Water-saving Irrigation Practices Research Articles

Mapping irrigation regimes in Chinese paddy lands through multi-source data assimilation

Water-saving irrigation (WI) is a crucial agricultural management with the benefits to save irrigation water, reduce energy consumption, and suppress methane emissions from paddy lands. Classifying WI practices from traditional flooding irrigation (FI) is a key component in detecting the rice irrigation status, which is significant to estimate the total agriculture-associated greenhouse gas emissions. In this study, we developed an automatic method to map irrigation regimes across Chinese paddy lands. First, we used seven variables related with irrigation facility or vegetation cover as proxy to generate representative WI and FI samples. Besides, we composited 123 features of optical bands and synthetic aperture radar from MODIS and Sentinel-1 data. Then, we trained a random forest model for each province with these samples. Finally, we applied the trained model to generate maps of WI/FI practices at 500m resolution. Comparisons of the resultant maps with census data indicated highly accurate estimations of the WI area at a city- or province-level, with a R2 higher than 0.92. The overall accuracy of the classification was approximately 0.73, as validated through ground truth samples. Additionally, we also conducted a data quality analysis and confirmed the classification results were reliable in main rice production area of China. With the push towards carbon neutrality goals and the increasing demand for clean management practices, we developed and demonstrated an advanced method to produce near real-time maps of irrigation regimes and provide crucial data support for agricultural emissions reduction and irrigation management decisions.

Enhancing growth and tolerance traits in pepper (Capsicum annuum L.) through water-saving irrigation practices

Due to their intensive cultivation, horticultural crops are particularly susceptible and vulnerable to the detrimental effects of drought stress, necessitating significant water inputs for optimal growth and yield. Accordingly, water-saving irrigation strategies, i.e., Partial Root zone Drying (PRD) and Regulated Deficit Irrigation (RDI) emerge as pivotal tools for bolstering the resilience of the horticultural sector. The current study aims to evaluate the impact of PRD and RDI strategies on pepper (Capsicum annuum L.) growth, and physio-biochemical attributes under semi-controlled greenhouse conditions. Research findings revealed pronounced enhancements in stem length under both irrigation strategies, with PRD exhibiting superior effects on shoot fresh and dry biomass (increases of 57.2% and 61.1%, respectively) compared to full irrigation. At the physiological level, PRD and RDI induced a significant reduction in stomatal conductance in pepper plants relative to full irrigation, while maintaining leaf water potential and relative water content. Biochemically, plants subjected to PRD and RDI methods exhibited significant accumulation of free proline, particularly pronounced with PRD (approximately 115.9% increase compared to full irrigation). Furthermore, Chl a and carotenoid concentration significantly increased under PRD, indicating sustained photosynthetic functionality. Comparatively, PRD appears as the more effective technique, offering the potential to conserve agricultural water about 50 without compromising growth parameters, while simultaneously enhancing tolerance traits in C. annuum. Nonetheless, further investigations on other traits across diverse soil types, climates, and cultivars under field conditions are imperative to ascertain the broader applicability of PRD and optimize its implementation.

Rice yield and water productivity in response to water-saving irrigation practices in China: A meta-analysis

Various water-saving irrigation (WSI) practices (e.g., dry cultivation, intermittent irrigation, controlled irrigation, shallow-wet irrigation, and rain-gathering irrigation) have been applied to rice cultivation mitigate water scarcity in China. However, in previous studies, these WSI practices have shown different water savings and yield increases, mainly due to different application conditions. A meta-analysis was applied to investigate the responses of the actual evapotranspiration (ETact), irrigation water (IW), rice yield (Y), and water productivity (WP) to WSI practices in different conditions, and 956 data sets were selected from 108 published papers. The results showed that, compared to traditional flood irrigation, rain-gathering irrigation decreased ETact and IW by 25.41 % and 55.7 % respectively, and increased WP greatly by 14.26 % while having a slight decrease in Y. Except for dry cultivation, all WSI practices increased WP by 4.72–14.26 % compared to traditional flood irrigation. The effects of different soil qualities on rice water consumption and production vary; medium soils with high organic content and a pH below 6.5 are better for rice growth. As for rice seasons, WSI practices had the least impact on ETact in middle rice, with an average reduction of 5.84 %, followed by early rice (–12.66 %) and late rice (–18.81 %). Higher mean annual temperature and more precipitation led to more Y under WSI practices. Differences in the effects of mean annual temperature and mean annual precipitation on WP were not significant. Our meta-analysis provides more insight into the effects of water-saving irrigation practices on rice water consumption, yield, and water productivity at various experimental sites. In general, there is considerable variation in the responses of Y and WP to different water-saving irrigation practices, and more evaluation of aspects such as rice seasons, soil properties, and meteorological conditions is needed for optimizing WSI in practice.

