Increasing Crop Water Productivity Research Articles

Optimizing yield and water productivity in summer mung bean (Vigna radiata L.) through crop residue management and irrigation strategies

A multi-season research trial entitled ‘crop residue management effects on yield and water productivity of summer mung bean (Vigna radiata L.) under different irrigation regimes in Indian Punjab’ was conducted at Punjab Agricultural University (PAU), Regional Research Station (RRS), Bathinda, during rabi 2020 and 2021. The field experiment was conducted in a split-plot layout with nine treatment combinations and replicated thrice. The treatments consisted of T1 (no wheat residue along with tillage), T2 (leftover wheat residue with zero tillage), and T3 (incorporated wheat residue along with tillage) in main plots and irrigation regimes viz., I1 (vegetative growth and flowering stage), I2 (vegetative growth, flowering, and pod filling stage) and I3 (vegetative growth, flowering, pod formation and pod filling stage) in sub-plots, respectively. The growth and yield attributing characters were significantly higher under T3 than T1 but statistically at par with T2 during both years. An increase of 24.1% and 19.0% in grain yield was found in residue incorporation (T3) and residue retention (T2) over residue removal (T1), respectively. Maximum crop and irrigation water productivity was observed under T3 due to reduced water use and increased yield. Among the irrigation regimes, the I3 recorded significantly higher grain yield (0.70 and 0.79 t ha− 1) than I1. It was at par with I2 during both years due to higher irrigation frequency at the pod formation and pod filling stage. Crop water productivity (CWP) was higher under I3, whereas irrigation water productivity (IWP) was higher under I1 during both years. Additional irrigation at the pod-filling stage increased the grain yield by 36.5%, and two additional irrigations at the pod-formation and pod-filling stage further increased yield by 46.2% compared to only two irrigations at the vegetative and flowering stages. The treatment combinations of T2I2 and T3I2 outperformed T1I3 in terms of growth and yield attributing characters viz. plant height, dry matter accumulation (DMA), leaf area index (LAI), pods plant− 1, seeds pod− 1, and 1000-seed weight, which resulted in higher grain yield in these treatment combinations over T1I3. Applying crop residue can help minimize water use and increase crop water productivity. So, retaining crop residue in summer mung bean resulted in saving irrigation water due to lesser evapotranspiration from the soil surface.

Evolution of global water footprints of crop production in 1990–2019

Abstract Crop production has the largest water footprint (WF) of all economic sectors and ranks as a leading cause of water scarcity. Despite this, our understanding of historical changes in global WFs of crops remains limited. In this study, we analyse the recently published dataset on green and blue WFs of 175 individual crops in 1990–2019. We explore the main changes in unit WFs (expressed in m3t−1 yr−1) and WFs of production (m3 yr−1) and connect the observed changes to various physical and socio-economic drivers. We find that nearly 80% of crops reduced global average unit WFs (required less water per tonne) as crop yields improved and cultivation centred around more productive areas. However, the total WF of crop production increased by 30% as these productivity gains were insufficient to compensate for cropland expansion of mostly water-intensive crops. Close to 90% of the increase occurred between 2000–2019 likely driven by accelerated economic growth, globalisation, changing diets, and production of first-generation biofuels. Among crops, we observe the largest increases for oil palm fruit, soya beans, and maize as they became the main providers of crop-based nutrients, animal feed, and biofuels for the modern economy. Among regions, most of the increase occurred across the tropics, mainly in Indonesia, Brazil, and Nigeria. However, India, China, and the USA had the largest WFs of production over the study period. Humanity consumed 6.8 trillion m3 of water (87.1% green) to produce crops in 2019. This number is likely to increase in the future which may exacerbate already existing environmental and socio-economic issues. Thus, it is important to transition to more water-sustainable agrifood systems. Much potential still exists in increasing crop water productivity, shifting production to less water-scarce geographies, and rethinking our dietary and industrial consumption patterns.

Combined effect of silicon and nitrogen doses applied to planting furrows on sugar, biomass and energy water productivity of sugarcane (Saccharum spp.)

