Increasing Crop Water Productivity Research Articles

INNOVATIONS IN IRRIGATION SYSTEMS IN AFRICA†

INNOVATIONS IN IRRIGATION SYSTEMS IN AFRICA^†

Global Water Security: Current Research and Priorities for Action

HighlightsWe provide context and perspectives on 13 articles in the Global Water Security collection.Limited irrigation, precision irrigation, and sustainable water resources management were critical themes.The collection emphasizes the need for adopting location-specific technologies to achieve global water security.Advances in data acquisition, data analysis, and modeling should be utilized to aid managing water resources. Abstract. This article introduces the Global Water Security collection in this issue of Transactions of the ASABE and issue 36(1) of Applied Engineering in Agriculture. Researchers, educators, industry partners, agricultural producers, and policymakers from 19 countries met at Hyderabad, India, to discuss critical issues and advancements at the Global Water Security Conference for Agriculture and Natural Resources. The conference was organized jointly by ASABE and the Indian Society of Agricultural Engineers (ISAE). This special collection consists of 13 articles selected from the 245 meeting presentations as well as invited articles. A perspectives article in this collection summarizes seven key priorities identified for action at the conference: reduce food waste, increase wastewater reuse, increase agricultural resiliency and efficiency, optimize irrigation efficiency and increase crop water productivity, improve water supply management, improve water resource infrastructure, and enhance water resource decision-making and policy formulation. The remaining 12 articles address a wide range of water security topics grouped by four themes: sustainable management of water resources (3 articles), limited irrigation for water conservation (5 articles), precision irrigation management (2 articles), and water management in hilly regions (2 articles). While these articles are not inclusive of all water security challenges in the agriculture and natural resources sectors, they highlight selected important challenges and potential solutions. The research presented in this special collection emphasizes the importance of developing and using appropriate location-specific technologies that increase water application efficiency and water use efficiency while maintaining adequate water supplies for natural resource functions and ecosystem services to ensure global water security. Keywords: Climate change, Crop water productivity, Food security, Irrigation efficiency, Natural resource policy, Wastewater reuse, Water resource infrastructure, Water scarcity.

Review: Climate change and the water footprint of wheat production in Zimbabwe

Reductions in the water footprint (WF) of crop production, that is, increasing crop water productivity (CWP), is touted as a universal panacea to meet future food demands in the context of global water scarcity. However, efforts to reduce the WF of crop production may be curtailed by the effects of climate change. This study reviewed the impacts of climate change on the WF of wheat production in Zimbabwe with the aim of identifying research gaps. Results of the review revealed limited local studies on the impacts of climate change on the WF of wheat production within Zimbabwe. Despite this, relevant global and regional studies suggest that climate change will likely result in a higher WF in Zimbabwe as well as at the global and regional level. These impacts will be due to reductions in wheat yields and increases in crop water requirements due to high temperatures, despite the CO2 fertilization effect. The implications of a higher WF of wheat production under future climate change scenarios in Zimbabwe may not be sustainable given the semi-arid status of the country. The study reviewed crop-level climate change adaptation strategies that might be implemented to lower the WF of wheat production in Zimbabwe.

Water accounting for conjunctive groundwater and surface water irrigation sources: A case study in the middle Heihe River Basin of arid northwestern China

Oases in arid northwestern China play a significant role in the region’s economic stability and development. Overexploitation of the region’s water resources has led to serious environmental consequences. In oases, irrigated agriculture is the primary consumer of water, but water shortages resulting from dramatically growing human needs have become a bottleneck for regional sustainable development, making effective management of the limited available water critical. Effective strategies must be formulated to increase agricultural productivity while reducing its environmental impacts. To support the development of such strategies, water use patterns were analyzed during the 2007 and 2008 growing seasons, from May to early October, to identify opportunities for improving water management using the Molden-Sakthivadivel water-accounting method, which combines groundwater and surface water into a single domain and can provide a good estimate of the uses, depletion, and productivity of water in a water basin context. The study area lies in Linze County, Gansu Province, China. In the study area, the inflow water resources consist of irrigation, precipitation, and soil water, which accounted for 89.3%, 8.9%, and 1.8% of the total in 2007, and 89.3%, 4.8%, and 5.9% in 2008, respectively. The irrigation depends heavily on groundwater, which accounted for 82.1% and 83.6% of the total irrigation water in 2007 and 2008, respectively. In 2007 and 2008, deep percolation accounted for 50.1% and 47.9% of the water outflow, respectively, with corresponding depleted fractions of 0.51 and 0.55, respectively. For the irrigation district as a whole, the water productivity was only 1.37 CNY/m3. To significantly increase crop water productivity and prevent depletion of the region’s groundwater aquifer, it will be necessary to reduce the amount of water used for irrigation. Several water-saving agricultural practices are discussed and recommended.