A bibliometric analysis of scientific literature on alternate wetting and drying (AWD)

The study presents a bibliometric analysis of scientific literature on alternate wetting and drying (AWD) as a water-saving irrigation practice for rice cultivation. Data were collected from the Web of Science, resulting in a database of 439 articles written by 2574 authors in 167 journals. The study reveals the growing importance of AWD in publications from the 90s to mid-2022, with fast growth and reaching its peak in the last 5 years, suggesting that the full potential of AWD remains yet to be realised and explored. Most papers are produced in oriental countries, except the USA and Australia. The trend of keywords in the research on AWD reveals a persistence of certain themes throughout the years while simultaneously showcasing a clear evolution of the topics being addressed. In addition to optimising productivity and agricultural yields, research now encompasses environmental issues and human and crop health, reflecting a broader trend in agriculture and research towards sustainable and environmentally responsible practices. This analysis provides insights into the development and direction of research in AWD, emphasising the need for future research to address the emerging concerns of the impact of AWD on the environment, human and crop health, and economic profitability of AWD adoption.

Evaluating the Performance and Opportunity Cost of a Smart-Sensed Automated Irrigation System for Water-Saving Rice Cultivation in Temperate Australia

Irrigated rice is the largest user of precious global water reserves. Adoption of water-saving irrigation practices is limited by the associated increased labor demand compared to flooded rice cultivation. Automated gravity surface irrigation systems have shown the potential to deliver significant labor savings in traditional flooded rice; however, widespread adoption does not seem apparent. Furthermore, previously designed systems have not been capable of irrigation control during both ponded and non-ponded periods. This study aimed to evaluate the performance of an automated irrigation system for rice with features not previously developed, provide direction for future systems and analyze the opportunity cost (the value of other on- or off-farm activities that could be conducted with that time) of time associated with automated irrigation. The automated irrigation system was found to successfully control 23–31 flush-irrigation events per bay per season in a 9-bay border-check aerobic rice field for 2 seasons. In addition, successful water control was achieved in a traditional drill-sown field with 4 flush irrigations followed by 15 weeks of permanent flooding. Labor savings of 82–88% during the flush-irrigation events and 57% during the ponding period were achieved with automation when compared to manual irrigation. However, the opportunity cost of the saved time was found to comprise the greatest benefit. Changing the analysis from using a flat “cash” cost of time to using opportunity cost of time reduced the payback period from seven to four years at the traditional ponded-rice site. In the more labor-intensive aerobic rice site, the payback period was reduced from three years to one year when accounting for the opportunity cost of time as opposed to only the direct costs. Whilst the payback period is site-dependent and cultivation method-dependent, these case studies demonstrate that automated gravity surface irrigation can enable novel water-saving practices in rice and provide substantial economic benefits.

Spatiotemporal Characteristics and Hazard Assessments of Maize (Zea mays L.) Drought and Waterlogging: A Case Study in Songliao Plain of China

The Songliao Plain is the largest maize (Zea mays L.) cropland area in China and, thus, is most influenced by water stress. To mitigate the adverse impact of water stress on maize yield and quality, various agricultural irrigation strategies have been implemented. Based on land surface temperature and an enhanced vegetation index, this study constructed the temperature vegetation dryness index (TVDI) and combined the Hurst index and Sen trend to analyze the spatiotemporal characteristics of drought and waterlogging. From the correlation between TVDI and gross primary productivity, the weight coefficients of different growth cycles of maize were derived to determine the drought and waterlogging stresses on maize in Songliao Plain for 2000–2020. The drought hazard on the western side of Songliao Plain was high in the west and low in the east, whereas the waterlogging hazard was high in the east. Waterlogging likely persisted according to the spatiotemporal trends and patterns of drought and waterlogging. During the second growth cycle, maize was most severely affected by water stress. There was a spatial heterogeneity in the severity of the hazards and the stress degree of maize. For the reason that precipitation in the study area was concentrated between mid-late July and early August, maize was susceptible to drought stress during the first two growth stages. Irrigation concentrated in the early and middle stages of maize growth and development in the western part of the Songliao Plain reduced the drought stress-induced damage. Spatiotemporally-detected drought and waterlogging couplings and hazards for maize in the Songliao Plain for 2000–2020 provide actionable insights into the prevention and mitigation of such disasters and the implementation of water-saving irrigation practices at the regional scale.