Brazil has the largest cultivated area for sugarcane in the world, with a predominance of rain-fed production systems (64%) and marginal areas that are subject to frequent water deficits. The remaining 36% under cultivation is equipped with irrigation systems; however, a significant portion of these irrigation systems (76%) is dedicated to crop maintenance. Their primary purpose is to provide water for initial plant maintenance during planting and regrowth of ratoons, which helps to alleviate drought stress caused by water scarcity during dry periods. The remaining 24% of the irrigated sugarcane production areas use deficit and full irrigation strategies to partially (50%) and fully (100%) meet the plants’ water demands, respectively. Therefore, a large part of the cultivated area for sugarcane in Brazil is subject to a water deficit at one or more stages of the crop's development cycle, which can retard plant growth, nutrient use and productivity. One potential strategy for mitigating these harmful effects is the application of silicon (Si) in the furrow at planting, which can also increase crop water productivity (WPc). The objective of this research was to determine the effects of different applications of Si and nitrogen (N) on WPc, in terms of sugar (SWPc), biomass (BWPc) and energy (ENWPc) for sugarcane crop. The research was conducted at the University of São Paulo (USP/ESALQ), Piracicaba, São Paulo State, Brazil. The experimental design involved randomized blocks, with four blocks and 12 treatments. The treatments consisted of three applications of Si, 175, 350 and 525 kg·ha−1 and four N treatments of 15, 30, 60 and 90 kg·ha−1. Biometric responses, effects on juice quality, and indices related to yield and WPc were determined. The water consumption and agricultural yield (AY) of sugarcane were clearly influenced by the treatments. The lowest water consumption was obtained with the 15Nx350Si treatment, 561 mm per year. The treatment with the highest AY value was 60Nx350Si (162.3 Mg·ha−1). The SWPc, BWPc and ENWPc of the sugarcane crop were affected by the different application rates of N and Si. In general, the highest average WPc values were obtained with the 15Nx350Si treatment (SWPc=2.6 kg·m−3, BWPc=10 kg·m−3 and ENWPc=224.5 MJ·m−3). The different N and Si treatments did not significantly affect biometric variables (except for fresh biomass and leaf area) or juice quality; therefore, Si application did not compromise the quality of the end-product.

Climate-smart technologies for reducing water footprints in different cropland ecosystems: a meso analysis

Water footprints (WFs) in crop production are an ecological measurement of water utilization that represents the cumulative groundwater quantum consumed within a region (district/state or country) to produce the crops. WFs in crop production have great significance for ecosystem’s sustainability, as high WFs are posing a serious challenge for the scientists and presents researchable issues for reducing WFs for increased crop water productivity. Crop need based approaches and improved climate smart technologies (CSTs) instead of conventional approaches help in reducing the irrigation water use without compromising crop yields. In view of global warming, need to reduce the water intake in agricultural production has been thought as an urgently sustainable issue. Amongst various crops of South Asia, rice–wheat cropping system extensively cultivated on ~ 12.5 million ha (Mha), has large WFs. A large scale field experimentation suggested several permissible techniques having overwhelming significance for reducing WFs in crop production. Amongst the several CSTs, laser levelers for precision leveling, cultivars with short duration rice varieties, delayed transplanting of rice seedlings, soil matric potential (or tensiometer) based irrigation scheduling, direct drilling of rice seeds, crop establishment on permanent beds, mechanical rice seedling transplanting, and crop diversification through oilseed/pulses has considerable significance in water saving and decreased WFs. Nonetheless, all technologies are not universally efficient in reducing WFs, and depend up on several factors of which soil texture and climatic conditions are the major determinants. For feeding the burgeoning population and to sustain and/or increased food production, technological focus should be on widespread adoption of technologies which aims at reduced WFs either by decreasing water loss from the leaf and/or soil. The present review deals with WFs in crop production, and the technologies to enhance irrigation water productivity and ecosystems’ sustainability of predominant cropping system of South Asia, particularly in water-harassed regions.

Characterizing Evaporative Losses From Sprinkler Irrigation Using Large Weighing Lysimeters