Estimating Changes in the Green Water Productivity of Cropping Systems in Northern Shaanxi Province in China’s Loess Plateau

Water shortages limit agricultural production in the world’s arid and semi-arid regions. The Northern region of China’s Shaanxi Province, in the Loess Plateau, is a good example. Raising the water productivity of rainfed grain production in this region is essential to increase food production and reduce poverty, thereby improving food security. To support efforts to increase crop water productivity (CWP), we accounted for limitations of most existing studies (experimental studies of specific crops or hydrological modeling approaches) by using actual field data derived from statistical reports of cropping patterns. We estimated the CWPs of nine primary crops grown in four counties in Northern Shaanxi from 1994 to 2008 by combining statistics on the cultivated area and yields with detailed estimates of evapotranspiration based on daily meteorological data. We further calculated both the caloric CWP of water (CCWP) and the CWP of productive water (i.e., water used for transpiration). We found that regional CWP averaged 6.333 kg mm–1 ha–1, the CCWP was 17,683.81 cal mm–1 ha–1, the CWP of productive green water was 8.837 kg mm–1 ha–1, and the CCWP of productive green water was 24,769.07 cal mm–1 ha–1. Corn, sorghum, and buckwheat had the highest CWP, and although potatoes had the largest planted area and relatively high CWP, they had a low CCWP.

Future crop yields and water productivity changes for Nebraska rainfed and irrigated crops

ABSTRACT We assessed future rainfed and irrigated crop yield and water productivity changes in Nebraska across multiple climate and emission scenarios using an empirical modeling approach. We found rainfed crops showed slightly increased crop water productivity while irrigated crops showed no change or decreased water productivity. Contrary to U.S.-wide studies reporting declines in crop yields, we projected Nebraska crop yields to increase overall with greatest increases in current rainfed fields due to combined effects from maximum and minimum temperatures. However, the increased rainfed yields are not sufficient to fully close the gap between rainfed and irrigated yields. Abbreviations: USDA: U.S. Department of Agriculture; RegCM4.3: ICTP Regional Climate Model version 4.3; NCEP: National Centers for Environmental prediction; DOE: U.S. Department of Energy; CGCM: Canadian Climate Centre general circulation model; GFDL: Geophysical Fluid Dynamics Laboratory general circulation model; CRCM: Canadian Climate Centre regional climate model; CCSM: National Center for Atmospheric Research general circulation model; HRM3: Hadley Centre’s Regional Model 3; HADCM3: Hadley Centre’s general circulation model; WRFG: the NCAR Weather Research and Forecasting model; CCCma: Canadian Centre for Climate Modelling and Analysis; CanESM2: Canadian Centre Earth System Model 2; ICHEC-EC: A European community Earth-System Model; IPCC: Intergovernmental Panel on Climate Change; RMSE: Root Mean Square Error

Effects of tillage, mulching and N management on yield, water productivity, N uptake and residual soil nitrate in a long-term wheat-summer maize cropping system

