Improve Crop Water Productivity Research Articles

Crop water stress index characterizes maize productivity under water and salt stress by using growth stage-specific non-water stress baselines

ContextThe use of non-destructive, continuous, and rapid canopy temperature (Tc) indices for crop stress diagnosis is of significant importance for improving crop water productivity (WP). However, the comprehensive applicability of the crop water stress index (CWSI), grounded in Tc, in diagnosing both single and combined water and salt stress, as well as characterizing physiological and growth traits, remains inadequately explored. ObjectiveWe aim to investigate the ability of CWSI to diagnose single and combined water and salt stress and to test whether a non-water stress baseline (NWSB) with or without growth stage and genotype differences influences CWSI to characterise maize leaf physiological and growth traits. MethodsHere, we measured the Tc using infrared radiation thermometers of two maize genotypes (XY335 and ZD958) under both single and combined water and salt stress over two growing seasons, compared the differences of NWSB in three growth stages, and established CWSI. Our analysis involved scrutinizing the differences in characterizing crop physiology and growth traits between CWSI calculated using NWSB with and without growth stage differentiations. ResultsOur findings indicated that Tc is modulated by an interplay of soil water content, VPD, and soil salinity. The NWSB exhibited variations with both growth stage (pslope < 0.001) and genotype (pslope or pintercept < 0.01). The CWSI can diagnose single and combined water and salt stress suffered by maize. Under no stress, and single and combined water and salt stress, CWSI was significantly correlated with stomatal conductance (R2 ≥ 0.31, p < 0.1) and net photosynthetic rate (R2 ≥ 0.38, p < 0.1), rather than with hydraulic traits. The mean CWSI across the entire growth period closely correlated with leaf area index (LAI), canopy photosynthetically active radiation interception, biomass, yield, and evapotranspiration across varying treatments (R2 ≥ 0.54, p < 0.1). Contrary to CWSI derived from NWSB without growth stage variations, utilizing CWSI with growth stage distinctions better characterized physiological traits, while the former was more suitable for delineating yield and WP. ImplicationsThis research underscores the efficacy of CWSI for stress diagnosis and the evaluation of gas exchange and productivity in maize under both single and combined soil water-salt stress. This investigation significantly propels forward the implementation of crop-centric irrigation strategies aimed at optimizing water utilization efficiency.

Reduced Late-Season Irrigation Improves Potato Quality, Often at the Expense of Yield and Economic Return

With a rising global population and looming water shortages in the U.S., there is a pressing need for water-efficient farming methods. The water needs of potato plants decrease in the late season due to foliage aging and tuber maturation. Therefore, proper late-season irrigation is vital in preventing water waste and maximizing potato profits. This study assessed the feasibility of reducing late-season irrigation to improve crop water productivity (WPc), tuber quality, and economic return. Field trials were planted near Othello, WA, across three years (2018–20). Treatments included five irrigation levels (ILs), 40%, 60%, 80%, 100%, and 120% of modeled evapotranspiration (ET), and five potato cultivars: Alturas, Clearwater Russet, Ranger Russet, Russet Burbank, and Umatilla Russet. Treatments started 100 to 105 days after planting (DAP), approximately 1500 day degrees (at or near peak canopy growth), and ended at vine kill, 150 to 155 DAP. Water from reduced ILs of 40% to 80% ET was more efficiently converted into yield (WPc) for Alturas than higher ILs; however, economic return for all cultivars typically peaked when irrigation was supplied at or above 80% ET. Tuber quality generally improved with a reduction in irrigation level, occasionally at the expense of yield and economic value.

