of the plant and the root is in a 70/30 ratio with
regards to the tree's total biomass, needs to be considered in order to calculate
the total annual carbon fixation per tree (Morgan et al., 2006). Measurements
were carried out as follows.
Photograph 4. Processing the citrus fruit.
2.2. Determining total amount of carbon
The total amount of carbon was analysed in sub-samples (around 2-3 mg
PS) of leaves, stalks, fruit and roots using an NC-Thermo Finnigan 1112 EA
Elemental Analyser (Thermo Finnigan-, Milan, Italy).
Photograph 5. CEBAS-CSIC Carbon Analyser.
3. RESULTS
3.1 Determining the amount of carbon and CO
2
fixation in herbaceous
plants
The results of the CO
2
calculations of herbaceous plants, tomato,
pepper, watermelon, melon, lettuce and broccoli are shown in tables 1 to 6.
The tables show the average values for annual biomass and CO
2
fixation
based on the percentage of carbon for each section of the plant. Taking into
account the annual growth of these plants, the total amount of carbon has been
determined for the whole plant, keeping in mind the total production of the plant,
its fruit and seeds.
In the tomato plants (Table 1) a greater concentration and fixation of
carbon was observed than in the pepper plants (Table 2) due to a greater
amount of biomass in tomato than pepper. However, when the total amount of
carbon per hectare is calculated, the differences between these two plants
diminish due to the pepper plant having a greater plantation density (2.2 plants
m
2
) than the tomato (2 plants m
2
). The region currently has a great number of
tomato varieties and uses different forms of cultivation. For the purposes of this
study, salad tomatoes (Corvey variety) cultivated in soil were used.
Table 3 shows the CO
2
absorption rates and carbon concentration of
watermelon. The values per plant are very similar to those for tomato; however,
the fact that plantation density is lower also reduces the total amount of fixed
carbon per hectare. When the data obtained for the watermelon is compared
with that for melon (Table 4), it is clear that even though the results for carbon
absorbed by the melon are much lower (approximately half), due to the
watermelon’s greater biomass, the total per hectare is similar as a result of
greater plantation density.
Table 5 shows the difference in carbon concentration in two agriculturally
significant lettuce varieties. As can be seen from the values obtained per plant,
values are much higher in the Romaine variety due to its greater biomass in dry
weight. However, there are no great differences between these varieties in
terms of amount of carbon fixation per square metre due to the Cogollo variety
having a much greater plantation range than Romaine. When calculating the
total amount of carbon per hectare and year, it is important to remember that
this region produces three annual harvests of these types of crops.
Table 6 shows that there are no great differences between the two
different varieties of broccoli with respect to absorption efficiency of CO
2
,
although it is somewhat greater in the Naxos variety due to its greater biomass.
As is the case with lettuce, when the amount of carbon is calculated per year
and hectare, the fact that this region produces three annual harvests must be
considered.
The results obtained for cauliflower (Table 7) are fairly high compared to
those of the other Brassica, broccoli. These results are due primarily to its
greater biomass, since plantation density is similar. Therefore, the results for
carbon fixation per plant and square metre are greater.
The greatest increases in CO
2
fixation for agricultural plants can be
observed in artichokes (Table 8). This result is due to its greater biomass in dry
weight. Consequently, although the plantation density of artichokes is lower, it
results in a greater concentration of carbon per square metre.
Table 1. Modular values of carbon and CO
2
increase
in different sections of biomass (g) in tomatoes.
Fresh
weight Dry weight
Humidity C % Carbon total
Carbon total PLANT TOTAL
TOMATO
(Plant g
-1
)
(Plant g
-1
)
% (% Dry weight)
(m g
-2
year
-1
)
(T ha
-1
year
-1
) C g Plant
-1
CO
2
g plant
-1
Root 134 22.5 83.23 38.96 17.5
0.2
8.8
32.3
Stalk 1,434 296.8 79.30 40.36 240
2.4
120
440
Leaves 866 169.7 80.40 40.99 139
1.4
69.6
255
Fruit 3,394 510.8 84.95 46.05 470.4
4.7
235.2
862
Total 5,827 1,000 867
8.7
433
1,590
Plantation density: 2 plants m
2
Table 2. Modular values of carbon and CO
2
increase
in different sections of biomass (g) in peppers.
Fresh weight
Dry weight
Humidity C % Carbon total
Carbon total PLANT TOTAL
PEPPER (Plant g
-1
) (Plant g
-1
)
% (Dry weight %)
(g m
-2
year
-1
) (T he
-1
year
-1
) C g plant
-1
CO
2
g plant
-1
Root 53.4 30.3 43.23 43.15 28.8
0.3
13.1
48.0
Stalk 458 269.1 41.24 40.82 241.7
2.4
109.8
402.6
Leaves 519 305.6 41.12 31.14 209
2.1
95.2
349.1
Fruit 683 135 80.25 46.34 137.5
1.4
62.5
229.2
Total 1,713 740 617
6
281
1,029
Plantation density: 2.2 plants m
2
Table 3. Modular values of carbon and CO
2
increase
in different sections of biomass (g) in watermelon.
Fresh weight
Dry Weight
Humidity
C % Carbon total
Carbon total PLANT TOTAL
WATERMELON
(Plant g
-1
) (Plant g
-1
)
% (Dry weight %)
(g m
-2
year
-1
) (T he
-1
year
-1
) C g plant
-1
CO
2
g plant
-1
Root 46.8 8.5 81.87 37.83 1.3
0.01
3.2
11.73
Stalk 2,369 285 87.99 39.29 45
0.5
112
411
Leaves 2,691 322 88.05 37.54 48
0.5
121
444
Fruit 15,989 398 97.51 42.71 68
1
170
623
Total 21,096 1,013 162
1.6
406
1,489
Plantation density: 0.4 plants m
2
Table 4. Modular values of carbon and CO
2
increase
in different sections of biomass (g) in melon.
Fresh weight
Dry weight
Humidity
%C Carbon total
Carbon total
PLANT TOTAL
MELON (Plant g
-1
) (Plant g
-1
)
% (Dry weight %)
(g m
-2
year
-1
) (T he
-1
year
-1
) C g plant
-1
CO
2
g plant
-1
Root 23.6 5 80.53 39.69 2
0.02
2
7.3
Stalk 1071 134 87.47 33.62 45.1
0.5
45.1
165.4
Leaves 764 90 88.17 36.72 33
0.3
33.0
121.0
Fruit 2972 319 89.25 43.43 138.5
1.4
138.5
507.8
Total 4,831 549 219
2
219
802
Plantation density: 1 plant m
2
Table 5. Modular values of carbon and CO
2
increase
in different sections of biomass (g) in different lettuce varieties.
