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Improving water use efficiency for rainfed agriculture

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Wei Qin

on 17 March 2014

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Transcript of Improving water use efficiency for rainfed agriculture

Stomatal conductance
1. AquaCrop is designed for herbaceous crops but not yet available for fruit trees;

2. Coupling with other model, e.g. FUSSIM, may be possible, depending on research objectives ... ;

3. Opportunities and challenges ahead, look forwards to cooperations.
Improving water use efficiency for rainfed agriculture
Wei Qin

Wageningen University and Research Centre
500 pages

50% herbaceous crops

50% fruit trees

1. AquaCrop is a novel water driven crop model.

2. Requires small number of input data and parameters.

3. Balance simplicity, accuracy and robustness.
Wei Qin

Wageningen University & Research Centre
Increasing water use efficiency in rainfed agriculture
FAO AquaCrop Model
A water-driven model

Requires small number of parameters

Accuracy, simplicity and robustness
Steduto et al., (2009); Todorovic et al., (2009); Crop yield response to water (2012) FAO irrigation and drainage papers No.66
How does AquaCrop work?
Yx and Ya are the maximum and actual yield
ETx and ETa are the maximum and actual ET
Ky is the proportionality factor
Yield response to water (1979) FAO irrigation and drainage papers No.33
(Steduto et al., 2009)
I, irrigation;
Tn, minimum air temperature;
Tx, Max air temperature;
ETo, reference ET;
E, soil evaporation;
Tr, canopy transpiration;
gs, stomatal conductance;
WP, water productivity;
HI, harvest index;
CO2, atmospheric concentration;
(1)-(4), water stress responses
Yield as function of ET
Biomass as function of Tr
WP is the water productivity
(biomass per unit of cumulative transpiration)
(de Wit, 1958; Hanks, 1983; Tanner and Sinclair, 1983)
Separating ET into crop transpiration (Tr) and soil evaporation (E)
Normalized WP*
WP* is the normalized water productivity
(Steduto et al., 2007)
Use canopy cover(CC) instead of LAI
CCo and CCx are the initial and maximum green canopy cover
CGC is the green canopy growth coefficient
CDC is the green canopy decline coefficient
1)Water limited yield therefore led to Low WUE.

2) Although water is limited, only 1/3 of water use by plant. The rest was loss by evaporation (60% in fallow season).

3)WUE could be doubled by decreasing evaporation via low cost measures.
1. Climate
2. Crop
3. Soil
4. Field management
Large rainfed agricultural area
95% in sub-Saharan Africa
90% in Latin America
75% in the Middle East and North Africa
65% in East Asia
60% in South Asia
FAOSTAT (2005)
Methods & Materials
1980 - 2010
AquaCrop Model
Research gap
Short-term VS long-term

Growing season VS fallow season

Why rainfed agriculture
Low productivity


1. Quantify water cycle for both crop growing and fallow season

2. Understand relationship between yield and water use

3. Explore options for improving water use efficiency
Monthly rainfall
Soil water change in time
Water balance
Relationships between yield and water use
Potential for improvements
Soil water change in space
Total water = 1,386,000,000 km3

Fresh water = 10,530,000 km3 (<1%)
7 billion in 2013

9 billion in 2050
Wheat VS Orange
1. Calibrate model with long-term monitored rainfed wheat

2. Quantify water balance (separate E and T)

3. Understand relationships between crop yield and water use
Using AquaCrop in our research
1. AquaCrop: rationale

2. AquaCrop: application

3. Possibilities in coupling of FUSSIM

1. Crop processes, production
2. Soil water balance
3. Irrigation requirement
4. Soil salinity
Figure 1. Monthly rainfall and available soil water (1980 - 2010).
Figure 3. Performance of the model.
Figure 2. Soil water change in 2 meter's profile.
Figure 4. Water balance (rainfall, change in soil water, E, T) of the total season (A), growing season (B) and fallow season (C).
Figure 5. Relationships between yield and water use.
Figure 6. Model experiments on improving yield (A) and WUE (B).
1. Low yield and WUE were due to limited water and poor sync with rain season.

2. Winter wheat used only 1/3 of water; 2/3 was lost by evaporation.

3. Large potential for improving yield and WUE in rainfed winter wheat.
Rainfed agriculture in China
1. No irrigation water

2. Low crop productivity

3. Poverty

Materials & Methods
Region: The Loess Plateau

Crop: winter wheat (1980-2010)

Model: FAO AquaCrop
Hi, Wei, can you give a talk in Beijing?
Do I have to say YES?
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