Impact of calibrating a low-cost capacitance-based soil moisture sensor on AquaCrop model performance

Sensor data and agro-hydrological modeling have been combined to improve irrigation management. Crop water models simulating crop growth and production in response to the soil-water environment need to be parsimonious in terms of structure, inputs and parameters to be applied in data scarce regions. Irrigation management using soil moisture sensors requires them to be site-calibrated, low-cost, and maintainable. Therefore, there is a need for parsimonious crop modeling combined with low-cost soil moisture sensing without losing predictive capability.This study calibrated the low-cost capacitance-based Spectrum Inc. SM100 soil moisture sensor using multiple least squares and machine learning models, with both laboratory and field data. The best calibration technique, field-based piece-wise linear regression (calibration r2 = 0.76, RMSE = 3.13 %, validation r2 = 0.67, RMSE = 4.57 %), was used to study the effect of sensor calibration on the performance of the FAO AquaCrop Open Source (AquaCrop-OS) model by calibrating its soil hydraulic parameters.This approach was tested during the wheat cropping season in 2018, in Kanpur (India), in the Indo-Gangetic plains, resulting in some best practices regarding sensor calibration being recommended. The soil moisture sensor was calibrated best in field conditions against a secondary standard sensor (UGT GmbH. SMT100) taken as a reference (r2 = 0.67, RMSE = 4.57 %), followed by laboratory calibration against gravimetric soil moisture using the dry-down (r2 = 0.66, RMSE = 5.26 %) and wet-up curves respectively (r2 = 0.62, RMSE = 6.29 %). Moreover, model overfitting with machine learning algorithms led to poor field validation performance. The soil moisture simulation of AquaCrop-OS improved significantly by incorporating raw reference sensor and calibrated low-cost sensor data. There were non-significant impacts on biomass simulation, but water productivity improved significantly. Notably, using raw low-cost sensor data to calibrate AquaCrop led to poorer performances than using the literature. Hence using literature values could save sensor costs without compromising model performance if sensor calibration was not possible. The results suggest the essentiality of calibrating low-cost soil moisture sensors for crop modeling calibration to improve crop water productivity.

Comprehensive analysis of spatiotemporal variability of rainfall-based extremes and their implications on agriculture in the Upper Ganga Command Area.

The agricultural sector in India primarily relieson monsoon rains, making it necessary for agricultural water managers to study variations in water availability by analyzing rainfall patterns. This information is critical for deciding cropping patterns and irrigation approaches, managing water resources, and improving crop water productivity. The long-term spatiotemporal variability over the command area, India Meteorological Department (IMD) based selection of thresholds for extremes indices, and thorough analysis of the consequences of extreme on agriculture make the study unique. These aspects collectively enhance the perception of the climate-agriculture relationship, which is essential for promoting agriculture resilience under changing rainfall patterns. This type of research is very limited in the literature. Therefore, the present study focuses on comprehensively analyzing the spatiotemporal variability of rainfall and extreme precipitation indices and their implications on agriculture. The study is carried out in the UpperGanga Command Area (UGCA), India's oldest irrigation canal system, by using long-term (1901-2021) high-resolution (0.25 × 0.25°) daily rainfall gridded data obtained from IMD, Pune. Eight different extreme rainfall indices are used to assess spatiotemporal variations. The Mann-Whitney-Pettitt test identified 1970 as a significant change point. Rainfall trends and extreme indices for pre- and post-1970 periods were examined using the non-parametric modified Mann-Kendall test. The results show significant increases in rainfall trends for the annual, monsoon, and kharif seasons from 1901 to 1970, but significant decreases were observed during 1971-2021. This difference resulted in a noticeable decrease in average precipitation in the latter period, approximately 62mm less than in 1901-1970. Similarly, extreme precipitation indices, including the number of rainy days (NxRainy), consecutive dry days (CWD), simple daily intensity index (SDII), and total precipitation (PRCPTOT), exhibited increasing trends in 1901-1970, but they showed significant decreasing trends in 1971-2021. In addition, there is a strong positive correlation between these indices and total precipitation. The study also found that geographical factors influence these trends, with all indices, except SDII, strongly correlated with latitude and elevation, but not with longitude. The implications of these negative rainfall and extreme rainfall trends were further analyzed, and the results indicate a significant impact on the cropping patterns in the study area. The present research findings will be beneficial for regional water resource managers and policymakers in better understanding the existing trends in rainfall distribution over the UGCA.