Highlights Losses for MESA and LESA were comparable on the day of irrigation and oftentimes greater for the subsequent day. Losses were greater due to incomplete canopy conditions for both MESA and LESA on both days. Evaporative losses from irrigation extended to at least the subsequent day following irrigation in most cases. Losses over two days accounted for as much as 39.5% and 28.0% of irrigation depth for MESA and LESA, respectively. Abstract. Effective irrigation systems that increase crop water productivity by minimizing evaporative losses are paramount for extending the longevity of finite groundwater resources in the semi-arid U.S. Southern High Plains (SHP). Although subsurface drip irrigation (SDI) acreage has increased in recent years, center-pivot sprinkler systems still account for greater than 85% of the irrigated area in the SHP. Modern sprinkler configurations are typically classified according to application height as either mid-elevation spray application (MESA) or low-elevation spray application (LESA). While application drift and evaporative losses are easily measured under fallow conditions, quantifying evaporative losses under cropped conditions is difficult. Lysimeter-derived daily evapotranspiration (ET) values for SDI-irrigated and sprinkler-irrigated fields planted to corn in 2016 (MESA) and 2018 (LESA) near Bushland, TX, were compared for days when sprinkler irrigation events occurred and for subsequent days, when possible. Differences (extra ET) were attributed to evaporative losses associated with MESA and LESA irrigation. Average daily extra ET values for both sprinkler irrigation methods were similar on the day of irrigation, although MESA was slightly larger than LESA at 1.4 and 1.2 mm, respectively. The average daily extra ET values for incomplete canopy conditions were 2.2 mm for MESA and 1.9 mm for LESA, while values were identical for both methods at 0.6 mm for full canopy conditions. Average daily extra ET values were also expressed as a percentage of daily standardized grass reference ET (ETos) values. Average values for MESA and LESA were 20.1% and 13.5%, respectively, for the season, with similar findings of 29.3% and 19.4% for incomplete canopy conditions. Average extra ET/ETos values for incomplete canopy conditions were similar at 7.5% and 7.7% for MESA and LESA, respectively. Evaporative irrigation losses, calculated as the percentage of extra ET to irrigation depth, were slightly larger overall for the day of irrigation for MESA (5.4%) than LESA (5.2%). Losses of 7.9% and 7.0% were observed for incomplete canopy conditions for MESA and LESA, respectively. Average losses for LESA (3.5%) under full canopy conditions were greater than those for MESA (1.9%). A comparison of extra ET values for days following irrigation revealed that evaporative losses from irrigation events extended beyond the day of irrigation. MESA extra ET values for the day following irrigations increased by 57.1% (2.2 mm) overall, 13.6% (2.5 mm) for incomplete canopy conditions, and 150.0% (1.5 mm) for full canopy conditions. The same was true for LESA, with increases of 125.0% (2.7 mm) overall, 78.9% (3.4 mm) for incomplete, and 216.7% (1.9 mm) for full canopy conditions. Summing of extra ET values for the day of irrigation and the subsequent day yielded average values more than double those for the day of irrigation only, at 3.9 and 4.3 mm for MESA and LESA, respectively. Similarly, values for extra ET as a percentage of irrigation depth were also more than double those for the day of irrigation only, with the greatest loss values of 39.5% for MESA and 28.0% for LESA. These findings suggest that although LESA appears to mitigate evaporative losses marginally more in corn than MESA on the day of irrigation, considerably more evaporative losses occurred for both methods during the subsequent day, with slightly increased losses for LESA, resulting in little difference between overall losses over the two days. This may in part be explained by the temporary cooling effect of the irrigation inside the canopy on the day of irrigation, which is diminished by the second day. A greater discrepancy between evaporative losses for MESA and LESA is likely to be observed for crops having shorter stature or lower leaf density, such as cotton, although more study is needed to corroborate this claim. Knowledge of these findings provides useful information for both producers and water managers when considering irrigation management and water planning strategies. Keywords: Evaporation, Evapotranspiration, LESA, MESA, Semi-arid, Sprinkler Irrigation, Subsurface Drip Irrigation, Transpiration, Weighing Lysimeters.

Delayed irrigation at the jointing stage increased the post-flowering dry matter accumulation and water productivity of winter wheat under wide-precision planting pattern.

The North China Plain (NCP) faces a severe water shortage, and the amount of rainfall cannot guarantee the growth and development of winter wheat. Therefore, it is important to explore a suitable irrigation and planting pattern to solve the problem of water shortage in this region. A 4-year experiment was carried out in the NCP during 2015-2019. The main plots included two planting patterns: a wide-precision planting pattern (W) and a conventional planting pattern. Two irrigation regimes were established for each planting pattern: 60-mm irrigation at the jointing stage (I1) and 60-mm irrigation delayed 10 days at the jointing stage (I2). The soil water consumption, dry matter translocation, grain yield and crop water productivity were investigated. The results showed that WI2 treatment obtained the highest grain yield and crop water productivity. The wide-precision planting pattern could significantly decrease soil water consumption; however, delayed irrigation effectively reduced soil water consumption only in normal rainfall years. The coupling of delayed irrigation at the jointing stage and a wide-precision planting pattern significantly enhanced dry matter accumulation after flowering and the contribution of dry matter accumulation after flowering to grain yield during the growing seasons. WI2 could decrease the evapotranspiration and improve the grain yield, thus increasing crop water productivity. The combination of a wide-precision planting pattern and delayed irrigation at the jointing stage was the appropriate agronomic practice for efficient grain yield and crop water productivity in the North China Plain. © 2022 Society of Chemical Industry.