A thorough understanding of coupled effects of soil management (tillage), mulch and N rate on the wheat-maize system is crucial for achieving sustainable agriculture in the southern Loess Plateau of China. This study was based on a 12-year (2003–2015) field experiment and aimed to evaluate the impact of three wheat-maize systems (S) which varied in terms of tillage, mulch, wheat row spacing and irrigation management (CT, conventional tillage with no mulch; RFM, ridge-furrow with plastic film-mulched ridges and straw-mulched furrows; CTM, conventional tillage with straw mulch) combined with N fertilizer rates (0, 120 and 240kgNha−1) on crop yield, water productivity (WP, kg grain per kg of water input), N uptake, residual soil nitrate (RSN) and soil physicochemical properties. Results demonstrated that RFM significantly increased maize yield in comparison with CT in all 12 years, while CTM increased yield in comparison with CT from year 3 onwards. By contrast, wheat yield was not strongly influenced by RFM and CTM from 2004 to 2012 (except for 2008). Maize yields of RFM were significantly higher than those of CTM from the third year onwards. Compared with CT, the other two practices, and more so RFM, showed beneficial effects on crop yield, the amount of stored water, WP, N uptake and RSN. N fertilization significantly increased crop yield, WP and N uptake, while no significant difference was observed between the N120 and N240 treatments. Notably, considerable buildup of RSN to∼490kgNha−1 at maize harvest and ∼340kgNha−1 at wheat harvest were observed in 0–200cm soil depth when 240kgNha−1 was applied. These results suggest that the conventional N rate of 240kgNha−1 is excessive, and risks serious contamination of the groundwater as a result of NO3−-N leaching. The N120 treatment was characterized with considerably lower RSN accumulation after harvest, while maintaining crop yield. Thus, we concluded that the RFM practice with 120kgNha−1 application could reduce irrigation water and fertilizer inputs and increase crop land and water productivity, and is a promising strategy for developing sustainable agriculture in the southern Loess Plateau and other areas with similar climate and cropping systems.

Plant-Based Methods for Irrigation Scheduling of Woody Crops

The increasing world population and expected climate scenarios impel the agricultural sector towards a more efficient use of water. The scientific community is responding to that challenge by developing a variety of methods and technologies to increase crop water productivity. Precision irrigation is intended to achieve that purpose, through the wise choice of the irrigation system, the irrigation strategy, the method to schedule irrigation, and the production target. In this review, the relevance of precision irrigation for a rational use of water in agriculture, and methods related to the use of plant-based measurements for both the assessment of plant water stress and irrigation scheduling, are considered. These include non-automated, conventional methods based on manual records of plant water status and gas exchange, and automated methods where the related variable is recorded continuously and automatically. Thus, the use of methodologies based on the Scholander chamber and portable gas analysers, as well as those of systems for measuring sap flow, stem diameter variation and leaf turgor pressure, are reviewed. Other methods less used but with a potential to improve irrigation are also considered. These include those based on measurements related to the stem and leaf water content, and to changes in electrical potential within the plant. The use of measurements related to canopy temperature, both for direct assessment of water stress and for defining zones with different irrigation requirements, is also addressed. Finally, the importance of choosing the production target wisely, and the need for economic analyses to obtain maximum benefit of the technology related to precision irrigation, are outlined.

Crop evapotranspiration calculation using infrared thermometers aboard center pivots

Irrigation scheduling using remotely sensed surface temperature can result in equal or greater crop yield and crop water use efficiency compared with irrigation scheduling using in-situ soil water profile measurements. Crop evapotranspiration (ETc) is useful for irrigation scheduling, and can be calculated using surface temperature. Recent advances in wireless infrared thermometers (IRTs) have made surface temperature measurement a viable alternative to in-situ soil water profile measurements, and wireless IRTs are practical for deployment aboard moving irrigation systems, such as center pivots. However, ETc calculation has not been tested using IRTs aboard center pivots in conjunction with recent advances in a two-source energy balance (TSEB) model. We compared daily ETc calculated by a TSEB model to daily ETc estimated by a simple soil water balance (SSWB), where the SSWB used volumetric soil water measured by a field calibrated neutron probe to the 2.4-m depth. Crops included two seasons each of corn (Zea mays L.), cotton (Gossypium hirsutum L.), and grain sorghum (Sorghum bicolor L.) at Bushland, Texas, USA. Discrepancies of TSEB vs. SSWB daily ETc were similar for each crop and season, and had root mean squared error from 1.5 to 1.8mm per day, mean absolute error from 1.1 to 1.5mm per day, and mean bias error from −0.51 to 0.63mm per day. A sensitivity analysis was conducted for daily evaporation (E), daily transpiration (T), and ETc calculated by the TSEB model. These were most sensitive to radiometric surface temperature, air temperature, the reference temperature used in time scaling (i.e., to convert instantaneous to daily E, T, and ETc), and incoming solar irradiance. Because over half of the irrigated area in the USA is now by center pivot, ETc calculated using IRTs aboard center pivots will be useful to maintain or increase crop water productivity.