Conventional and newly bred rootstock effects on the ecophysiological response of Vitis vinifera L. cv. Tempranillo

Achieving more environmentally sustainable vineyards, particularly regarding efficient water use, is paramount in semi-arid grape-growing regions. Rootstocks may be a possible strategy to address these challenges, but require a comprehensive evaluation of their effect on the scion, including ecophysiological traits. The objectives of this study were 1) to characterize the physiological response of Tempranillo cultivar grafted onto five commercial (1103 P, 110 R, 140Ru, 420 A, and SO4), and seven recently bred (RG2, RG3, RG4, RG6, RG7, RG8 and RG9) rootstocks and 2) to elucidate the relationships between agronomic and physiological traits conferred by grapevine rootstocks. This was carried out over three seasons (2018–2020) in a typical Mediterranean vineyard by determining water relations, leaf gas exchange, carbon isotope ratios and vegetative development and yield components. The results highlighted the different behaviour of ‘Tempranillo’ vines due to the rootstock effects on vine water status, photosynthetic performance, hydraulic conductance, vegetative growth and yield parameters. Overall, rootstocks inducing vigour and yield in the scion, such as 140Ru and RG8, showed higher leaf gas exchange rates and hydraulic conductance at the whole-plant level due to less negative water potentials, suggesting a higher water uptake and transport capacity than RG2, RG7 and RG9. The RG rootstocks showed a very wide range of ecophysiological responses, but only RG8 outperformed compared to the most widely used commercial rootstocks. Moreover, this response was modulated by the season and the block soil type, suggesting the importance of rootstock selection according to the edaphoclimatic conditions. Therefore, this study highlights the high potential of rootstocks to adapt to water scarcity by improving crop water productivity in vineyards and provides physiological insights for future studies and breeding programmes.

Design of small gravity drip irrigation for smallholder farming in water scarce region of Indonesia

Many regions in Indonesia are suffering from a water crisis due to limited annual precipitation, especially in dry regions, which affects agricultural production. Climate change is becoming more severe, threatening global food and water security. Thus, the development of affordable irrigation for smallholder farms is crucial to increasing agricultural production. The study aims to provide a better design and management of a small gravity drip irrigation system for melon cultivation. Field experiments were conducted on a farmer’s field located in Sinjai Regency to analyze the performance of the small gravity drip irrigation system on melon cultivation. The technical design was determined by analyzing the water application uniformity and irrigation water productivity. The parameters of crop growth under small gravity drip irrigation were monitored during crop development stages, and the irrigation water productivity was calculated after the crop was harvested. As a result, the small gravity drip system performed well in crop performance, and the irrigation water productivity was 1.55 kg/m3. It can be concluded that a small gravity drip irrigation system is an effective strategy for irrigating melon cultivation on smallholder farms, minimizing water loss, and improving crop water productivity.

Long-term plastic film mulching altered soil physicochemical properties and microbial community composition in Shiyang River Basin, Northwest China

Plastic film mulching (PM) is used widely to improve crop water productivity in the arid regions of Northwest China. However, there are increasing concerns about the potential harm to soil health due to the presence of residue plastic film (RPF) mixed into the soil after long-term field mulching. In our study, we investigated the density of RPF in farmland topsoil (0 to 40 cm) (Exp. I) by analyzing 75 soil samples collected from 15 fields with varying durations of PM (ranging from 3 to 27 years). In addition, we examined the impact of long-term PM and PM + BM (BM, biodegradable film mulching) on soil health (Exp. II) based on an 8-year field experiment. The results illustrated that the weight of RPF ranged from 42.7 to 165.9 kg ha−1 after 3 to 27 years of mulching, with 10 out of 15 fields exceeded the national standard of China (75 kg ha−1). Compared with no film mulching treatment (NM), the long-term PM treatment significantly increased aggregate stability, while significantly decreased soil pH and the enzymatic activities of sucrase by 1.5 % and 33.4 %, respectively. Further, the Chao1, Shannon and Pielou's indices of bacteria significantly decreased after 8 years of PM. Compared with PM and NM, PM + BM treatment significantly improved the Chao1, Shannon and Pielou's indices of bacteria and altered the relative abundance of dominant bacterial and fungal phyla. The principal coordinates analysis (PCoA) revealed significant changes in the soil bacterial and fungal community structure under PM + BM, with the soil fungal community displaying higher sensitivity to PM + BM compared to PM. No significant differences were observed in soil organic matter (SOM), soil microbial biomass C (MBC), soil microbial biomass N (MBN) contents and the enzymatic activities of soils between PM + BM and PM treatments. Overall, BM could be a promising alternative to polyethylene plastic film for improving soil health and is recommended for farming practice in the arid regions of Northwest China.

