A meta-analysis of global crop water productivity of three leading world crops(wheat,corn,and rice)in the irrigated areas over three decades

The overarching goal of this study was to perform a comprehensive metaanalysis of irrigated agricultural Crop Water Productivity(CWP)of the world’s three leading crops:wheat,corn,and rice based on three decades of remote sensing and non-remote sensing-based studies.Overall,CWP data from 148 crop growing study sites(60 wheat,43 corn,and 45 rice)spread across the world were gathered from published articles spanning 31 different countries.There was overwhelming evidence of a significant increase in CWP with an increase in latitude for predominately northern hemisphere datasets.For example,corn grown in latitude 40–50°had much higher mean CWP(2.45 kg/m^(3))compared to mean CWP of corn grown in other latitudes such as 30–40°(1.67 kg/m^(3))or 20–30°(0.94 kg/m^(3)).The same trend existed for wheat and rice as well.For soils,none of the CWP values,for any of the three crops,were statistically different.However,mean CWP in higher latitudes for the same soil was significantly higher than the mean CWP for the same soil in lower latitudes.This applied for all three crops studied.For wheat,the global CWP categories were low(≤0.75 kg/m^(3)),medium(>0.75 to<1.10 kg/m^(3)),and high CWP(≥1.10 kg/m^(3)).For corn the global CWP categories were low(≤1.25 kg/m^(3)),medium(>1.25 to≤1.75 kg/m^(3)),and high(>1.75 kg/m^(3)).For rice the global CWP categories were low(≤0.70 kg/m^(3)),medium(>0.70 to≤1.25 kg/m^(3)),and high(>1.25 kg/m^(3)).USA and China are the only two countries that have consistently high CWP for wheat,corn,and rice.Australia and India have medium CWP for wheat and rice.India’s corn,however,has low CWP.Egypt,Turkey,Netherlands,Mexico,and Israel have high CWP for wheat.Romania,Argentina,and Hungary have high CWP for corn,and Philippines has high CWP for rice.All other countries have either low or medium CWP for all three crops.Based on data in this study,the highest consumers of water for crop production also have the most potential for water savings.These countries are USA,India,and China for wheat;USA,China,and Brazil for corn;India,China,and Pakistan for rice.For example,even just a 10%increase in CWP of wheat grown in India can save 6974 billion liters of water.This is equivalent to creating 6974 lakes each of 100 m^(3)in volume that leads to many benefits such as acting as‘water banks’for lean season,recreation,and numerous ecological services.This study establishes the volume of water that can be saved for each crop in each country when there is an increase in CWP by 10%,20%,and 30%.

Remote sensing monitoring on regional crop water productivity in the Haihe River Basin

Crop water productivity （CWP） agricultural development in water scarcity is one of the important indicators for sustainable area. There is serious conflict between water sup- ply and requirement in the Haihe River Basin. CWP of winter wheat and summer maize from 2003 to 2007 in the Haihe River Basin is estimated based on large-scale evapotranspiration （ET） and crop yield obtained by remote sensing technology. Spatial and temporal distribution of CWP of winter wheat and summer maize is investigated in this study. Results show that CWP of winter wheat in most parts of the study area varies from 1.02 kg/m3 to 1.53 kg/m3, and CWP of summer maize varies from 1.31 kg/m3 to 2.03 kg/m3. Multi-year averaged CWP of winter wheat and summer maize in the study area is about 1.19 kg/m3 and 1.59 kg/m3. CWP results show certain promotion potential to alleviate the water shortage in the Haihe River Basin. Correlation analysis of CWP, crop yield and ET shows that there is great potential for crop yield promotion without the growth in irrigation water. Large-scale CWP estimated by remote sensing technology in this study shows spatial distribution features, which could be used to real-time agricultural water resource management combined with crop yield and ET.