Fresh weight
Dry weight
Humidity
C % Total carbon
Total carbon
PLANT TOTAL
COGOLLO
(Plant g
-1
) (Plant g
-1
)
% (Dry weight %)
(g m
-2
year
-1
) (T he
-1
year
-1
) C g plant
-1
CO
2
g plant
-1
Root 56.6 12.8 77.44 39.90 229.8
2.3
5.1
18.7
Stalk 96.6 6.1 93.70 36.75 100.9
1.0
2.2
8.1
Leaves 430.2 22.3 94.81 35.08 352.5
3.5
7.8
28.6
Total 583.4 41.2 682.7
6.8
15.1
55.4
Fresh weight
Dry weight
Humidity
C % Carbon total
Carbon total
PLANT TOTAL
ROMAINE
(Plant g
-1
) (Plant g
-1
)
% (% Dry weight)
(g m
-2
year
-1
) (T he
-1
year
-1
) C g plant
-1
CO
2
g plant
-1
Root 65.4 18.4 71.90 38.69 138.9
1.4
7.1
26.0
Stalk 185.2 12.6 93.17 37.91 93.1
0.9
4.8
17.6
Leaves 1121.5 65.8 94.13 35.79 459.2
4.6
23.5
86.2
Total 1372.1 96.8 691.2
6.9
35.4
129.8
Plantation density: Cogollo: 15 plants m
2
. Romaine: 6.5 plants m
2
Table 6. Modular values of carbon and CO
2
increase
in different sections of biomass (g) in two varieties of broccoli.
Fresh weight
Dry weight
Humidity C % Carbon total
Carbon total PLANT TOTAL
BROCCOLI-
PARTHENON (Plant g
-1
) (Plant g
-1
)
% (Dry weight %)
(g m
-2
year
-1
) (T he
-1
year
-1
) C g plant
-1
CO
2
g plant
-1
Root 228.5 42.9 81.23 41.48 186.8
1.9
17.8
65.3
Stalk 600.9 63.0 89.52 41.50 274.5
2.7
26.1
95.7
Leaves 103.9 11.0 89.41 42.04 48.6
0.5
4.6
16.9
Inflorescence 207.4 22.2 89.57 43.98 101.8
0.5
9.7
32.5
Total 1140.7 139.1 611.75
6.1
58.2
210.4
Fresh weight
Dry weight
Humidity C % Carbon total
Carbon total PLANT TOTAL
BROCCOLI-NAXOS
(Plant g
-1
) (Plant g
-1
)
% (% Dry weight)
(g m
-2
year
-1
) (T he
-1
year
-1
) C g plant
-1
CO
2
g plant
-1
Root 196.5 43.9 77.66 39.35 181.4
1.8
17.3
63.4
Stalk 848.5 101.7 88.01 40.00 427.1
4.3
40.7
149.2
Leaves 51.4 6.4 87.55 41.81 27.9
0.3
2.7
9.9
Inflorescence 186.5 19.9 88.55 44.21 96.0
0.5
4.4
16.1
Total 1182.7 161.9 682.4
6.8
65.0
238.7
Plantation density: 3.5 plants m
2
Table 7. Modular values of carbon and CO
2
increase
in different sections of biomass (g) in cauliflower.
Fresh
weight Dry weight Humidity C % Carbon total Carbon total PLANT TOTAL
CAULIFLOWER
(g plant
-1
) (g plant
-1
) % (% Dry weight) (g m
-2
year
-1
) (T he
-1
year
-1
) g C Plant
-1
g CO
2
Plant
-1
Root 83.75 20.7 75.31 38.19 83.0
0.8
7.9
29.0
Stalk 235.35 24.1 89.76 36.27 97.2
1.0
8.7
31.9
Leaves 1,246.50 118.9 90.46 38.40 479.4
4.80
45.70
167.60
Inflorescence 801.00 74.5 90.69 41.77 326.7
3.3
31.1
114.0
Total 2,366.60 238.2 986
9.9
93.4
342.5
Plantation density: 3.5 plants m
2
Table 8. Modular values of carbon and CO
2
increase
in different sections of biomass (g) in artichoke.
Fresh weight Dry weight
Humidity % C Carbon total
Carbon total PLANT TOTAL
ARTICHOKE (g plant
-1
) (g plant
-1
) % (% Dry weight)
(g m
-2
year
-1
) (T he
-1
year
-1
) g C Plant
-1
g CO
2
Plant
-1
Root 827 277.5 66.5 42.20 82
0.8
117.1
429.4
Stalk 1281 397.5 69.0 39.00 108.5
1.1
155
568.3
Leaves 2281 439 80.7 39.15 120.3
1.2
171.6
629.2
Inflorescence 598 146 75.7 42.33 43.2
0.4
61.8
226.6
Total 4987 1260 354
3.5
506
1,854
Plantation density: 0.7 plants m
2
3.2 Calculation of CO
2
absorption and carbon content in grains
In tables 9, 10 and 11 the total amount of annually absorbed carbon in
grams per plant is shown along with the sections of the biomass in oats, barley
and wheat, as well as the total amount of CO
2
absorbed by these grains. As the
tables show, the three grain varieties do not exhibit any great differences in the
various absorption levels per plant. However, if we estimate the CO
2
fixation
amount per square metre, the values are somewhat lower for barley, due to its
lower plantation density.
Table 9. Annual values of CO
2
absorption and assimilated carbon in oats.
Fresh weight
Dry weight
Humidity
% C Carbon total
Carbon total
PLANT TOTAL
OATS (g Plant
-1
) (g Plant
-1
) % (% Dry weight)
(g m
-2
year
-1
) (T he
-1
year
-1
) g C plant
-1
g CO
2
plant
-1
Root 4.7 0.4 91.03 34.21 17.5
0.2
0.1
0.37
Surface part 18.5 6.7 63.89 42.02 360.4
3.6
2.8
10.27
Total 23.1 7.1 378
3.8
3.0
10.63
Plantation density: 128 plants m
2
Table 10. Annual values of CO
2
absorption and assimilated carbon in barley.
Fresh weight
Dry weight
Humidity % C Carbon total
Carbon total PLANT TOTAL
BARLEY (g Plant
-1
) (g Plant
-1
) % (% Dry weight)
(g m
-2
year
-1
) (T he
-1
year
-1
) g C plant
-1
g CO
2
plant
-1
Root 2.1 0.9 53.63 27.65 24.9
0.2
0.2
0.7
Surface part 61.8 7.9 87.29 42.73 300
3.0
3
12.3
Total 63.9 8.8 325
3.2
3.6
13.0
Plantation density: 100 plants m
2
Table 11. Annual values of CO
2
absorption and assimilated carbon in wheat.