Assessment of the sustainability of groundwater utilization and crop production under optimized irrigation strategies in the North China Plain under future climate change

Over-exploitation of groundwater due to intensive irrigation and anticipated climate change pose severe threats to the water and food security worldwide, particularly in the North China Plain (NCP). Limited irrigation has been recognized as an effective way to improve crop water productivity and slow the rapid decline of groundwater levels. Whether optimized limited irrigation strategies could achieve a balance between groundwater pumping and grain production in the NCP under future climate change deserves further study. In this study, an improved Soil and Water Assessment Tool (SWAT) model was used to simulate climate change impacts on shallow groundwater levels and crop production under limited irrigation strategies to suggest optimal irrigation management practices under future climate conditions in the NCP. The simulations of eleven limited irrigation strategies for winter wheat with targeted irrigations at different growth stages and with irrigated or rainfed summer maize were compared with future business-as-usual management. Climate change impacts showed that mean wheat (maize) yield under adequate irrigation was expected to increase by 13.2% (4.9%) during the middle time period (2041–2070) and by 11.2% (4.6%) during the late time period (2071–2100) under three SSPs compared to the historical period (1971–2000). Mean decline rate of shallow groundwater level slowed by approximately 1 m a−1 during the entire future period (2041–2100) under three SSPs with a greater reduction for SSP5–8.5. The average contribution rate of future climate toward the balance of shallow groundwater pumping and replenishment was 62.9%. Based on the simulated crop yields and decline rate of shallow groundwater level under the future climate, the most appropriate limited irrigation was achieved by applying irrigation during the jointing stage of wheat with rainfed maize, which could achieve the groundwater recovery and sustainable food production.

Abscisic acid agonists suitable for optimizing plant water use.

Climate change and overexploitation of groundwater resources cause constraints on water demand for agriculture, thus threatening crop productivity. For future food security, there is an urgent need for crops of high water use efficiency combined with high crop productivity, i.e. having high water productivity. Highwater productivity means efficient biomass accumulation at reduced transpiration. Recent studies show that plants are able to optimize carbon uptake per water transpired with little or no trade-off in yield. The phytohormone abscisic acid (ABA) plays a pivotal role in minimizing leaf transpiration and mediating enhanced water productivity. Hence, ABA and more chemically stable ABA agonists have the potential to improve crop water productivity. Synthesis, screening, and identification of suitable ABA agonists are major efforts currently undertaken. In this study, we used yeast expressing the plant ABA signal pathway to prescreen ABA-related cyano cyclopropyl compounds (CCPs). The yeast analysis allowed testing the ABA agonists for general toxicity, efficient uptake, and specificity in regulating different ABA receptor complexes. Subsequently, promising ABA-mimics were analyzed in vitro for ligand-receptor interaction complemented by physiological analyses. Several CCPs activated ABA signaling in yeast and plant cells. CCP1, CCP2, and CCP5 were by an order of magnitude more efficient than ABA in minimizing transpiration of Arabidopsis plants. In a progressive drought experiment, CCP2 mediated an increase in water use efficiency superior to ABA without trade-offs in biomass accumulation.