Yield and Soil Water in Three Dryland Wheat and Grain Sorghum Rotations

Core Ideas Grain yield of the second wheat crop was 80% of first wheat crop in WWSF. Grain yield of the second sorghum crop was 63% of first sorghum crop in WSSF. Four‐year rotations were similar in productivity to 3‐yr WSF. Water productivity was greater with 4‐yr rotations than continuous wheat. Continuous no‐till did not increase second year wheat and sorghum yields. Diverse crop rotations sustain crop productivity by increasing crop water productivity and improving soil structure. The objective of this study was to compare two 4‐yr winter wheat (Triticum aestivum L.) and grain sorghum (Sorghum bicolor L.) rotations in terms of grain yield, available soil water, and water productivity along with continuous winter wheat. A field study was conducted from 1996 through 2015 on a deep silt loam soil near Tribune, KS. The study consisted of three crop rotations: continuous annual wheat (WW), wheat–wheat–sorghum–fallow (WWSF), and wheat–sorghum–sorghum–fallow (WSSF). Grain yield, biomass, water productivity, and soil water were all greater for sorghum after wheat compared with sorghum after sorghum. Similarly, grain yield, biomass, water productivity, and soil water were all greater for wheat after fallow compared with wheat after wheat. The yield of the second wheat crop was 80% of the first wheat crop in WWSF, whereas the yield of a second sorghum was only 63% of the first sorghum crop in WSSF. The average crop water productivity (7 kg ha−1 mm−1) of the WSSF rotation was greater than the other rotations. On average, the WSSF system produced 2.05 Mg ha−1 yr−1 wheat equivalent yield (WEY), which was similar to the 1.96 Mg ha−1 yr−1 WEY from the WWSF rotation and greater than WW, which produced 1.53 Mg ha−1 yr−1 of wheat grain. A WSF rotation would have produced 2.0 Mg ha−1 yr−1 WEY, so the 4‐yr rotations were not more productive than a 3‐yr WSF rotation.

Response of AquaCrop Model to Different Irrigation Schedules for Irrigated Cabbage

Agricultural sector faces the challenge to produce more food with less water by increasing crop water productivity. As such, the question of improving the present level of crop water productivity in general and for irrigation in particular assumes a great significance in perspective water resource planning. This study was undertaken to improve water productivity, i.e., ‘more crop per drop.’ In this study response of cabbage to different irrigation schedules under mulch and non-mulch condition using calibrated AquaCrop model was evaluated. AquaCrop is a crop model that simulates yield response to water developed by FAO and is appropriate to consider effects where water is the limiting factor for crop production. AquaCrop was calibrated for cabbage (Brassica oleracea var. capitata), a leafy vegetable. Simulations were carried out for the period November 27, 2013, to February 19, 2014 with T1, T2, T3 (treatments irrigation scheduling at 50 % moisture depletion of available water capacity under black, silver, and no polyethylene mulch with drip irrigation) and T4, T5, T6 (irrigation scheduling at 100 % evapotranspiration under black, silver, and no polyethylene mulch with drip irrigation). The model provided excellent simulation of canopy and yield. The harvest index was observed as 80 % for cabbage. Formulated Schedule with S1, S2, S3, S4, and S5 (irrigation schedule at 110, 90, 80, 70, and 60 % ETc) and S6, S7, S8, S9, and S10 (mulch + Irrigation schedule at 110, 90, 80, 70 and 60 % ETc). S8 saved 25.19 % water with only 4.63 % reduction in the yield of cabbage head compared to control and resulted in water use efficiency as 6.05 kg m−3. Thus S8 is recommended to be used for cabbage production, to water productivity.