Optimizing urea deep placement to rainfall can maximize crop water-nitrogen productivity and decrease nitrate leaching in winter wheat

The deep placement of urea fertilizer is considered an effective strategy for crop growth and yield formation. How crop root morphology and resource utilization respond to altered rainfall amount and deep urea fertilizer placement is still not fully understood. Thus, we conducted a two-year field experiment in the semi-humid region to assess the effects of different urea fertilizer placement depths of 5 cm (D5, conventional surface fertilization), 15 cm (D15), 25 cm (D25), and 35 cm (D35) under three rainfall conditions (dry year = 125 mm, P125; normal year = 200 mm, P200; wet year = 275 mm, P275) on root distribution, resource utilization and yield of wheat. Deep urea placement significantly increased root length density and root weight density in the 20–60 cm soil layer, which caused a significant increase in wheat nitrogen (N) uptake. Compared with D5, deep urea placement significantly increased the crop N uptake (10.4–27.6 %), grain N content (1.2–18.7 %), N recovery efficiency (NRE, 0.9–16.7 %) and N partial productivity (PFPN, 1.1–20.0 %) in dry and normal years, and D15 promoted those by 0.9 %, 1.3 %, 3.7 % and 1.1 % over D5 under wet year. Additionally, compared with D5, deep urea placement increased crop water productivity (WP) and yield by 9.6–23.9 % and 3.2–20.0 % under dry and normal years, and D15 increased those by 1.1 % and 0.5 % in wet year. The accumulated nitrate contents in the 0–100 cm soil layer was 4.7–14.5 % higher under deep urea placement than D5. Placement of urea at depths of 28.0–30.0 cm, 20.7–21.6 cm and 12.3–13.1 cm in the dry, normal and wet years maximized the wheat yield, grain N content and WP. Moderate deep urea placement according to variable precipitation conditions can be an effective fertilizer management strategy for sustainable wheat development.

Effects of mulching on water saving, yield increase and emission reduction for maize in China

Mulching, an agricultural management measure widely used in arid and semi-arid regions of China, can effectively improve the hydrothermal environment of farmland and increase crop yield and crop water productivity (WPc). However, previous studies on the effects of mulching on water saving, yield increase and emission reduction of maize have provided inconsistent results. Therefore, a meta-analysis was used in this study to (1) evaluate the effect of mulching types [plastic film (PM), straw (SM) and degradable film (DM)] on maize yield, evapotranspiration, WPc and greenhouse gas emissions; and (2) determine the effects of mulching measures on water saving, yield increase and emission reduction in maize farmland under different climatic conditions. Compared with the no-mulching control, mulching significantly raised maize yield, WPc and carbon dioxide (CO2) and nitrous oxide (N2O) emissions. The PM, SM and DM increased maize yield by 27.31 %, 6.98 % and 16.55 % compared with no-mulching, respectively, and correspondingly WPc by 34.08 %, 11.48 % and 24.20 %. The PM and SM significantly increased CO2 emissions by 39.91 % and 16.43 %, respectively, and N2O emissions by 51.1 % and 30.12 %, but had no significant effect on methane absorption. For maize planting, in areas with altitudes < 500 and > 1000 m, average annual rainfall < 1000 mm, average annual air temperature of 5–15 °C and average annual evaporation < 1500 mm, a combination of PM and ridge–furrow planting can achieve the best effect of increasing production and saving water. In areas with an altitude of 1000–1500 m and average annual evaporation of 1500–2000 mm, the DM had the greatest effect of improving yield (by 16.17 %) and saving water, with a decrease in evapotranspiration of 8.82 % and an increase in WPc of 24.71 %. The local level of mechanization and labor costs should be considered when choosing a maize mulching pattern.

Deficit irrigation impacts on greenhouse gas emissions under drip-fertigated maize in the Great Plains of Colorado.