Alternative Techniques of Irrigation Water Management for Improving Crop Water Productivity

Alternative Techniques of Irrigation Water Management for Improving Crop Water Productivity

Optimizing crop water productivity and altering root distribution of Chardonnay grapevine (Vitis vinifera L.) in a silt loam soil through direct root-zone deficit irrigation

The potential for sustaining grape production and improving crop water productivity in semi-arid areas through direct root-zone irrigation (DRZ) has been demonstrated in recent studies; however, it has only been tested for red wine grapes in sandy soils. To expand its application, a field study was conducted to investigate the influences of DRZ with reduced irrigation rate on yield, berry quality, root growth, plant water status and crop water productivity of white wine grape Vitis vinifera L. cv. Chardonnay grown in a silt loam soil within a semi-arid region of Washington state, USA. Compared with the surface drip irrigation which has been applied for decades in the study area, DRZ could improve the crop water productivity by 23 – 34 % and reduce the irrigation amount by 16 – 23 % without yield loss under variable weather conditions, indicating the efficacy of the DRZ as a novel subsurface irrigation strategy. Concurrently, DRZ restricted root distribution within 0 – 60 cm soil layers, and significantly reduced root number and root length density were observed in 20 – 40 cm soil depth. Moreover, grapevines under moderate water stress induced by DRZ accumulated more soluble sugar (8.8 % increase in °Brix on average) and yeast assimilable nitrogen (24.4 % increase on average) in berries. We conclude that proper deficit irrigation applied through DRZ would be applicable to optimize the water use for production and efficiently alter the root distribution pattern of Chardonnay grapevine cultivated in moderately permeable soils with improved berry quality.

Cost-effective strategies to improve crop water productivity—case study: Bakhtegan and Maharloo, Iran

Cost-effective strategies to improve crop water productivity—case study: Bakhtegan and Maharloo, Iran

Bibliometric and Visual Analysis of Crop Water Footprint: A Widely Used Agricultural Water Resources Evaluation Method

As a new theme in agricultural water resources evaluation, the crop water footprint (CWF) has attracted much attention, and the number of published studies has shown rapid growth. In order to explore the research prospects of the CWF, this paper conducted a visual bibliometric analysis of its development context, hot topics and knowledge base, by using CiteSpace (version 5.6. R5, Chaomei Chen, Philadelphia, PA, USA). Up to the retrieval time, there were, in total, 838 articles based on the Web of Science core collection database. In terms of contribution, China, the Netherlands and the United States were the three most representative countries, and the University of Twente and Arjen Y. Hoekstra were the most productive institution and author, respectively. In terms of the discipline background, Environmental Sciences &amp; Ecology, Environmental Sciences and Water Resources were the three most relevant categories. Based on the co-occurrence analysis of the keywords, the hot topics of the three periods has been illustrated, and assessing the climate change impact on the water-use efficiency of crop production is the focus of the current research. The knowledge background of the CWF was elaborated by the co-citation and cluster analysis of references, which consists of four parts: concept, quantification, evaluation and reduction. Reducing the water requirement to improve crop water productivity through rainwater harvesting and formulating reasonable hydro-policies is the main responsive strategy to improve agricultural water-use efficiency. In particular, the accurate differentiation of the blue, green and gray water footprint calculation, considering multiple pollutants, the exploration of mitigation policies for the climate change impact and the combination of the CWF and traditional indicators, will be the focuses of future research in the CWF.

Proposing a combined method for the estimation of spatial and temporal variation of crop water productivity under deficit irrigation scenarios based on the AquaCrop model

Deficit irrigation is a management strategy to improve crop water productivity, especially in arid and semi-arid regions. Soil characteristics and weather parameters are among the factors affecting crop water productivity in water stress conditions. Due to spatial changes in soil characteristics and temporal and spatial variations in meteorological parameters, it can be expected that crop water productivity will also have temporal and spatial variations. In this study, by combining the Geographic Information System (GIS) with the grid weather generation tools from the Crop Growth Monitoring System (CGMS) and the plug-in version of the AquaCrop, a combined method was developed to investigate the spatial and temporal variation of crop yield, seasonal crop evapotranspiration, and water productivity of maize under various irrigation scenarios. The proposed model was implemented in a case study in the west of Iran. The study area was divided into 37 grid weather with 5 * 5 km and 19 soil units. By overlaying soil units and grid weathers, 94 homogeneous units were created. The model was executed for 94 homogeneous areas, using calibrated crop file of grain maize under four irrigation scenarios of 40, 60, 80, and 100% of potential irrigation requirement (S40, S60, S80, and S100, respectively) for 28 years (1988–2015) of weather data (10,528 runs). The results showed that by increasing water stress, the percentage of spatial and temporal variation of the studied parameters (crop yield, seasonal crop water requirement, and water productivity) would be increased. The percentage of spatial changes in crop yield and crop water productivity was more significant than temporal changes. The average of crop water productivity in the scenarios of S100, S80, S60, and S40 was determined as 1.5, 1.4, 1.2, and 0.5 kg m−3, respectively.