Effect of Soil Moisture Deficit on Aerobic Rice in Temperate Australia

Declining water availability is pressing rice growers to adopt water-saving irrigation practices such as aerobic rice to maintain profitability per megalitre (ML) of water input. Irrigators require well-defined irrigation thresholds to initiate irrigation to maximise water productivity. Such thresholds do not exist for temperate rice regions. Adopting a strategy that has been reported to succeed in non-temperate environments may fail in temperate climates, and therefore, needs investigation. This study aimed to investigate, in a temperate Australian environment, the effect of increasing soil moisture deficit during the rice vegetative period on crop physiological development, grain yield and water productivity. The study was conducted in a commercial farm using a randomised complete block design in the 2020/21 and 2021/22 growing seasons. Automated gravity surface irrigation technologies were adopted to enable high-frequency irrigation. Extending soil moisture deficit beyond 15 kPa was found to significantly delay panicle initiation by at least 13–14 days, exposing rice to cold temperatures in Year 1 during the cold-sensitive early pollen microspore period. This reduced yield by up to 55% (4.5 t/ha) compared to the 15 kPa treatment that was not impacted by cold sterility. In the absence of cold sterility, irrigated water productivity and total water productivity ranged between 1.02 and 1.61 t/ML, and 0.84 and 0.93 t/ML, respectively. The highest yields (8.1 and 7.5 t/ha) were achieved irrigating at a soil tension of 15 kPa in growing seasons 2020/21 and 2021/22. This research demonstrates that sound water productivity can be achieved with aerobic rice cultivation in temperate climates, providing cold temperatures during early pollen microspore are avoided. The quantification of the delay in crop development caused by increasing soil moisture deficit provides rice farmers greater confidence in determining the irrigation strategy and timing of pre-emergent irrigation in regions at risk of cold sterility. However, due to the high labour demand associated with aerobic rice, the adoption of aerobic rice at a commercial scale in this Australian environment is unlikely without adopting automated irrigation technology.

Spatio-Temporal Evolution of the Ecological Environment in a Typical Semi-Arid Region of Northeast China

Increasing trends of groundwater and soil salinization, as well as desertification, is characteristic of many arid and semi-arid regions under climatic and anthropogenic influences. This has led to the implementation of management strategies to protect the ecological environment. Changling County in Northeast China is a typical semi-arid area that has experienced these changes. Thus, management strategies such as the “Three North Shelterbelt Project” which involves planting trees to reduce wind speed and halt desertification, and the Changling local alkaline land restoration project, from the year 2000, involving fencing of grasslands have been implemented in the area. Premised on the dynamic nature of the ecological environmental problems, this study was undertaken to assess the spatio-temporal evolution of the ecological environment using hydro-geochemical, spatial, remote sensing, and statistical techniques from the year 2001 to 2019. It was found that groundwater salinity was stable within the period due to groundwater exploitation that declined depth to groundwater table (DWT) thus reducing the impact of evaporation concentration of salts in groundwater. Salinized land area increased by about 6706 ha at a rate of 0.06%/year as a result of the reduction in the size of water bodies and swampland as the declining water table exposed shallow water to more evaporation. The effect of the conversion of water bodies and swamplands to salinized land is believed to overshadow the climatic influence of decreased evaporation-precipitation ratio that normally decreases soil salinization. Most of the study area was stable in terms of desertification (98.22%, 56,3497 ha) as significantly degraded lands covered only 0.03% (148 ha) of the area while 1.67% (9556 ha) had significantly increased vegetation, respectively. Precipitation had an insignificant relationship with desertification with irrigation believed to be the main driver of significant vegetation improvement. Water-saving irrigation practices and the growing of salt-tolerant or semi-tolerant crop species are recommended to maximize food production while stemming the environmental degradation trend due to declining DWT.