Precise water and fertilizer application can increase crop water productivity and reduce agricultural contributions to greenhouse gas (GHG) emissions. Regulated deficit irrigation (DI) and drip fertigation control the amount, location, and timing of water and nutrient application. Yet, few studies have measured GHG emissions under these practices, especially for maize (Zea mays L.). The objective was to quantify N2 O and CO2 emission from DI and full irrigation (FI) within a drip-fertigated maize system in northeastern Colorado. During two growing seasons of measurement, treatments consisted of mild, moderate, and extreme DI and FI. Deficit irrigation was managed based on growth stage so that full evapotranspiration (ET) was met during the yield-sensitive reproductive stage, but less than full crop ET was applied during the late vegetative and maturation growth stages. In the first year, mild DI (90% ET) reduced N2 O emissions by 50% compared with FI. In the second year, compared with FI, moderate DI (69-80% ET) reduced N2 O emissions by 15%, and extreme DI (54-68% ET) reduced N2 O emissions by 40%. Only extreme DI in the second year significantly reduced CO2 emissions (by 30%) compared with FI. Mild DI reduced yield-scaled emissions in the first year, but moderate and extreme DI had similar yield-scaled emissions as FI in the second year. The surface drip fertigation resulted in total GHG emissions that were one-tenth of literature-based measurements from sprinkler-irrigated maize systems. This study illustrates the potential of DI and drip fertigation to reduce N2 O and CO2 emissions in irrigated cropping systems.

Transparent plastic film combined with deficit irrigation improves hydrothermal status of the soil-crop system and spring maize growth in arid areas

Plastic film mulching and irrigation amount greatly affect soil hydrothermal status and spring maize (Zea mays L.) productivity in arid areas. Yet the coupled effects of film mulching with different optical properties and deficit irrigation on water and temperature variation within the soil-crop system and on plant growth in arid areas have not been well-investigated. A two-year field experiment was conducted with five treatments: 1) full irrigation without mulching (FN), 2) full irrigation with transparent plastic film mulching (FT), 3) full irrigation with black plastic film mulching (FB), 4) deficit irrigation with transparent plastic film mulching (DT), and 5) deficit irrigation without mulching (DN). The results showed that plastic film mulching significantly increased soil water in the 80–120 cm soil layer and canopy air humidity. The alternating wet-dry behavior of soil water caused by plastic film mulching was an effective water utilization strategy that increased crop water productivity. DT stimulated the alternating wet-dry behavior of soil water in the 0–80 cm layer more than the FN. This alternating behavior was characterized by relatively wet soil at the 12-leaf growth stage (V12), relatively dry soil from V12 to the grain-filling growth stage (R3), and relatively wet soil again after R3. Alternating wet-dry behavior changed from wet to dry at V12 in 2019 and was earlier than V12 in 2020. Plastic film mulching significantly increased soil temperature at the six-leaf growth stage (V6) and decreased canopy air temperature during the whole maize growing seasons. The higher net photosynthesis rate was observed at the canopy air relative humidity of 78.6%. Net photosynthesis rate decreased with increasing canopy air temperature. FT, FB, DT, and FN significantly increased grain yields over DN by 39.7–45.8%, 25.5–41.8%, 18.2–33.4%, and 9.0–17.0%, respectively, and increased net income over DN by 894–1127, 436–979, 343–844, and 166–429 USD ha–1, respectively. DT decreased net income and output/input ratio by 28.1% and 10.9% in 2019, respectively, compared with FT. However, these values were 12.3% and 4.0% in the relatively wet growing season in 2020. Deficit irrigation combined with transparent plastic film mulching can ensure an acceptable maize grain yield and net income in arid areas with limited water resources, especially in growing seasons with greater rainfall.

Effects of regulated deficit irrigation on crop water productivity, yield components, and yield response factor of common bean (Phaseolus vulgaris L)

Due to declining water resources allocated to agriculture and rapid population growth, it is important to use water efficiently and increase crop water productivity (CWP). Deficit irrigation is considered an important strategy to achieve this goal. For this purpose, field experiments were conducted at the research farm of the Agriculture Faculty on Kabul University campus for two continuous years (2018-2019). The experiment consisted of four treatments, including full irrigation (ET100), 80% (ET80), 60% (ET60), and 40% (ET40) arranged in a randomized complete block design with three replications. Compared to ET100 and ET80, the ET60 and ET40 treatments significantly (P&lt;0.05) reduced the duration of flowering and pod formation. The bean crop also showed best performance in plant height, number of leaves per plant, leaf area, leaf area index, number of pods per plant, number of seeds per pod, length of pod, 100-seed weight, and total grain yield in the ET100 and ET80 treatments. Moreover, significantly greater values of crop water productivity (CWP) and lower value of Ky were observed in ET80 compared to ET100, ET60 and ET40. Overall, the experiment results showed that regulated deficit irrigation can effectively increase water productivity. Supplying only 80% instead of full water requirement can result in a higher common bean CWP. This is of particular importance in water-scarce areas, where the water saved based on this practice can be used to irrigate additional acreage.