Fresh weight
Dry weight Humidity % C Carbon total Carbon total PLANT TOTAL
WHEAT (g Plant
-1
) (g Plant
-1
) % (% Dry weight) (g m
-2
year
-1
) (T he
-1
year
-1
) g C plant
-1
g CO
2
plant
-1
Root 1.5 0.7 49.80 26.54 23.2 0.2 0.2
0.7
Surface part 16.8 6.7 60.23 42.26 354 3.5 2.8
10.3
Total 18.3 7.4 377.2 3.8 3.0
11.0
Plantation density: 125 plants m
2
3.3. Calculation of total carbon and CO
2
fixation in fruit trees
The results of the calculations of CO
2
in apricot, plum, peach, nectarine,
grape, lemon, orange and mandarin trees are shown in tables 12 to 16.
The tables record the average total values for biomass and CO
2
fixation
in percentage of carbon for each section of the plant. The total amount of
carbon of the whole plant is calculated taking into account the annual
production of fruit and the plant’s annual growth rate.
Table 12 contains data on the analysis of the apricot tree, in which a
greater concentration of carbon and CO
2
fixation per tree was found than in the
other fruit trees analysed. However, it is important to consider that the density of
apricot plantation is half that of the other fruit trees. The peach tree exhibited
higher results per square metre (Table 14). In fact, if we consider only the
content of carbon and CO
2
fixation per square metre, the apricot would be the
species with the lowest values, followed by the plum (Table 13). The highest
values are seen in the peach and nectarine (Tables 14 and 15). The plum tree
has the lowest dry weight (biomass) of the four analysed, which would indicate
a greater capacity to fix CO
2
and accumulate carbon.
The data obtained for grapes (Table 16) shows that in spite of having
approximately half the dry weight of nectarine, these two plants have similar
values for carbon accumulation per square metre. On the other hand, when the
results for carbon accumulation and CO
2
fixation are compared per vine with
the data obtained from the fruit trees, much lower values are exhibited (up to
75% lower if we compare it with the apricot tree).
Table 12. Total CO
2
accumulated annually per tree, per section of biomass in apricot .
Fresh
weight Dry weight
Humidity % C Carbon total
Carbon total TREE TOTAL
APRICOT (g tree
-1
) (g tree
-1
) % (% Dry weight)
(g m
-2
year
-1
)
(T he
-1
year
-1
) g C tree
-1
g CO
2
tree
-1
Root 25,217 15,130 40.00 43.04 132.8
1.3
6,512
23,870
Branches 10,185 6,057 40.53 46.74 57.8
0.6
2,831
10,381
Leaves 12,081 5,074 58.00 45.13 46.7
0.5
2,290
8,396
Fruit 125,000 18,588 85.13 64.5 174.3
1.7
8,545
31,331
Trunk 10,297 6,134 40.53 46.74 58.5
0.6
2,867
10,512
Total 182,780 50,983 470.1
4.7
23,045
84,498
Plantation density: 0.0204 trees m
2
Table 13. Total CO
2
accumulated annually per tree, per section of biomass in plum.
Fresh weight Dry weight Humidity % C Total carbon
Total carbon
TREE TOTAL
PLUM (g Tree
-1
) (g Tree
-1
) % (% Dry weight)
(g m
-2
year
-1
)
(T he
-1
year
-1
)
g C tree
-1
g CO
2
tree
-1
Root 12,600 7,840 37.78 48.21 215.0
2.2
3,780
13,859
Branches 2,882 1,487 48.40 47.09 39.9
0.4
700
2,568
Leaves 1,737 722 58.43 42.41 17.5
0.2
306
1,123
Fruit 75,000 10,583 85.89 49.38 297.9
3.0
5,226
19,161
Trunk 4,792 2,355 50.86 47.09 63
1
1,109
4,066
Total 97,011 22,987 633.3
6.3
11,121
40,777
Plantation density: 0.057 trees m
2
Table 14. Total CO
2
accumulated annually per tree, per section of biomass in peach.
Fresh weight
Dry weight
Humidity % C Carbon total
Carbon total TREE TOTAL
PEACH (g Tree
-1
) (g Tree
-1
) % (% Dry weight)
(g m
-2
year
-1
)
(T he
-1
year
-1
)
g C tree
-1
g CO
2
tree
-1
Root 15,308 9,832 35.77 48.02 268.9 2.7 4,721
17,312
Branches 4,200 2,259 46.22 45.56 58.9 0.6 1,029
3,773
Leaves 11,700 5,005 57.22 44.13 125.9 1.3 2,209
8,099
Fruit 78,000 8,182 89.51 46.84 218.5 2.2 3,833
14,053
Trunk 7,273 3,911 46.22 45.56 101.6 1.0 1782
6,534
Total 116,481 25,122 773.8 7.7 13,574
49,771
Plantation density: 0.057 trees m
2
Table 15. Total CO
2
accumulated annually per tree, per section of biomass in nectarine.
Fresh weight
Dry weight
Humidity % C Carbon total
Carbon total TREE TOTAL
NECTARINE (g Tree
-1
) (g Tree
-1
) % (% Dry weight)
(g m
-2
year
-1
)
(T he
-1
year
-1
)
g C tree
-1
g CO
2
tree
-1
Root 13,308 8,548 35.77 48.02 234.0
2.3
4,105
15,052
Branches 3,200 1,721 46.22 45.56 41.9
0.4
784
2,875
Leaves 9,700 4,150 57.22 44.13 52
0.5
1,831
6,714
Fruit 75,000 9,608 87.19 49.01 299.2
3
4,709
17,266
Trunk 5,273 2,836 46.22 45.56 80
0.8
1,292
4,738
Total 106,481 26,862 739.8
7
12,721
46,644
Plantation density: 0.057 trees m
2
Table 16. Annual amounts of CO
2
absorption and assimilated carbon in grape.
Fresh weight Dry weight Humidity % C Carbon total
Carbon total
TREE TOTAL
GRAPE (g Tree
-1
) (g Tree
-1
) % (% Dry weight)
(g m
-2
year
-1
)
(T he
-1
year
-1
)
g C tree
-1
g CO
2
tree
-1
Root 6,242 2,788 55.33 44.98 103
1.0
1,254
4,599
Branches 3,615 1,387 61.62 45.89 52.2
0.5
637
2,335
Leaves 5,187 1,737 66.58 46.18 65.8
0.7
802
2,941
Fruit 47,500 6,992 85.28 47.17 270.4
2.7
3,298
12,093
Trunk 1,624 800 50.74 45.89 30
0
367
1,347
Total 64,168 13,704 521.4
5.2
6,358
23,315
Plantation density: 0.082 plants m
2
3.4 Determination of CO
2
in citrus plants
In each table corresponding to the citrus fruits (Tables 17-19) the total in
tonnes according to variety and section of biomass are shown, as well as the
total annual amount of assimilated CO
2
per tree.