A comprehensive analysis of blue water scarcity from the production, consumption, and water transfer perspectives

The issue of growing water scarcity has been increasingly perceived as a global systemic risk. To solve it, an integrated approach considering different perspectives of water scarcity is at a premise. In this study, we developed an approach to calculate the blue water scarcity (BWS) and integrated the production, consumption, and water transfer perspectives into a single framework. The results are as follows: The average BWS in the Hetao irrigation district was 0.491 during the 2001–2010 year period, which was much larger than the threshold of 0.30, indicating a high water stress level. From the production perspective, the agricultural sector was the largest contributor to regional water scarcity and the average BWS was as high as 0.479. From the consumption perspective, BWS related to virtual water export was much larger than that related to water consumption for making products to be consumed locally and the values were 0.422 and 0.069, respectively. Under the influence of physical and virtual water transfer, BWS changed from 0.242 (medium to high water stress level) to 0.491 (high water stress level). Strategies for reducing agricultural water consumption, such as increasing crop water productivity, improving irrigation efficiency, and promoting more reasonable irrigation water price, could be adopted in the Hetao irrigation district to alleviate regional BWS. Compared with physical and virtual water import, the virtual water export played a more important role in influencing the regional water scarcity, and the increase in crop water productivity, decrease in crop export volume, or adjustment of trade pattern from water-intensive crops to water-extensive ones could be feasible measures to decrease virtual water export for lower water stress, while the trade-offs in the product-consuming regions should be considered.

Improving Water Sustainability and Food Security through Increased Crop Water Productivity in Malawi

Agriculture accounts for most of the renewable freshwater resource withdrawals in Malawi, yet food insecurity and water scarcity remain as major challenges. Despite Malawi’s vast water resources, climate change, coupled with increasing population and urbanisation are contributing to increasing water scarcity. Improving crop water productivity has been identified as a possible solution to water and food insecurity, by producing more food with less water, that is, to produce “more crop per drop”. This study evaluated crop water productivity from 2000 to 2013 by assessing crop evapotranspiration, crop production and agricultural gross domestic product (Ag GDP) contribution for Malawi. Improvements in crop water productivity were evidenced through improved crop production and productivity. These improvements were supported by increased irrigated area, along with improved agronomic practices. Crop water productivity increased by 33% overall from 2000 to 2013, resulting in an increase in maize production from 1.2 million metric tons to 3.6 million metric tons, translating to an average food surplus of 1.1 million metric tons. These developments have contributed to sustainable improved food and nutrition security in Malawi, which also avails more water for ecosystem functions and other competing economic sectors.

Advances in a Two-Source Energy Balance Model: Partitioning of Evaporation and Transpiration for Cotton

Abstract. Accurate partitioning of the evaporation (E) and transpiration (T) components of evapotranspiration (ET) in remote sensing models is important for evaluating strategies aimed at increasing crop water productivity. A two-source energy balance (TSEB) model designed for row crops solves the energy balance of the soil-canopy-atmosphere continuum using surface brightness temperature. By solving the energy balance of the soil and plant canopy separately, the TSEB model can calculate E and T, which cannot be done with single-source models. However, few studies have tested the TSEB model where E or T measurements were available, which until recently has impeded its advance. This article reviews recent physically based advances of the TSEB model. The advances were tested using measurements of E, T, and ET by microlysimeters, sap flow gauges, and weighing lysimeters, respectively, at Bushland, Texas, for irrigated cotton having a wide range of canopy cover. Root mean square error (RMSE) and mean bias error (MBE) were 0.54 and -0.19 mm d-1, respectively, between measured and calculated E. RMSE and MBE were 0.87 and 0.31 mm d-1, respectively, between measured and calculated T. This was deemed an improvement over previous TSEB model versions, which overestimated E and underestimate T, resulting in RMSE and MBE of up to 3.8 and -3.5 mm d-1, respectively. Ongoing research includes testing the TSEB model using different remote sensing platforms, from ground-based to satellite scales.