How does plastic film mulching affect crop water productivity in an arid river basin?

Plastic film mulching is a widely used and effective field practice to improve crop water productivity (CWP), especially in arid and semiarid areas. The positive effects of soil mulching on crop yields and CWP have been studied through numerous field experiments and simulations at the site scale. However, few studies have focused on assessing mulching effects at the regional scale. The Zhangye Basin, a typical arid region in the middle Heihe River Basin of northwest China, was chosen as the focus of the present study. The AquaCrop model, a water-driven crop growth model, was first calibrated and validated using field observations from three experimental stations and extended to the regional scale by considering the spatial heterogeneity of soil, meteorology, crop characteristics, irrigation treatment and land use change. Three mulching practices under current irrigation schedules were simulated in the well-validated model for a 20-year period (1995–2015). The results showed that plastic film mulching conserved soil water and significantly reduced nonproductive evaporation. Crop transpiration and yield were enhanced while evapotranspiration decreased under mulching. Compared to no mulching, half-film mulching and major film mulching with 70% coverage effectively improved CWPs at the regional scale, with respective average increases of 7.2% ± 0.9% and 14.1% ± 2.2% for seed maize and 4.1% ± 0.7% and 7.8% ± 1.0% for spring wheat. The results demonstrated that the impacts of plastic film mulching on CWP varied with crop type and location in relation to water input. The regional evaluation also identified one particular area (Ganzhou) as the most suitable to apply plastic films, especially to seed maize. This study offers a better understanding of agronomic practices and helps improve CWP more effectively, ultimately contributing to water savings and food security in arid regions.

Mulching optimizes water consumption characteristics and improves crop water productivity on the semi-arid Loess Plateau of China

Water consumption is closely related to crop growth and development, and optimizing its characteristics will be beneficial to water saving and high yield of crops. To find out the more promising cultivation technology to optimize water consumption characteristics and improve crop water productivity for winter wheat, a four-year field experiment in 2015–2019 was conducted in a randomized and complete block design in the Loess Plateau of northwest China. The experimental treatments: (i) whole plastic-film mulching (PFM), coverage rate was approximately 100%, (ii) straw strips mulching (SSM), including the alternating straw strip (0.5 m) and plant strip (0.35 m), and the coverage rate was 59%, (iii) conventional flat planting without mulching (CK). The obtained results showed that PFM and SSM increased the contribution rate of precipitation to evapotranspiration; inhibited evaporation but promoted transpiration to a great extent; reduced soil water storage consumption in the 0–60 cm but promoted it in the 150–200 cm soil layer; reduced soil water storage consumption at the early growth stage but promoted it at the middle growth stage compared with CK. In 2015–2019, compared with CK, PFM and SSM respectively decreased soil water consumption by 12.4% and 10.6% in the 0–60 cm soil layer, but increased it by 46.6% and 27.7% in the 150–200 cm soil layer. PFM and SSM reduced evapotranspiration by 20.1% and 14.4% before the jointing stage due to the low water consumption intensity, but increased it by 26.8% and 11.1% from jointing to blooming stage due to the high water consumption intensity. Besides, PFM and SSM respectively improved crop water productivity by 20.1% and 19.1%, improved precipitation use efficiency by 20.0% and 18.6%, and eventually increased grain yield by 18.1% and 16.5%. SSM was less effective than PFM, but taking the friendly sustainability into consideration, SSM would probably be a potential practice to develop the rainfed agriculture.