The results for lemon (Table 17) were the highest, not only when
compared to the rest of the citrus plants, but also when compared to the rest of
the orchard crops. In this case, lemon shows higher levels of fixation and
accumulation as much per tree (due to its having the greatest biomass) as per
square metre. In general, it seems that lemon has the greatest capacity for CO
2
fixation. The orange (Table 18) shows much lower values than lemon but similar
when a general comparison is made with the other fruit trees, whilst mandarin
showed the lowest amounts (Table 19).
Table 17. Annual CO
2
absorption amounts and assimilated carbon in lemon trees.
Fresh weight Dry weight Humidity
% C Carbon total
Carbon total
TREE TOTAL
LEMON (g Tree
-1
) (g Tree
-1
) % (% Dry weight)
(g m
-2
year
-1
)
(T he
-1
year
-1
)
g C tree
-1
g CO
2
tree
-1
Root 26,833 13,953 48.00 43.87 174.9
1.7
6,121
22,446
Branches 17,000 8,898 47.66 44.23 112.4
1.1
3,935
14,430
Leaves+stalk
36,667 15,576 57.52 43.30 192.7
1.9
6,744
24,729
Fruit 200,000 26,540 86.73 42.51 322.3
3.2
11,282
41,368
Trunk 4,330 2,266 47.66 44.23 28.6
0.3
1,080
3,960
Total 284,830 67,233 831
8.3
29,163
106,933
Plantation density: 0.028 trees m
2
Table 18. Annual CO
2
absorption amounts and assimilated carbon in orange trees.
Fresh weight Dry weight Humidity % C Carbon total
Carbon total
TREE TOTAL
ORANGE (g Tree
-1
) (g Tree
-1
) % (% Dry weight)
(g m
-2
year
-1
)
(T he
-1
year
-1
)
g C tree
-1
g CO
2
tree
-1
Root 7,555 2,420 67.97 44.13 44.8
0.4
1,068
3,916
Branches 6,217 3,362 45.93 44.13 62.3
0.6
1,483
5,439
Leaves+stalk 8,893 3,945 55.64 40.80 67.6
0.7
1,610
5,902
Fruit 100,000 20,568 82.86 41.90 362.0
3.6
8,618
31,599
Trunk 2,845 1,538 45.93 44.13 28.5
0.3
679
2,489
Total 133,510 31,833 565.2
5.6
13,458
49,345
Plantation density: 0.042 trees m
2
Table 19. Annual CO
2
absorption amounts and assimilated carbon in mandarin trees.
Fresh weight
Dry weight
Humidity % C Carbon total
Carbon total TREE TOTAL
MANDARIN
(g Tree
-1
) (g Tree
-1
) % (% Dry weight)
(g m
-2
year
-1
)
(T he
-1
year
-1
) g C tree
-1
g CO
2
tree
-1
Root 2,858 957 66.52 44.98 17.9
0.2
430.5
1578.5
Branches 1,050 632 39.78 44.98 11.8
0.1
284.4
1042.8
Leaves+stalk
4,667 2,239 52.02 40.57 37.8
0.4
908.4
3330.8
Fruit 80,000 15,496 80.63 43.50 280.8
2.8
6740.8
24716.3
Trunk 435 262 39.78 44.98 5
0.05
118
432
Total 89,010 19,587 353
3.5
8,482
31,101
Plantation density: 0.042 trees m
2
In summary, figures 3 and 4 show comparisons between the annual
fixation of the different citrus crops per square metre (m
2
in Figure 1) and per
tree/plant (Figure 2). In figure 2, trees have been separated from other crops due to
their different scale. The data show that 50% of crops (both arboreal and
horticultural) fix more than 500 grams of carbon per square metre. In other words,
more than 1800 grams of CO
2
per square metre.
tomate
pimiento
sandía
melón
lechuga
broculi
alcachofa
coliflor
avena
cebada
trigo
albaricoquero
ciruelo
melocotonero
nectarina
uva de mesa
limonero
naranjo
mandarino
C fijado anual (g m
-2
)
0
200
400
600
800
1000
1200
Figure 3. Total annual carbon fixation per crop expressed per square metre (m
2
).
tomate
pimiento
sandía
melón
lechuga
bróculi
coliflor
alcachofa
avena
cebada
trigo
C anual fijado (g planta
-1
)
0
100
200
300
400
500
600
albaricoquero
ciruelo
melocotonero
nectarina
uva de mesa
limonero
naranjo
mandarino
C fijado anual (g arbol-1)
0
5000
10000
15000
20000
25000
30000
35000
Figure 4. Total annual carbon fixation per crop (per plant and tree).
4. DISCUSSION
The data shown in this study has been obtained from agricultural crops
from the Region of Murcia. Specimens were collected from different areas of the
region where the crop species is most representative. Therefore, even though
growth and variables will be different in other regions, this study reflects the
general pattern in this area.
This study focuses on the CO
2
fixation ability per plant in order to
compare the results among different agricultural crops. However, for a more in-
depth study of the total values obtained, results per hectare combined with
knowledge of plantation density need to be taken into account.
In general, of the data obtained in this work, we can affirm that of the
agricultural crops analysed, artichoke is the most efficient in terms of CO
2
fixation, followed by tomato and watermelon (Figure 1). However, when results
per square metre are analysed, cauliflower is the most efficient crop and
artichoke then becomes one of the least efficient together with watermelon and
melon. When grain varieties are analysed per individual plant they are found to
be very efficient in CO
2
fixation, superseding all values obtained for agricultural
plants. However, when analysed per square metre, results drop significantly to
much lower amounts.
Among the fruit trees analysed, peach and nectarine are the most
efficient fixers of CO
2
per square metre cultivated, followed by plum, and, lastly,
apricot. Although apricot shows the best CO
2
fixation per tree, its efficiency is
reduced because its plantation range (7m x 7m) is much greater than that of the
other fruit trees (3.5m x 5m). On the other hand, if we take into account that the
relation of kg of carbon to kg of dry matter is very similar for all varieties, this
indicates that, aside from plantation density, the natural growth ability of these
species is a factor that affects CO
2
fixation per plant. For example, the plum
tree is cultivated with the same size plantation density as the peach and
nectarine trees. However, CO
2
fixation capacity is reduced when compared to
the other varieties due to its slower growth.