Assessment of the AquaCrop Model under different irrigation scenarios in the North China Plain

Crop simulation models play an essential role in evaluating irrigation management strategies for improving agricultural water use in crop production. In this study, the AquaCrop model was used to calibrate and validate the grain yield and biomass of 11 cultivars (9 winter wheat and 2 summer maize) under full and water-saving irrigation practices. The model results were verified with the available data from the published literature. Under the full irrigation practice, widely used by farmers in the region for winter wheat, the Normalized Root Mean Square Error (NRMSE) was found to be between 2.00–9.90% for grain yield, 2.40–10.85% for biomass, and 0.42–19.61% for water productivity. Under water-saving irrigation for winter wheat, the NRMSE range was found to be between 5.80–16.00% for grain yield, 3.70–17.30% for biomass, and 3.80–13.79% for water productivity. For summer maize, the NRMSE was 5.95%, 6.08%, and 16.41% under full irrigation, and 9.51%, 8.41%, and 3.60% under water-saving irrigation for grain yield, biomass, and water productivity, respectively. For winter wheat and summer maize, the simulation accuracy of grain yield was high under full irrigation, with percent deviations under ± 11.00%. In this study, the simulation accuracy for winter wheat was low under water-saving irrigation, while the model simulated the yield and biomass for summer maize to acceptable accuracy. The model can be reliably used as a tool to simulate grain yield and biomass across the NCP region for winter wheat and summer maize. However, the limitations of the model must be considered when simulating winter wheat under water-stressed conditions.

The Role of Farm Ponds in Agricultural Development: A Case Study of Nivadunge Village in Pathardi Tehsil of Ahmednagar District (M.S.)

Farm ponds have been built all over the world to encourage agricultural expansion. Natural-based solutions are increasingly being recognized as a viable option for addressing water-related issues. This is the first study to look at how ponds influence the adoption of water-saving irrigation practices. Sustainable rural development and the management of other small, scattered wetlands can benefit from the conservation advice and analytical methodology. The current study examines agricultural improvement in Nivadunge village using farm ponds. The evolution of agriculture was tracked using a variable parametric method. This village is situated in a drought-prone region. The depth of black cotton and red soil is shallower than that of other soils. There are gravel and sandy soil types, and they store water to a lower extent. This type of research can help villages grow their agriculture in a holistic way.

Economic Evaluation of Water-Saving Irrigation Practices for Sustainable Sugarcane Production in Guangxi Province, China

Impact of climate change on sugarcane (Saccharum spp. interspecific hybrids) crop growth, development and productivity remains unclear globally. In China, the per capita available water resource amounts to only 1/4th of the global average. The limited water is one of the most significant constraints for sustainable agriculture development and crop productivity in China, and thus water-saving irrigation technology can reduce the seasonal water shortage in agricultural crop production, improve crop yield and quality, and enhance sustainable agricultural crop development. Keeping this in view, we conducted a field experiment at Guangxi sugarcane-growing hilly dry land with steep slope from 2017 to 2020 in plant and two ratoon crops. Results showed that bud germination (%), tillering rate, plant height and millable cane were not significantly different in spray and drip irrigation treatments. As compared to control, spray irrigation and drip irrigation (DI) remarkably increased the crop growth and yield. Drip irrigation produced a significantly higher cane production, consumed less irrigation water (65%) and provided maximum irrigation water use efficiency. Our study suggested that DI was far more effective in conserving water for irrigation and could be recommended and adopted in Guangxi and similar crop production regions.

Adaptation of resilient regenerative agricultural practices by small-scale growers towards sustainable food production in north-central Arizona

The demand for agricultural lands for other uses because of population growth and extreme climate in Arizona led to 57% decrease in average farm size and 127% increase in farm numbers from 1997 to 2017, which threaten sustainable local food production. Small-scale family farms of less than 10 acres make up 50% of the farmer population in the state and have a vital role in resilient and sustainable practices that maximize land use with less negative impact on the environment. This study investigated land use and farm practices among small-scale growers in north-central Arizona in their resilience in sustainable food production. The finding revealed 52% of the small farms are family operations with dominant regenerative and sustainable practices (27% cover cropping, 26% compost, 23% crop rotation, 22% animal and green manure, 21% no-till, and 18% reduced tillage) with less interest in conventional practices (5% intensive tillage and 13% synthetic fertilizers). Ninety-five percent of the growers used biological, cultural, or mechanical practices for weed, pest, and disease control, while only 5% used conventional synthetic chemicals. For water use, 78% of the growers used water-saving irrigation practices (drip, subsurface, and sprinklers), while 11% used open flood irrigation. Driving forces for the sustainable practices among the small-scale growers are their consumers (community supported agriculture, restaurants, Farmers' Markets, and farm stands) and extreme climate conditions. Small-scale growers have great potential in advancing resilient, environmentally friendly practices for sustainable local food production and environmental stewardship.