Soil Moisture based Automatic Irrigation System to Improve Water Productivity

Irrigation automation plays a vital role in agricultural water management system. An efficient automatic irrigation system is crucial to improve crop water productivity. Soil moisture based irrigation is an economical and efficient approach for automation of irrigation system. An experiment was conducted for irrigation automation based on the soil moisture content and crop growth stage. The experimental findings exhibited that, automatic irrigation system based on the proposed model triggers the water supply accurately based on the real-time soil moisture values.

Implications of Adopting Drip Irrigation System on Crop Yield and Gender-Sensitive Issues: The Case of Haramaya District, Ethiopia

Integration of advanced irrigation systems and technology is essential to improve crop water productivity and yields, especially in developing countries. This study aims at investigating the effects of adopting a drip irrigation system combined with hand-dug wells on crop water productivity and yields of household farmers and their perception on the proposed scheme over two cropping seasons in the Haramaya District, Ethiopia. We chose three locally called “Kebeles” within the District, and selected a certain number of household farmers that had similar characteristics within each Kebele. The selected farmers had practiced both the proposed drip irrigation with private hand-dug wells water supply (intervention pilots) and traditionally-used surface irrigation with communal water supply (non-intervention pilots) schemes. We also conducted interviews with the selected household farmers, personal observations, and measurements on crop water productivity and yields for both intervention and non-intervention pilots. We found that the proposed drip irrigation system significantly improved the crop productivity and yields of the farmers. More importantly, findings indicated that the use of drip irrigation system combined with hand-dug well water supplies reduced the over-exploitation of water (water savings) and labor-intensive manual-irrigation. The latter particularly helped women to work less on their farm works and thus provided them a flexible system to expand their plot sizes and grow a variety of crops. Overall, the drip irrigation system with water supply from hand-dug wells is highly recommended as it allows a flexible system for household farmers and provides an opportunity to expand their plot sizes with a variety of crops, which is also expected to mitigate the negative implications of climate change on freshwater water resources and crop productivity. However, the farmers of the Haramaya District expressed their need on capacity building, financial and technical supports from local to regional governments and other agencies to ensure an efficient and cost-effective drip irrigation system and to further improve their crop water productivity and yield, food self-sufficieny, and livelihoods. It is also important to consider market-based farming approaches, while promoting efficient irrigation systems and self-supply to ensure quick investment returns. This study recommends to adopt and expand the proposed drip irrigation system at household levels in Sub-Saharan and other similar regions.

Optimizing the planting density under the ridge and furrow rainwater harvesting system to improve crop water productivity for foxtail millet in semiarid areas

The ridge and furrow rainwater harvesting (RFRH) planting system has many advantages for improving the use of water during dryland farming in semiarid areas, but the optimally matched planting density for maximizing the productivity of foxtail millet is not known. Therefore, field experiments were conducted during 2013–2015 to determine the soil water content with depth, evapotranspiration (ET), agronomic traits, grain yield, and crop water productivity under different planting densities when using RFRH planting (width of ridge and furrow is 60 cm, three rows were planted in furrow) compared with traditional flat planting. The results show that a high planting density would lead to soil drought conditions in the late reproductive growth stage, with reductions in individual plant traits and the harvest index (HI) in dry years. However, we found that RFRH planting could reduce ET and improve the soil water content at 0-120 cm soil layers in the jointing and filling stages, as well as mitigating the crop water deficit in the reproductive growth stage and the decreased HI caused by a high planting density. Compared with traditional flat planting, RFRH planting decreased the foxtail millet grain yield in the rainy year (2013) due to the relatively lower plant population, but it increased the yield in the normal rainfall years of 2014 and 2015, as well as significantly improving the crop water productivity by 7.9% and 14.0% under the optimized planting density, respectively. A relatively higher optimal planting density was always obtained in the furrows under RFRH planting compared with traditional flat planting in all three experimental years. Based on these results, we recommend increasing the planting density in the furrows to increase the grain yield and crop water productivity under RFRH planting, with a moderate planting density for foxtail millet (three rows in a 60 cm wide furrow and a plant spacing of 7.5 cm) in semiarid regions of China.

INNOVATIONS IN IRRIGATION SYSTEMS IN AFRICA†

INNOVATIONS IN IRRIGATION SYSTEMS IN AFRICA^†