Of all the orchard crop species analysed in this study, the lemon shows
the greatest ability to fix CO
2
both per square metre and per tree. In this case,
the most relevant factor for CO
2
fixation is the lemon tree’s abundant natural
growth, which it maintains throughout its lifecycle, resulting in leafier trees with
greater surface foliage, therefore giving it a greater ability to fix CO
2
. In modern
agriculture, orange and mandarin are cultivated much less intensively than
lemon. However, in spite of their lower plantation range, their ability to fix CO
2
is
much lower than lemon, peach and nectarine, which have a lower dry weight
than orange. In this case, the curtailing factor for the CO
2
fixation of orange
trees is plantation density.
Lastly, grape cultivation shows more than acceptable CO
2
absorption
rates as compared to those obtained for the rest of the species, especially
considering that it has the lowest biomass. In this case, CO
2
fixation is benefited
by a high plantation density (3.5m x 3.5m).
An important factor to consider is the quantity of waste matter obtained
from each crop and the use made of it. For example, plant material obtained
from tree pruning could lead to a soil carbon fixation rate of between 20 and
35% of carbon concentrate in one year on decomposition (Brady and Weil,
2004). Such a practice will improve soil conditions and reduce CO
2
emissions
into the atmosphere, as the burning of waste and crop matter is not only a
destructive act that generates CO
2
but also ruins the soil due to, amongst other
factors, the elimination of small insects and micro-organisms in the outer layers
of the soil (Blanco-Roldan and Cuevas, 2002). Furthermore, the potential to use
this by-product as raw material from which to generate renewable energy
sources like, for example, bio-diesel should be kept in mind. If we combine
waste from pruning with that generated from the handling and/or conversion of
fruit and vegetable products in industry (skin, pulp, stones and seeds) we can
obtain a significant quantity that can then be converted to bio-fuel, aromas,
animal feed and/or water, either for irrigation purposes or as purified water
(Biodisol.com, 2009). All these by-products will increase the ecological
efficiency of crops and lead the way towards completely sustainable agriculture.
The type of fertilizer used for each crop also needs to be considered. The
massive use of chemical fertilizers in the farming industry has increased
concern over matters such as decline in soil fertility and the increase in
greenhouse gas emissions. The draining of soil nutrients is a result of the
increase in pressure on agricultural land giving rise to a greater outward flow of
non-replenished nutrients (Wopereis et al., 2006). This is why organic farming
methods are needed to ensure that intensive farming does not endanger
sustainable use of the soil. However, small producers are reluctant to use
organic matter and compost due to the uncertainty of their benefits and
efficiency. In fact, a disadvantage of organic farming is that yields are normally
lower compared to those obtained by conventional farming methods (Mäder et
al., 2002; Dumas et al., 2003) because organic fertilizers provide nutrients more
slowly than mineral fertilizers and do not distribute nutrients as equally (Båth,
2000; Kirchmann et al., 2002; Gunnarsson, 2003). Therefore, crops cultivated
with organic fertilizers normally grow more slowly when compared with plants
cultivated with more easily available mineral fertilisers (Robertson et al., 2000).
Whilst it has not been conclusively shown that organic products are more
nutritive than conventional products (Winter, 2006) it has been observed that
organic fertilisers lead to a reduction in greenhouse gases (Matson et al., 1990).
Agricultural fertilisers can be considered the most significant anthropogenic
source of N
2
O, contributing to 70% of greenhouse gases (Bouwman 1994;
Watson et al., 1992).
The results of this study also suggest possible political inroads that need
to be taken if atmospheric CO
2
fixation is to increase. Firstly, crops must be
cultivated over a broader range in areas where forest cover is scarce. And
secondly, a greater water investment will result in an increase in agricultural
biomass. In this respect, the semi-desert climate of much of the Region of
Murcia leads to high incidences of evapor-transpiration and as a result a greater
demand for water (Cubasch et al., 2001).
5. CONCLUSION
As can be inferred from this study, we depend on plants to counteract the
effects of global warming. Therefore, the solution to climate change necessarily
depends on conserving as much crop land as possible. We should optimise the
carbon fixation capacity of plants by adopting the best agronomic practices and
utilisation of crop by-products. Furthermore, the powerful ability of plants to
adapt, which has allowed them to weather huge changes for millions of years,
should be used as a basis for scientific study to allow us to evaluate the state of
our agricultural industry for future climatic scenarios.
Therefore, the results of this study highlight the need to provide our
region’s agricultural industry with greater water sources that will ensure an
increase in agricultural biomass and therefore a greater atmospheric fixture of
CO
2
. Furthermore, we need to commit to reusing organic by-products for energy
sources, fertilisers and even water, taking advantage of moisture remaining in
the organs and tissues of the plant that are not used.
Acknowledgements
The authors would like to thank the following companies and associations for their
cooperation in the extraction of specimens, technical support and advice during this study:
LANGMEAD FARMS, CEBAS-CSIC experimental farm, JOSÉ PEÑALVER FERNÁNDEZ,
CDTA EL MIRADOR, MORTE QUILES, FRUTAS ESTHER, PATRICIO PEÑALVER AZNAR,
FRUTAS TORERO, APROEXPA and FECOAM
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... In general, plants absorb carbon from the atmosphere (in CO2) and transform it into biomass through photosynthesis. Biomass becomes part of the soil (in the form of humus) and part of CO2 (via the respiration of microorganisms that process biomass) during the decomposition process [13]. To be able to absorb carbon dioxide, plants must have stomata that enable CO2 to enter [12]. ...
... Plants, through photosynthesis, extract carbon from the atmosphere (in the form of CO2) and convert it into biomass. In the decomposition process, biomass becomes part of the soil (in the form of humus) and part of CO2 (through the respiration of microorganisms that process biomass [13]. ...
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The creation of Open Green Spaces is one of the options for mitigating the impact of global warming. In order to maximize the function of urban forests as carbon dioxide absorbers, plant species selection for urban forests must be considered. The goal of this study was to compare the ability of single-leaf and compound-leaved plants growing in urban forests to absorb carbon dioxide. Exploratory survey methods with purposive sampling were used. The single-leaf plant, B. asiatica (520 cm ² ), had the maximum leaf area, whereas the single-leaf species, M. elengi had the lowest leaf area (47.50 cm ² ). The plant with the highest water content in leaves was found in single-leaf plants, B. asiatica (ranging from 74.67 percent to 77.32 percent), while plant F.decipiens from the compound-leaf plant had the lowest water content (ranging from 44.34 percent to 46.14 percent). The plant with the highest percentage of carbohydrate mass at 06.00 am was M. elengi (531.63 percent), and the plant with the lowest percentage of carbohydrate mass was P.indicus (211.15 percent). At 11 am, the compound-leaf plant S.mahogani (496.76 percent) had the largest percentage of carbohydrate mass, B.asiatica had the lowest (289.29 percent). B.asiatica had the most carbon dioxide absorption per leaf area per hour (g/leaf/hour), whereas S. mahogany had the lowest. S.mahogani (32.514 Å) had the highest chlorophyll concentration in the 06.00 am sample, while P.indicus had the highest chlorophyll concentration in the 11.00 am sample (42.440 Å).