Influence of alternate wetting and drying water-saving irrigation practice on the dynamics of Gallionella-related iron-oxidizing bacterial community in paddy field soil

The redox cycle of iron (Fe) is a key process in the biogeochemistry of paddy field soil. It has been recently remarked that Fe(II)-oxidizing bacteria belonging to the family Gallionellaceae (Gallionella-related FeOB) are one of the key players in the Fe(II) oxidation in the soil. The present study aimed to investigate the influence of alternate wetting and drying (AWD) irrigation for water-saving rice cultivation on the dynamics of the community of Gallionella-related FeOB in the paddy field soil over three seasons (wet-dry-wet seasons) of rice cultivation. The AWD irrigation brought about the reduction of Fe(II) contents in the soil, compared with the continuously flooding (CF) irrigation, especially in the last half of the rice cultivation period in the dry season. In contrast, a trend of higher copy number of 16S rRNA genes of Gallionella-related FeOB was observed in the last half of the rice cultivation period of the AWD paddy soil. As a result, a significant negative correlation was observed between the Fe(II) contents and the copy numbers of 16S rRNA genes. PCR-DGGE analysis of 16S rRNA genes of Gallionella-related FeOB showed that the band patterns were different between the CF and AWD paddy soils. Meanwhile, the results of clone library analysis indicated that differences in the taxonomic composition of Gallionella-related FeOB were not observed between the CF and AWD paddy soils, suggesting that Gallionella-related FeOB responded to the AWD water-saving irrigation on the individual strain levels. The potential of Fe(II)-oxidizing activity and its apparent contribution of the activity of Gallionella-related FeOB to the Fe(II) oxidation in the soil of the investigated field were estimated to be 2.4 × 10−3 to 1.7 × 10−1 mg Fe(II) g−1 dry soil day−1 and 4.6%, respectively, based on the reported Fe(II) oxidation rates of cells. The present study showed that the fluctuation of the redox status of Fe caused by the repeated cycle of wetting and drying of the field brought about the changes in the community structure of Gallionella-related FeOB in the soil. Furthermore, it was suggested that Gallionella-related FeOB were certainly involved in the Fe(II)-oxidizing process in the AWD paddy field soil.

Modeling rice evapotranspiration under water-saving irrigation condition: Improved canopy-resistance-based

Models capable of accurately calculating crop evapotranspiration (ET) are essential to improving water management at both the hydrological cycle and the agriculture irrigation project scale. Penman-Monteith (PM) and Shuttleworth-Wallace (SW) models based on the Jarvis-type canopy resistance (rc) model were used to calculate the hourly and daily ET of rice grown in East China under water-saving irrigation (WSI). The model parameters in rc and soil resistance (rss) were recalibrated to improve the accuracy of rice ET estimations. Notable, three improvements were made to the rc model: (i) model parameters were calibrated at the canopy scale, and a term of effective leaf area index was used to reflect the influence of canopy coverage; (ii) the coefficient a4 was used to reflect the influence of the specific soil moisture patterns under WSI practice; and (iii) for rice crops, soil moisture at saturation, rather than at field capacity for upland crops, served as a key parameter in the soil water response functions. Both PM and SW models generated similar rice ET outputs due to their common theoretical basis. Surprisingly, the PM model, with an appropriately adjusted rc value, performed better than the SW model in simulating hourly and daily rice ET under WSI practice, particularly during periods when canopy cover was either dense or sparse. Sensitivity analyses showed both models to be highly sensitive to changes in rc, and soil moisture (θ), the latter being one of the dominant contributors to variations in rc and rss. Accordingly, the PM model is recommended for the prediction of rice ET grown under WSI conditions in East China, with the caveat that both the rc and θ should be accurately quantified when used as inputs.