Blue Water Demand for Sustainable Intensification

The agricultural challenge of meeting global food demand requires an increase in the level of agricultural water productivity and some increases in global water use. But many arid or semiarid agricultural regions of the world are facing declining water availability for irrigation. Examples of declining groundwater availability are seen throughout arid and semiarid areas of North America, Africa, and Asia. Relevant to water demand for sustainable intensification of agriculture, this paper touches on concepts where policy can work toward improving water productivity, including: (i) assessing crop water use and productivity, (ii) promoting cultural practices for increasing crop water productivity, (iii) improving efficiency of green water use, and (iv) protecting agricultural water supplies. Developing a paradigm of assessing crop water productivity and comparing with potential water‐limited yields is a valuable diagnostic tool leading to improved management and water use. Similarly, water footprinting is a water accounting tool that should be applied toward improvements in agricultural water productivity. These assessment tools can prioritize how and when agronomic practices and plant genetic improvements can best be employed. This paper also overviews some cultural practices that can improve water productivity in dryland, rainfed, and irrigated systems. Several examples of policies that influence the supply of water for irrigation are given. Innovative policy structures are needed that allow sharing of water among agricultural, municipal, and environmental users while also rewarding conservation and efficient use. Specific policies that are designed to protect water supplies for agricultural use are needed.

Application of water footprint combined with a unified virtual crop pattern to evaluate crop water productivity in grain production in China

Water shortages are detrimental to China's grain production while food production consumes a great deal of water causing water crises and ecological impacts. Increasing crop water productivity (CWP) is critical, so China is devoting significant resources to develop water-saving agricultural systems based on crop planning and agricultural water conservation planning. A comprehensive CWP index is necessary for such planning. Existing indices such as water use efficiency (WUE) and irrigation efficiency (IE) have limitations and are not suitable for the comprehensive evaluation of CWP. The water footprint (WF) index, calculated using effective precipitation and local water use, has advantages for CWP evaluation. Due to regional differences in crop patterns making the CWP difficult to compare directly across different regions, a unified virtual crop pattern is needed to calculate the WF.This project calculated and compared the WF of each grain crop and the integrated WFs of grain products with actual and virtual crop patterns in different regions of China for 2010. The results showed that there were significant differences for the WF among different crops in the same area or among different areas for the same crop. Rice had the highest WF at 1.39m3/kg, while corn had the lowest at 0.91m3/kg among the main grain crops. The WF of grain products was 1.25m3/kg in China. Crop patterns had an important impact on WF of grain products because significant differences in WF were found between actual and virtual crop patterns in each region. The CWP level can be determined based on the WF of a virtual crop pattern, thereby helping optimize spatial distribution of crops and develop agricultural water savings to increase CWP.

Response of evapotranspiration and yield to planting density of solar greenhouse grown tomato in northwest China

Selecting proper planting density can optimize light interception and increase crop water productivity. This research investigated the planting density effect on the evapotranspiration (ETc) and yield of greenhouse grown tomato in northwest China during December 2010 to June 2011 (first season), and September 2011 to January 2012 (second season). Five planting density treatments of 3.1, 3.7, 4.4, 5.0 and 5.6plantsm−2 were used and each treatment was replicated three times. The fifteen plots were randomized complete block design. The irrigation scheduling adopted was the same for all treatments and referred to a soil water depletion of 25±2% below field capacity as observed for the 4.4plantsm−2 treatment. Water was applied beneath the plastic mulch covering both the bed and the furrow. The FAO 56 Penman–Monteith equation with a fixed aerodynamic resistance of 295sm−1 was used to estimate the reference evapotranspiration (ET0) in the greenhouse. The ETc was calculated by the water balance method according to the change in soil water content over a period of time. The crop coefficients (Kc) at crop development stage in both growth seasons were calculated from ETc/ET0 and estimated by the equations proposed by Allen and Pereira (2009) that consider a plant density coefficient. Tomato yield and fruit number were also measured to assess the planting density effect on water productivity. Results showed that the seasonal total ETc of the greenhouse grown tomato increased, while the seasonal total ETc per plant decreased, linearly as planting density increased in both growth seasons. The calculated middle season Kc values from ETc/ET0 ranged from 0.77 to 0.83 in the first season and from 0.94 to 0.97 in the second season for different planting densities, which were lower than the Kc values estimated by Allen and Pereira's approach. Fruit number per plant, average single fruit weight and yield per plant decreased, but total yield increased, as planting density increased. From economical perspective, the recommended planting densities of tomato grown in northwest China's greenhouses are 3.7–4.4plantsm−2.