... The C stored in the stem is the most important, especially at the post-anthesis stage because of its translocation from dry matter into the grain yield 9,10 . The natural capacity of crop growth being an important factor that affects CO 2 fixation per plant, any increase in CO 2 fixation by agricultural crops occurs through increase in dry weight of the biomass produced 11 . Therefore, a strategy of removing CO 2 from the atmosphere is to grow plants thereby sequestering CO 2 into biomass through photosynthesis, and converting it into SOC 12,13 . ...
... The net anthropogenic CO 2 emissions must be reduced to mitigate climate change. One of the solutions to mitigate climate change depends on conserving as much crop biomass as possible 11 . The large production of agricultural above-ground biomass not only offers an opportunity to mitigate anthropogenic climate change but also improves food security while improving the environment. ...
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This study was conducted to quantify the potential for CO2 fixation in the above-ground biomass of summer maize (Zea mays L.) under different tillage and residue retention treatments. The treatments were paired and included conventional tillage with straw removed (CT0), conventional tillage with straw retained (CTS), no-till with straw removed (NT0), no-till with straw retention (NTS), subsoiling with straw removed (SS0), and subsoiling with straw retained (SSS). The results indicated that NTS and SSS can enhance translocation of photosynthates to grains during the post-anthesis stage. SSS showed the highest total production (average of 7.8 Mg ha⁻¹), carbon absorption by crop (Cd) (average of 9.2 Mg C ha⁻¹), and total C absorption (Ct) (average of 40.4 Mg C ha⁻¹); and NTS showed the highest contribution of post-anthesis dry matter translocation to grain yield (average of 74%). Higher CO2 emission intensity and CO2 fixation efficiency (CFE) were observed for straw retention treatments. In comparison with CTS, the mean CFE (%) over four years increased by 26.3, 19.0, 16.5, and 9.4 for NT0, SS0, NTS, and SSS, respectively. Thus, SSS and NTS systems offer the best options for removing CO2 from the atmosphere while enhancing crop productivity of summer maize in the North China Plain.
... As shown in this Figure, the cultivation is mainly carried out on the available lands by 98.9%, and expanded on the barley and watermelon lands by 1.1%. According to the presented data (see tables B4 ( Carvajal, 2010, Kumara et al., 2016, Flores, 2016, and B5 in Appendix B ) the barely and the watermelon crops have the least penalty cost of land use change and the least absorbent of Co 2eq emissions among other crops. This indicates the correct behavior of the proposed model in reducing the total cost and the Co 2eq emissions. ...
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In this paper, efforts have been devoted in tune with the voices for rights of nature and the pursuit of replacing traditional fossil energy with renewable energy for a safer global environment. A two phase-approach to design a sustainable sugarcane-to-bioenergy supply chain network is developed. In the first phase, a hybrid Best-Worst (BWM) and Combinative Distance-Based Assessment (CODAS) method is utilized for finding the most suitable regions for sugarcane cultivation according to climatic, ecological and social criteria. In the second phase, a novel multi-objective mixed-integer linear programming (MOMILP) model is formulated considering the Water-Energy-Food-Land (WEFL) nexus. A hybrid solution method of augmented ɛ-constraint (AUGMECON) and CODAS method is finally developed to solve the model. This method is utilized for obtaining Pareto solutions of three-objective functions; profit, Co2-equivalent emissions (Co2eq emissions), and water consumption. To evaluate the efficiency of the developed methodology, a real case study in Iraq is applied. The results show that the sugarcane can be cultivated on the available arable land area by 98.9%.
... In the 13 C-experiment, 3.81 mol of 13 CO 2 were consumed which corresponds to a consumption rate of 11.5 mmol 13 CO 2 /g FW (Additional file 1: Equation (S1, S4)). The consumed amounts of 15 N or 13 CO 2 are in good agreement with the literature [29][30][31]. ...
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Background: Stable isotopically labelled organisms have found wide application in life science research including plant physiology, plant stress and defense as well as metabolism related sciences. Therefore, the reproducible production of plant material enriched with stable isotopes such as 13C and 15N is of considerable interest. A high degree of enrichment (> 96 atom %) with a uniformly distributed isotope (global labelling) is accomplished by a continuous substrate supply during plant growth/cultivation. In the case of plants, 13C-labelling can be achieved by growth in 13CO2(g) atmosphere while global 15N-labelling needs 15N- containing salts in the watering/nutrient solution. Here, we present a method for the preparation of 13C and 15N-labelled plants by the use of closed growth chambers and hydroponic nutrient supply. The method is exemplified with durum wheat. Results: In total, 330 g of globally 13C- and 295 g of 15N-labelled Triticum durum wheat was produced during 87 cultivation days. For this, a total of 3.88 mol of 13CO2(g) and 58 mmol of 15N were consumed. The degree of enrichment was determined by LC-HRMS and ranged between 96 and 98 atom % for 13C and 95-99 atom % for 15N, respectively. Additionally, the isotopically labelled plant extracts were successfully used for metabolome-wide internal standardisation of native T.durum plants. Application of an isotope-assisted LC-HRMS workflow enabled the detection of 652 truly wheat-derived metabolites out of which 143 contain N. Conclusion: A reproducible cultivation which makes use of climate chambers and hydroponics was successfully adapted to produce highly enriched, uniformly 13C- and 15N-labelled wheat. The obtained plant material is suitable to be used in all kinds of isotope-assisted research. The described technical equipment and protocol can easily be applied to other plants to produce 13C-enriched biological samples when the necessary specific adaptations e.g. temperature and light regime, as well as nutrient supply are considered. Additionally, the 15N-labelling method can also be carried out under regular glasshouse conditions without the need for customised atmosphere.
... In the 13 C-experiment, 3.81 mol of 13 CO 2 were consumed which corresponds to a consumption rate of 11.5 mmol 13 CO 2 /g FW (Additional file 1: equation (S1, S4)). The consumed amounts of 15 N or 13 CO 2 are in good agreement with the literature (29)(30)(31). ...