Cover crop water use and corn silage production in -semi-arid irrigated conditions

Cover crops can increase crop water productivity (CWP) and succeeding crop yield. However, cover crops adoption in the Southern High Plains of USA is slow due to limited water available for crop production. This study evaluated the effects of winter cover crops on soil water dynamics, corn silage yield and nutritive values, and corn silage CWP in a semi-arid irrigated condition. Three winter cover crop mixtures: grasses + brassicas + legumes (GBL), grasses + brassicas (GB), grasses + legumes (GL), and control or no cover crop (NCC) were evaluated for soil water storage, cover crop biomass, corn silage yield, nutritive values, and crop evapotranspiration (ET), and the cover crop-corn silage system water productivity (SWP) under a no-till irrigated corn silage production system. All cover crop treatments reduced soil water storage before their termination in both years. However, water storage was higher for all cover crop treatments than for NCC during corn growth. Average CWP for corn was improved by 14–29% with cover crop mixtures over the NCC. Corn silage yield among cover crop treatments was 9–26% higher than NCC. Nutritive value components of cover crops such as non-fat carbohydrates, relative forage quality, and Ca and Mg were higher in the GBL and GL mixtures than the GB in one of the two years. This study demonstrated increased corn silage yield and water productivity with cover cropping. Cover crops mixtures with legumes could offer a high-quality alternative forage for crop-cattle integrated systems, including dairy producers in the Southern High Plains region.

Increasing pit‐planting density of rice varieties with different panicle types to improves sink characteristics and rice yield under alternate wetting and drying irrigation

AbstractThe Chinese government regards ensuring food security and developing water‐saving agriculture as an important national strategy and that carrying out relevant research has important practical significance and production application value. A two‐year field experiment was conducted to explore the compensation potential in rice yield by using rice varieties with different panicle size under two water management regimes (conventional water management or CWM and alternate wetting and drying or AWD). The results showed that the large panicle rice variety resulted in greater yield, crop water productivity, spikelet density, dry matter accumulation and translocation, and photosynthesis. Compared with the CWM, the AWD had little effect on rice yield. However, with an appropriate planting density, the AWD achieved a greater grain yield compared with the CWM. Moreover, the AWD increased crop water productivity and the grain‐filling efficiency. The loss of spikelets under the AWD could be compensated by increasing the planting density. Although AWD reduced tillering number, it increased the photosynthetic rate, dry matter accumulation and its translocation to grain, and leaf area index. In addition, the adverse effects on rice growth and the yield caused by the AWD could be alleviated by increasing planting density of rice. Therefore, an appropriate planting density can be used to save water and maintain high grain yield of rice under alternate wetting and drying.

Simulating the effects of irrigation and tillage on soil water, evapotranspiration, and yield of winter wheat with RZWQM2

Agricultural water shortages threaten food security worldwide, particularly in the North China Plain (NCP) which is an important grain production base in China. To solve this problem, we studied the effects of two tillage methods (no tillage: NT and plow tillage to 15 cm: PT) combined with two different irrigation timing (I1, 60 mm at the jointing stage and I2, 60 mm at 10 days after the jointing stage) on the grain yield of winter wheat and crop water productivity (CWP). The experimental results were used to calibrate the RZWQM2 model to improve its application in the NCP. The simulation results of the model could be used to compensate for the shortcomings of field experiments. The RZWQM2 model was calibrated and validated using the winter wheat growth data from 2015 to 2019. The normalized root mean square error (calibration and validation) between simulated and measured soil water storage (SWS), evapotranspiration (ET), leaf area index (LAI), biomass, and grain yield was 8.43 %–11.99 %, 4.39 %–8.67 %, 13.71 %–19.87 %, 16.37 %–19.36 %, and 13.83 %–17.71 %, respectively. NT improved the measured soil moisture status but decreased measured yield. However, I2 compensated for the negative effect of NT and resulted in a higher measured CWP than that after I1. The modified RZWQM2 model was used to calculate the actual transpiration and actual evaporation (AE) to expand the experimental results and reveal the effect of different treatments on actual evapotranspiration (AET). NT reduced the simulated AE during the entire growth period, reducing AET and increasing CWP. However, compared with the simulation effect of SWS and ET, the simulation effect of LAI, biomass, and grain yield was worse, and it was evident that improvements to the plant growth model are required. This study demonstrated that NT combined with delayed irrigation (10 days after the jointing stage) can improve soil moisture status and increase CWP in the NCP.