Developing a methodology for estimating the groundwater levels of coastal aquifers in the Gareb-Bourag plains, Morocco embedding the visual MODFLOW techniques in groundwater modeling system

The objectives of this work are to control the groundwater levels of the coastal aquifer of Gareb-Bouareg from Rif Morocco using Visual MODFLOW techniques, as part of the Groundwater Modeling System (GMS 7.0), to bring the water table back to safety limit and to prevent any further rise of this water table. However, the calibrated and validated model makes it possible to carry out several scenarios whose objective is to test the impact of various modes of exploitation on the water table in an area suffering from waterlogging problems, such as the case of the Gareb-Bouareg aquifer from Morocco. The results obtained according to the optimal and realistic scenario made it possible to lower the piezometric level of 5.42 m over an area of 14 km2 by applying a pumping of 300 L/s on 10 wells with a flow rate of 30 L/s/well. This technique could be improved by reducing inputs through water-saving irrigation practices or by applying corrective measures to increase the outflows that will eventually be demineralized and exploited for drinking water consumption.

Groundwater modeling in the Mediterranean area: case of the Gareb-Bouareg coastal aquifer (Rif, Morocco)

The Gareb-Bouareg aquifer is located in northeastern Morocco. This aquifer extends continuously and expansively under the two plains of Gareb and Bouareg. The introduction of irrigated agriculture utilizing only surface water to these plains has resulted in an alarming rise in the level of the water table, leading to waterlogging and salinization, which have adversely affected crop growth and rendered large areas of the plains unproductive. Therefore, a study of the water-table fluctuations in response to the agricultural development of this area was carried out. Two potential methods of lowering the water table of the brackish alluvial aquifer—the installation of subsurface and deep drainage networks—were proposed. Due to a lack of sufficient data at the local scale (agricultural parcels), it was not possible to simulate the functioning of the agricultural drainage system, so a regional MODFLOW model based on a hydrodynamic modeling approach was used to determine the optimal method of lowering the groundwater level and preventing it from rising above safe levels, thus preserving the quality of the soil and improving growing conditions for crops. After successful calibration and validation of the model, several pump-draining scenarios were simulated to evaluate their impacts on the water table in an area of the plains that suffers from waterlogging. The results for the most realistic scenario revealed that pump draining performed via 10 wells at a rate of 30 l/s per well (i.e., 300 l/s overall) would lower the water table by a maximum of 5.42 m, which would approximate its original level before the water table began to rise due to irrigation. The zone sensitive to this abstraction process would cover an area of approximately 14 km2. This technique could be improved by reducing inflows through the use of water-saving irrigation practices and/or applying corrective measures to increase groundwater outflows, which would eventually be demineralized.

Temporal Upscaling of Rice Evapotranspiration Based on Canopy Resistance in a Water-Saving Irrigated Rice Field

AbstractAn important element of the hydrologic cycle, the hydrometeorological parameter of evapotranspiration (ET), is critical in the development of effective water resources planning and irrigation scheduling. The ET varies in response to changes in resistance at the canopy surface rc and soil moisture content θ, especially under water-saving irrigation (WSI) practices. Drawing on data collected by eddy covariance in WSI rice paddies in eastern China in 2015 and 2016, variations in ET were studied by calculating and analyzing hourly canopy resistance and daily canopy resistance . Discrepancies were noted between true daily ET with respect to the estimated daily ET at different periods [0700–1600 local time (UTC + 8)]. To estimate in the WSI rice fields, the mean value between 0900 and 1000 LT, and between 1000 and 1100 LT performed considerably better than for a single time. Seasonal estimated ET can be accurately calculated by interpolating at different time intervals, thereby achieving a greater correlation and consistency at 2-day intervals. Then a generalized two-segment line of variation was used to calculate , achieving good results and showing that in the absence of observational data, could be easily calculated through a simplified pattern of variability. In conclusion, an ET temporal upscaling method for a WSI paddy, based on variation in and values, was optimized and is recommended for local application. Future work will focus on temporal upscaling of ET by extrapolating remote sensing instantaneous estimates to daily values.

Soil CO2 emissions from summer maize fields under deficit irrigation.