Preprint
Full-text available
Background Stable isotopically labelled organisms found wide application in life science research including plant physiology, plant stress and defense as well as metabolism related sciences. Therefore, the reproducible production of plant material enriched with stable isotopes such as 13 C and 15 N is of considerable interest. A high degree of enrichment (>96 atom%) with a uniformly distributed isotope (global labelling) is accomplished by a continuous substrate supply during plant growth/cultivation. In the case of plants, 13 C-labelling can be achieved by growth in 13 CO 2(g) atmosphere while global 15 N labelling needs 15 N- containing salts in the watering/nutrient solution. Here, we present a method for the preparation of 13 C and 15 N labelled plants by the use of closed growth chambers and hydroponic nutrient supply. The method is exemplified with durum wheat. Results In total, 330 g of globally 13 C- and 295 g of 15 N labelled T. durum wheat was produced during 87 cultivation days. For this, a total of 3.88 mol of 13 CO 2(g) and 58 mmol of 15 N were consumed. The degree of enrichment was determined by LC-HRMS and ranged between 96-98 atom% for 13 C and 95-99 atom% for 15 N, respectively. Additionally, the isotopically labelled plant extracts were successfully used for metabolome-wide internal standardisation of native T.durum plants. Application of an isotope-assisted LC-HRMS workflow enabled the detection of 652 truly wheat-derived metabolites out of which 143 contain N. Conclusion A reproducible cultivation which makes use of climate chambers and hydroponics was successfully adapted to produce highly enriched, uniformly 13 C- and 15 N-labelled wheat. The obtained plant material is suitable to be used in all kinds of isotope-assisted research. The described technical equipment and protocol can easily be applied to other plants to produce 13 C-enriched biological samples when the necessary specific adaptations e.g. temperature and light regime, as well as nutrient supply are considered. Additionally, the 15 N-labelling method can also be carried out under regular glasshouse conditions without the need for customised atmosphere.
... In the 13 C-experiment, 3.81 mol of 13 CO 2 were consumed which corresponds to a consumption rate of 11.5 mmol 13 CO 2 /g FW (Additional file 1: equation (S1, S4)). The consumed amounts of 15 N or 13 CO 2 are in good agreement with the literature (29)(30)(31). ...
Preprint
Full-text available
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... For the preferred wheat plants, thereto an average carbon content of 40.77 percent was assumed. The pea plants were considered instead with 41.93 percent carbon content, which has been set equal to the carbon content of broccoli (Carvajal 2010). Salicornia, in general, has a lower carbon binding, which is why only 25 percent carbon content were used for the plausibility check (Glenn et al. 1992). ...
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... For the preferred wheat plants, thereto an average carbon content of 40.77 percent was assumed. The pea plants were considered instead with 41.93 percent carbon content, which has been set equal to the carbon content of broccoli (Carvajal 2010). Salicornia, in general, has a lower carbon binding, which is why only 25 percent carbon content were used for the plausibility check (Glenn et al. 1992). ...
Book
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... By far, the greatest area of land -7.48 million ha -is occupied by cereal crops [40,41,[45][46][47]. According to the available data on CO 2 sequestration for Spain [48], wheat absorbs 13.9 t CO 2 /ha per year, while oat -11.7 t CO 2 /ha per year. However, sequestration in the climatic zone of Poland is less efficient. ...
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... They stated that approximately 100 kg of crude Karanja oil can be obtained from one hectare of plantation. Mota et al. [29] investigated CO 2 absorption for various crops, including orange oil, and concluded that 5.6 tons of CO 2 are absorbed by one hectare of plantation per year. Approximately 360 kg of orange oil is yielded from one hectare of orange trees. ...
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In the context of global change, attention has been focused on the increases in CO2 and temperature, as well as a reduction in the global solar irradiance. In this chapter we have explored how components of global change such as CO2, temperature and radiation will affect water uptake by plants. We focus on how aquaporins will respond to these environmental factors in order to maintain water balance in plants according to the water demand. Plant growth may be stimulated directly by increasing CO2 concentration, through enhanced photosynthesis, or, indirectly, through induced plant water consumption. However, the fine regulation of aquaporins, also involved in CO2 transport through membranes, will be crucial in the control of H2O and CO2 diffusion. Raised temperatures may benefit some crops but disadvantage others through increased evapotranspiration and thermal damage. However, in general, plants can develop different adaptive mechanisms in order to avoid water-deficit stress and excess transpiration modulating the hydraulic conductance, which involve the expression and activity of aquaporins. In the same way, the response of plants to the amount of perceived radiation affects water balance. Therefore, the study of aquaporin regulation is necessary for establishing future adaptation of plants to global change. KeywordsClimate change-CO2 -Water-Plant-Aquaporin-Temperature-Radiation
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On the basis of recent results with young primary maize roots, a model is proposed for the movement of water across roots. It is shown how the complex, 'composite anatomical structure' of roots results in a 'composite transport' of both water and solutes. Parallel apoplastic, symplastic and transcellular pathways play an important role during the passage of water across the different tissues. These are arranged in series within the root cylinder (epidermis, exodermis, central cortex, endodermis, pericycle stelar parenchyma, and tracheary elements). The contribution of these structures to the root's overall radial hydraulic resistance is examined. It is shown that as soon as early metaxylem vessels mature, the axial (longitudinal) hydraulic resistance within the xylem is usually not rate-limiting. According to the model, there is a rapid exchange of water between parallel radial pathways because, in contrast to solutes such as nutrient ions, water permeates cell membranes readily. The roles of apoplastic barriers (Casparian bands and suberin lamellae) in the root's endo- and exodermis are discussed. The model allows for special characteristics of roots such as a high hydraulic conductivity (water permeability) in the presence of a low permeability of nutrient ions once taken up into the stele by active processes. Low root reflection coefficients indicate some apoplastic by-passes for water within the root cylinder. For a given root, the model explains the large variability in the hydraulic resistance in terms of a dependence of hydraulic conductivity on the nature and intensity of the driving forces involved to move water. By switching the apoplastic path on or off, the model allows for a regulation of water uptake according to the demands from the shoot. At high rates of transpiration, the apoplastic path will be partially used and the hydraulic resistance of the root will be low, allowing for a rapid uptake of water. On the contrary, at low rates of transpiration such as during the night or during stress conditions (drought, high salinity, nutrient deprivation), the apoplastic path will be less used and the hydraulic resistance will be high. The role of water channels (aquaporins) in the transcellular path is in the fine adjustment of water flow or in the regulation of uptake in older, suberized parts of plant roots lacking a substantial apoplastic component. The composite transport model explains how plants are designed to optimize water uptake according to demands from the shoot and how external factors may influence water passage across roots.