Assessing crop yield and crop water productivity and optimizing irrigation scheduling of winter wheat and summer maize in the Haihe plain using SWAT model

AbstractHaihe plain is an important food production area in China, facing an increasing water shortage. The water used for agriculture accounts for about 70% of total water resources. Thus, it is critical to optimize the irrigation scheduling for saving water and increasing crop water productivity (CWP). This study first simulated crop yield and CWP for winter wheat and summer maize in historical scenario during 1961–2005 for Haihe plain using previously well‐established Soil and Water Assessment Tool model. Then, scenarios under historical irrigation (scenario 1) and sufficient irrigation (scenario 2) were, respectively, simulated both with sufficient fertilizer. The crop yield in scenario 2 was considered as the potential crop yield. The optimal irrigation scheduling with sufficient fertilizer (scenario 3) was explored by iteratively adjusting irrigation scheduling based on the scenario 1 and previous studies related to water stress on crop growth. Results showed that net irrigation amount was, respectively, reduced 23.1% and 18.8% in scenario 3 for winter wheat and summer maize when compared with scenario 1. The CWP was 12.1% and 8.2% higher with very slight change of crop yield. Using optimal irrigation scheduling could save 8.8 × 108 m3 irrigation water and reduce about 16.3% groundwater over‐exploitation in winter wheat growth period. The corresponding yield was 18.5% and 12.9% less than potential yield for winter wheat and summer maize but using less irrigation water. Therefore, it could be considered that the optimal irrigation was reasonable, which provided beneficial suggestions for increasing efficiency of agricultural water use with sustainable crop yield in Haihe plain. Copyright © 2013 John Wiley & Sons, Ltd.

Crop Water Productivity of Irrigated Teff in a Water Stressed Region

In water stressed regions such as the Central Rift Valley of Ethiopia, increasing Crop Water Productivity (CWP) is imperative for sustainable food and water security. This paper presents CWP of Teff (Eragrostic Tef), a staple food in Ethiopia and an important export crop. Field experiments were conducted under irrigated agriculture during the dry seasons in the periods: 1) November 2010 to March 2011; and 2) December 2011 to April, 2012 at Melkassa Agricultural Research Centre in Ethiopia. Teff crop was irrigated at sixteen different water application depths ranging from 100 to 25 % of the optimum Crop Water Evapotranspiration (ETc.) during the four growing stages, the initial, development, mid season and late season. The effect of seeding rates of 25 kg/ha and 10 kg/ha on lodging and yield of the crop was also determined. The main results were: 1) At 25 % deficit irrigation applied for the whole growth period, Teff CWP was the highest at 1.16 and 1.08 kg/m3 respectively for the seeding rates of 25 kg/ha and 10 kg/ha; 2) the CWP slightly decreased to 1.12 and 1.07 kg/m3 when the 25 % deficit was applied during the late season stage; 3) the crop yield response factor (Ky) of 1.09 and 1.19 was obtained for seeding rates of 25 kg/ha and 10 kg/ha respectively; the equivalent biomass response factor (Ky) was less at 0.88 and 0.96 respectively.

Estimation of Water Consumption of Lowland Rice in Tropical Area based on Heterogeneous Cropping Calendar Using Remote Sensing Technology

Abstract Irrigated agricultural sector meets challenge in using water efficiently and effectively while improving food acquisition. One of the strategies to increase food production dealing with water scarcity is by increasing crop water productivity. Spatial data of crop water productivity parameters on large area is needed to support better water resources management. Remote sensing provides viable means to meet requirement of improved regional-scale data set of crop water productivity, such as crop water consumption (evapotranspiration) and crop yield. A methodology is developed to quantify spatial variation of seasonal evapotranspiration (ET) of lowland rice in paddy field with heterogeneous cropping calendar using satellite data. The methodology is developed by synthesizing SEBAL (Surface Energy Balance Algorithm for Land) method and lowland rice phenology detection method. Study area is located in the northern part of West Java Province, known as Pantura Jawa Barat region. The developed method is able to describe spatial variability of lowland rice evapotranspiration in Pantura Jawa Barat region for the growing period of dry season year 2004. The average seasonal actual evapotranspiration of rice is found to be 274.5 mm/season with standard deviation ± 44.7 mm/season.