Impact of soil water regimes and partial root-zone drying in field-grown papaya in semi-arid conditions

This study aimed to evaluate in the papaya Tainung genotype, the effects of partial root-zone drying (PRD) technique on soil water regimes by using different frequencies of shifting irrigation-side of plant row and the effects of PRD technique on (1) crop agronomic performance, (2) titratable fruit acidity (TA), (3) total soluble solids (TSS), and TSS/TA ratio. Also, we analyze the spatial dynamic of papaya condition using normalized difference vegetation index (NDVI) from different satellite images. The study was conducted in the semi-arid region of Bahia (BA) and Minas Gerais (MG), Brazil. The combination of 100% (Full irrigation—FU), 50%, and 35% in the irrigation depth (WID) and frequencies of shifting plant-row side irrigation of 0 (Fixed Irrigation—FX), 7, 14, and 21 days were applied. Nine treatments were studied in BA and five in MG. The water available in the soil was reduced to 44% for frequencies of shifting plant-row side irrigation of 7 days, 50% for 14 days, and 85% for 21 days, compared to the soil water availability at field capacity. Partial water deficit in the soil through the PRD technique did not significantly reduce the total root length, effective root depth, and root effective horizontal distance of the papaya Tainung genotype. However, PRD treatments showed leaf abscission, which resulted in reduced leaf area and NDVI values, especially in the MG experiment. Papaya yield and fruit quality were not affected. However, except for PRD 21 35%, irrigation water depth reduced to 50 and 35% under PRD increased crop water productivity (CWP) in papaya plants. Thus, the PRD technique may save 35% of WID using the alternation of lateral shift irrigation of crop row every 7 days under water scarcity in semi-arid regions. The NDVI index was important to compare the papaya canopy vigor between the experimental areas studied. We also confirmed the potential of NDVI to monitor the vigor of papaya canopy, since we could notice the sensibility of NDVI to identify water stress in papaya in higher vapor pressure deficit (VPD) conditions occurred in October 2016 and January 2017 in Bom Jesus da Lapa-BA. Therefore, the PRD strategy can be a useful tool to save water in papaya cultivation under semi-arid conditions.

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

<List><ListItem><ItemContent> • The linkage between crop water productivity and soil properties were summarized </ItemContent></ListItem><ListItem><ItemContent> • Knowledge of soil microbial effects on crop water productivity is still limited </ItemContent></ListItem><ListItem><ItemContent> • Knowledge of interactions of soil factors on crop water productivity is still limited </ItemContent></ListItem></List> 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.

Water productivity and its allometric mechanism in mulching cultivated maize (Zea mays L.) in semiarid Kenya

Allometry is extensively used to describe the scaling relationship between individual size and metabolite allocation. Micro-field rain-harvesting system can improve soil water availability and thus alter the allocation of individual biomass among organs. Yet the eco-physiological mechanism based on allometric scaling theory has been little investigated under various mulching conditions. A field experiment was conducted using maize variety Yuyuan7879 in Juja, Kenya for two growing seasons (cross-year) from 2015 to 2016, and from 2016 to 2017 respectively. Four treatments were designed as ridge-furrow mulching (RFM) with black plastic mulching (RFMB), transparent plastic mulching (RFMT), grass straw mulching (RFMG) and conventional flat planting (CK). We found that RFMB, RFMT and RFMG significantly increased grain yield by 106%, 109% and 32% in 2015, and 101%, 96% and 30% in 2016 respectively, in comparison with CK. Mulching treatments improved soil temperature and moisture and significantly increased crop water productivity (CWP). Mulching treatments drastically changed the allometric relationship between metabolic rate (leaf biomass) and individual size (lgy = αlgx + lgβ), and optimized the size-dependent reproductive allocation. In the relationship between leaf biomass (y-axis) vs aboveground biomass (x-axis), mulching treatments significantly declined the value of α (α < 1; P < 0.01), suggesting that less photosynthetic product was allocated in leaves in mulching treatments than in CK. As for the allometric relationship between grain yield and aboveground biomass, the α was generally significantly more than 1 in RFMB and RFMT, and significantly less than 1 in RFMG and CK, demonstrating that more photosynthates were allocated to reproductive growth under plastic mulching. Also, the variation of allometric relationship between reproductive and vegetative biomass provided further evidence that plastic mulching facilitated substance transportation from vegetative to reproductive organs. In conclusion, plastic mulching significantly improved soil hydrothermal condition, increased individual reproductive allocation and ultimately improved grain yield and CWP at population level.