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Antioxidants are believed to be important in the prevention of diseases such as cancer and cardiovascular disease. Lycopene is one of the main antioxidants to be found in fresh tomatoes and processed tomato products. The lycopene content also accounts for the redness of the fruit, which is one of the main qualities for which industry and consumers now look. Other carotenes (such as β-carotene), vitamin C, vitamin E and various phenolic compounds are also thought to be health-promoting factors with antioxidant properties. Since the antioxidant content of tomatoes may depend on genetic factors, the choice of variety cultivated may affect the results at harvest. To be able to control the antioxidant content of tomatoes at the field level when growing a given variety, it is necessary to know the effects of both environmental factors and the agricultural techniques used. Temperatures below 12 °C strongly inhibit lycopene biosynthesis and temperatures above 32 °C stop this process altogether. The effects of the temperature on the synthesis of other antioxidants have not yet been properly assessed. The effects of light have been studied more thoroughly, apart from those on vitamin E. The effects of water availability, mineral nutrients (nitrogen, phosphorus, potassium and calcium) and plant growth regulators have been studied, but results are sometimes contradictory and the data often incomplete. During the ripening period, lycopene content of tomatoes increases sharply from the pink stage onwards, but no sufficient attempts have been made so far to assess the changes in the other antioxidants present in the fruit. This paper reviews the present state of the art. Copyright © 2003 Society of Chemical Industry
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Agricultural practices can play an important role in atmospheric CO2 emission and fixation. In this study, we present results on carbon fluxes in the biomass of two typical Mediterranean orchards indicating that proper canopy management coupled with other agricultural techniques could increase the absorption of atmospheric CO2 and its storage. We also discuss the potential environmental contribution of the orchards to enhancement of both soil and air quality. Trials were carried out in southern Italy on olive (Olea europaea L.) and peach orchards (Prunus persica L.) at different age and plant densities. At the end of each vegetative season, values of fixed atmospheric CO2 were calculated by measuring dry matter accumulation and partitioning in the different plant organs. In the early years, sequestered CO2 was primarily distributed in the permanent structures and in the root system while in mature orchards the fixed CO2 was distributed in leaves, pruning materials and fruit. Significant differences in amounts of fixed CO2 were observed in peach orchards cultivated using different planting and training strategies. The results underline the importance of training system, plant density and cultivation techniques in the absorption of atmospheric CO2 and its storage as organic matter in the soil.
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Regulatory risk assessments are conducted prior to establishing allowable levels for pesticides on commodities. In the United States, the Environmental Protection Agency (EPA) is responsible for ensuring that consumer exposure to pesticides poses a “reasonable certainty of no harm” (Winter 2001). The Food Quality Protection Act requires that EPA consider the potential greater susceptibility and exposure of infants and children to pesticides via pesticide residues in food and water, residential pesticide use, and the cumulative effects of pesticide groups that share a common mechanism of toxicological activity. Generally, risks meeting the “reasonable certainty of no harm” standard occur when the lifetime cancer risk to pesticide exposure—using conservative (risk-enhancing) assumptions of cancer development—are below 1 excess cancer per 1 million persons exposed. For noncancer effects, a reasonable certainty of no harm occurs when exposure, either on an acute (short-term) or chronic (long-term) basis, is below the reference dose (RfD) 99.9% of the time. The RfD is not a toxicological threshold but is typically a derivative of finding the most sensitive toxicological effect observed in animal toxicology studies by determining the highest dose level that does not cause such an effect and dividing that level by a factor of 100 or more. If EPA is confident that the consumer risks from a pesticide represent a reasonable certainty of no harm, then it establishes tolerances at levels high enough to ensure that pesticide applications made in accordance with directions will not result in residues above tolerance levels (Winter 2001).
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Over the past decade, free-air CO2 enrichment (FACE) experiments have been conducted on wheat, perennial ryegrass, and rice, which are C3 grasses; sorghum, a C4 grass; white clover, a C3 legume; potato, a C3 forb with tuber storage; and cotton and grape, which are C3 woody perennials. Elevated CO2 increased photosynthesis, biomass, and yield substantially in C3 species, but little in C4. It decreased stomatal conductance in both C3 and C4 species and greatly improved water-use efficiency in all crops. Growth stimulations were as large or larger under water stress compared to well-watered conditions. At low soil N,stimulations of nonlegumes were reduced, whereas elevated CO2 strongly stimulated the growth of the clover legume at both ample and low N conditions. Roots were generally stimulated more than shoots. Woody perennials had larger growth responses to elevated CO2, but their reductions in stomatal conductance were smaller. Tissue N concentrations went down, while carbohydrate and some other carbon-based compounds went up, with leaves being the organs affected most. Phenology was accelerated slightly in most but not all species. Elevated CO2 affected some soil microbes greatly but not others, yet overall activity was stimulated. Detection of statistically significant changes in soil organic carbon in any one study was nearly impossible, yet combining results from several sites and years, it appeared that elevated CO2 did increase sequestration of soil carbon. Comparisons of the FACE results with those from earlier chamber-based results were consistent, which gives confidence that conclusions drawn from both types of data are accurate.
Article
Maize grain yield and response to N (0, 50, and 100 kg ha−1) and P fertilization (0, 15, and 30 kg ha−1) were determined for fields differing in history of organic inputs of four farmers in the Sudan savanna zone of northern Togo over a period of 3 years. Each farmer selected a field that had benefited from long-term organic inputs close to his family homestead (‘infield’) and another field receiving considerably less or no organic inputs (‘outfield’). Soil organic C content was 13.4 g kg−1 for infields and 6.3 g kg−1 for outfields. Maize yields on infields were consistently 1.0–1.5 t ha−1 higher than on outfields with and without fertilizer. N was the major limiting yield nutrient in this study. Phosphorus had only a minor, and in most cases, non-significant effect. Average recovery fractions of applied N fertilizer (RFN) were significantly (p = 0.01) higher on infields compared to outfields over 3 years (0.41 kg kg−1 versus 0.33 kg kg−1). However, the agronomic efficiency of applied N (AEN) was similar over three years (19.0 kg grain kg−1 N). The greatest differences between outfields and infields were observed in 2001, due to low and erratic rainfall. In that year, gains of infields over outfields were highly significant in terms of maize yield (from 0.8 to 2.0 t ha−1), RFN (from 0.21 to 0.33 kg kg−1), and AEN (from 9.4 to 14.4 kg grain kg−1 N). Highest N recovery rates were consistently obtained on infields using 50 kg N and 15 kg P ha−1. Results indicate that judicious use of mineral fertilizer (i.e., taking into account the indigenous soil nutrient supplying capacity and targeting yield levels below 80% of climate-determined yield) should be promoted on relatively fertile infields rather than on poorer outfields. This strategy would lead to reduced production risk in years with low rainfall, higher fertilizer recovery, and increased productivity.