Irrigation practice is one of the main factors affecting soil carbon dioxide (CO2) emission from croplands and therefore on global warming. As a water-saving irrigation practice, the deficit irrigation has been widely used in summer maize fields and is expected to adapt to the shortage of water resources in Northwest China. In this study, we examined the impacts of deficit irrigation practices on soil CO2 emissions through a plot experiment with different irrigation regimes in a summer maize field in Northwest China. The irrigation regimes consisted of three irrigation treatments: deficit irrigation treatments (T1: reduce the irrigation amount by 20%, T2: reduce the irrigation amount by 40%) and full irrigation (T0) treatments. The results showed that the soil CO2 cumulative emissions with T1 and T2 were decreased by 9.8% (p < 0.05) and 14.3% (p < 0.05), respectively, compared with T0 treatment (1365.3 kg-C ha-1). However, there were no significant differences between T1 and T2 treatments (p > 0.05). Soil CO2 fluxes with different irrigation treatments showed significant correlations with soil moisture (p < 0.001) and soil temperature (p < 0.05). It was also observed that summer maize yields with T1 and T2 treatments were reduced by 4.9% (p > 0.05) and 30.9% (p < 0.05), compared with T0 (34.3 t ha-1), respectively. The findings demonstrate that the deficit irrigation treatment (T1) resulted in a considerable decrease in soil CO2 emissions without impacting the summer maize yields significantly. The results could be interpreted to develop better irrigation management practices aiming at reducing soil CO2 emissions, saving water, and ensuring crop yield in the summer maize fields in Northwest China.

Water-saving irrigation practices for rice yield information and nitrogen use efficiency under sub-tropical monsoon climate

Abstract Simple and practical water-saving irrigation practices (WIP) with nitrogen-reduction are beneficial to the development of rice cultivation technology with promotion of resource-conservation and environmental friendliness. The effects of WIP with nitrogen-reduction on population quality, annual yield and nitrogen use efficiency were studied by a field experiment. WIP could maintain or increase the annual yield of rice production models. The highest annual yield of more-water-saving irrigation practice (WIP150) was 8.42 t hm−2 for the double-season rice production model and 12.71 t hm−2 for the ratoon rice production model, respectively. Compared with non-application of nitrogen, the annual yield of nitrogen-reducing practice (NRP) and farms' fertilizer practice (FFP) increased significantly (p &amp;lt; 0.01), while a non-significant difference of annual yield between the FFP and NRP was observed; the annual yield of the NRP and FFP was 9.73 and 10.02 t hm−2 of the double-season rice production model, and 12.84 and 14.34 t hm−2 of the ratoon rice production model, respectively. AEN, PEN, PFPN and RUEN of the NRP were higher than those of the FFP. Therefore, observing the change of water layer in the soil layer via a simple self-made PVC indicator tube, reducing about 20% nitrogen quantity was a feasible and simple cultivation technique for water-saving and nitrogen-reduction in the rice production models.

Do alternative irrigation strategies for rice cultivation decrease water footprints at the cost of long-term soil health?

The availability of water is a growing concern for flooded rice production. As such, several water-saving irrigation practices have been developed to reduce water requirements. Alternate wetting and drying and mid-season drainage have been shown to potentially reduce water requirements while maintaining rice yields when compared to continuous flooding. With the removal of permanently anaerobic conditions during the growing season, water-saving irrigation can also reduce CO2 equivalent (CO2eq) emissions, helping reduce the impact of greenhouse gas (GHG) emissions. However, the long-term impact of water-saving irrigation on soil organic carbon (SOC)—used here as an indicator of soil health and fertility—has not been explored. We therefore conducted a meta-analysis to assess the effects of common water-saving irrigation practices (alternate wetting and drying and mid-season drainage) on (i) SOC, and (ii) GHG emissions. Despite an extensive literature search, only 12 studies were found containing data to constrain the soil C balance in both continuous flooding and water-saving irrigation plots, highlighting the still limited understanding of long-term impacts of water-saving irrigation on soil health and GHG emissions. Water-saving irrigation was found to reduce emissions of CH4 by 52.3% and increased those of CO2 by 44.8%. CO2eq emissions were thereby reduced by 18.6% but the soil-to-atmosphere carbon (C) flux increased by 25% when compared to continuous flooding. Water-saving irrigation was also found to have a negative effect on both SOC—reducing concentrations by 5.2%—and soil organic nitrogen—potentially depleting stocks by more than 100 kg N/ha per year. While negative effects of water-saving irrigation on rice yield may not be visible in short-term experiments, care should be taken when assessing the long-term sustainability of these irrigation practices because they can decrease soil fertility. Strategies need to be developed for assessing the more long-term effects of these irrigation practices by considering trade-offs between water savings and other ecosystem services.