Effect of using pruning waste as an organic mulching on a drip-irrigated vineyard evapotranspiration under a semi-arid climate

ABSTRACT In a drip-irrigated vineyard soil evaporation (E) can reach up to 30-40% of the seasonal grapevine crop evapotranspiration (ETc). Vineyard soil management can be used as a technique to reduce soil E for improving crop water use efficiency. The aim of this experiment was to analyze the effect of using pruning waste as an organic mulching on vineyard ETc. During three experimental seasons, several cycles of grapevines water use determinations were conducted using a large weighing lysimeter located in Albacete (southeast Spain) under drip irrigation. Measurements were carried out under different soil management practices: i) keeping the bare soil within the lysimeter during the first 2-3 days (bare soil), ii) covering the lysimeter soil surface with pruning waste as an organic mulching (about 5 cm thick) for the next 2-3 days (organic mulch), and iii) covering the lysimeter with a waterproof canvas (plastic mulch), similar in colour to the soil, for the last 2-3 days of each measurement cycle. In 2017, the measurements period was initiated when midday stem water potential (Ψstem) values reached -1.3 MPa, in order to study the effect of the different soil management on grapevine ETc when vines in the lysimeter were suffering from severe water stress. During the 3-year study, plant determinations (i.e., canopy cover and the phenological stage) showed that vines were at the same stage of development during each period of measurements. Under equal evaporative demand and fractional canopy cover, results showed a reduction in the vineyard ETc between 16-18% with the organic mulching, and up to 24-30% with the plastic mulching. Even though plastic mulches significantly reduced water evaporation from soil surface, this reduction could have resulted in an increase in crop transpiration (T). However, results in this experiment show that both organic and inorganic mulching did not increase vine T compared to no mulching conditions, based on vine T values estimated during the three experimental periods of 2015. Therefore, using pruning waste as an organic mulch could be an environmental friendly alternative to reduce soil evaporation and increase crop water productivity in large areas where vineyards are drip-irrigated.

Alternate furrow irrigation can maintain grain yield and nutrient content, and increase crop water productivity in dry season maize in sub-tropical climate of South Asia

Water scarcity is becoming a major constraint for maize cultivation and increasing maize yield globally. Water-saving irrigation methods are required to increase crop water productivity (CWP) without reducing grain yield and nutrient uptake. We evaluated the effects of different methods and levels of irrigation on crop dry matter, grain yield, nutrient uptake and CWP of maize (cv. ‘BARI Hybrid Bhutta-9′) in field condition in a sub-tropical environment in Bangladesh. The experiment was laid out in a nested plot design with three replications during 2014−15 and 2015−16. The treatments were three irrigation levels (I1: 100 % field capacity, FC; I2: 80 % FC; I3: 60 % FC) and three irrigation methods (AFI: alternate furrow irrigation; SFFI: skip-fixed furrow irrigation; and TFI: traditional furrow irrigation). Results indicate that both the irrigation method and level had significant effects on dry matter, grain yield, nutrient uptake, and CWP. The AFI technique maintained similar grain yield (8.1 t ha−1) to TFI but reduced irrigation water by 37 % for irrigation applied at 100 % of FC. Both AFI and TFI had significantly higher (p ≤ 0.05) grain yield compared to SFFI at the irrigation level of I2. The interactive effect of irrigation level and method also had a significant effect (p ≤ 0.05) on maize yield. The uptakes of macronutrients (N, P, K, S, Ca, and Mg) and micronutrients (B, Zn, Fe, and Mn) by maize grain were not significantly different between AFI and TFI under I1. Irrigation level was the main driver for determining the patterns in grain yield but irrigation method controlled the patterns in CWP. The AFI technique resulted in higher CWP compared to TFI or SFFI. Results demonstrate that AFI is an effective water-saving technique, which can increase the CWP without a significant reduction in grain yield and nutrients uptake by maize grain. The AFI method in conjunction with a reduced amount of irrigation water can be adapted in the sub-tropical climates of South Asia where maize production in the dry season is heavily dependent on repeated irrigation with limited water supplies.

INNOVATIONS IN IRRIGATION SYSTEMS IN AFRICA†

INNOVATIONS IN IRRIGATION SYSTEMS IN AFRICA^†