LINKING CROP WATER PRODUCTIVITY TO SOIL PHYSICAL,CHEMICAL AND MICROBIAL PROPERTIES

Agriculture uses a large proportion of global and regional water resources.Due to the rapid increase of population in the world,the increasing competition for water resources has led to an urgent need in increasing crop water productivity for agricultural sustainability.As the medium for crop growth,soils and their properties are important in affecting crop water productivity.This review examines the effects of soil physical,chemical,and microbial properties on crop water productivity and the quantitative relationships between them.A comprehensive view of these relationships may provide important insights for soil and water management in arable land for agriculture in the future.

Effects of different irrigation frequencies and incorporation of rice straw on yield and water productivity of wheat crop

The current rapid increase in irrigation water consumption is considered unsustainable and threatens the world food production.Therefore,it is mandatory to promote modern techniques and to manage existing conventional irrigation methods.The present study was attempted to determine the effects of different irrigation frequencies and rice straw incorporation rates on yield and water productivity of the wheat crop.The experiment was arranged with randomize complete block design involving nine treatments(RS 0 I 7,RS 0 I 15,RS 0 I 22,RS 1 I 7,RS 1 I 15,RS 1 I 22,RS 2 I 7,RS 2 I 15 and RS 2 I 22)under three replications.Results exposed that the incorporation of rice straw with different irrigation frequencies significantly improved physico-chemical properties of soil.Moreover,soil bulk density,infiltration rate,pH,electrical conductivity significantly decreased and soil porosity significantly increased under all treatments.Furthermore,maximum crop yield and crop water productivity of 7706.4 kg/hm 2 and 1.92 kg/m 3 respectively were found under RS 1 I 15 treatment.Based on experimental results it can be concluded that irrigation frequency and incorporation of rice straw had significant effects on the physico-chemical properties of soil,total grain yield and water productivity of the wheat crop.However,this study suggested that the wheat crop yield and water productivity could be increased by incorporating 1 t/hm 2 rice straw with 15 d of irrigation frequency.

PRODUCTIVITY AND WATER UTILITY FOR MAIN CROPS IN LOESSAL HILL.REGION, SOUTHERN NINGXIA

The loessal hill region in southern Ningxia is a semiarid and severe eroded area with developed agriculture and animal husbandry. It has long been an argument whether there might be more potentiality of farming and whether food production can be sustained at a level of local sufficiency.

Annual Rainfall and Dryland Cotton Lint Yield—Southern High Plains of Texas

Agriculture in the Texas High Plains (THP) is in a transition phase of producing crops with a diminishing supply of irrigation-water from the Ogallala aquifer to dryland production systems. This shift is driven by the fact that the depth to the water table of the Ogallala aquifer continues to increase. Dryland cotton production systems are prevalent in the southern counties of the THP and our purpose was to use the long-term dryland cotton lint yields from these counties as precursors of the future cotton production patterns that will emerge in this region. For this purpose, from 1972 to 2018, we calculated the ratio of dryland cotton lint yield per unit of annual rainfall at the county level. This ratio is called crop water productivity (CWP) and has units of mass per unit volume (g/m3). In our analysis, we used cotton lint yield data provided by the National Agricultural Statistics and rainfall data provided by the National Oceanic and Atmospheric Administration. Our results indicated that the three datasets used in our analysis, i.e., cotton lint yield, rainfall and CWP were all normally distributed. In this time period, 1972 to 2018, only one year 2011—a year with a record drought of 179 mm of rain failed to produce a dryland cotton crop in all the counties used in our analysis. The mean cotton lint yield ± standard deviation ranged from a high of 400 ± 175 kg/ha in Lubbock County to a low of 252 ± 144 kg/ha in Andrews County. However, the counties with the largest CWP > 90 g/m3 were Glasscock, Midland and Martin County. The importance of this result is that these counties are in the southern region of the THP and are subject to extreme environmental conditions and yet cotton producers manage to produce a cotton crop in most years. We conclude that management production methods used by these dryland producers represent the future schemes that will need to be adopted in other counties to sustain the emerging dryland cropping systems across the THP.