Agriculture In Semi-arid Regions Research Articles

Multiscale Assessment of Agricultural Consumptive Water Use in California's Central Valley.

Spatial estimates of crop evapotranspiration with high accuracy from the field to watershed scale have become increasingly important for water management, particularly over irrigated agriculture in semiarid regions. Here, we provide a comprehensive assessment on patterns of annual agricultural water use over California's Central Valley, using 30‐m daily evapotranspiration estimates based on Landsat satellite data. A semiempirical Priestley‐Taylor approach was locally optimized and cross‐validated with available field measurements for major crops including alfalfa, almond, citrus, corn, pasture, and rice. The evapotranspiration estimates explained >70% variance in daily measurements from independent sites with an RMSE of 0.88 mm day−1. When aggregated over the Valley, we estimated an average evapotranspiration of 820 ± 290 mm yr−1 in 2014. Agricultural water use varied significantly across and within crop types, with a coefficient of variation ranging from 8% for Rice (1,110 ± 85 mm yr−1) to 59% for Pistachio (592 ± 352 mm yr−1). Total water uses in 2016 increased by 9.6%, as compared to 2014, mostly because of land‐use conversion from fallow/idle land to cropland. Analysis across 134 Groundwater Sustainability Agencies (GSAs) further showed a large variation of agricultural evapotranspiration among and within GSAs, especially for tree crops, e.g., almond evapotranspiration ranging from 339 ± 80 mm yr−1 in Tracy to 1,240 ± 136 mm yr−1 in Tri‐County Water Authority. Continuous monitoring and assessment of the dynamics and spatial heterogeneity of agricultural evapotranspiration provide data‐driven guidance for more effective land use and water planning across scales.

Influence of tied-ridge-furrow with inorganic fertilizer on grain yield across semiarid regions of Asia and Africa: A meta-analysis

BackgroundIn semiarid areas, low productivity of crops has been attributed to lack of appropriate soil moisture conservation practices since droughts and soil erosion are rampant in most areas of this region. Consequently, ridge-furrow rainwater harvesting is widely used in these regions across the globe. Despite ridge-furrow being widely practiced, tied-ridge-furrow has not been extensively adopted by small-scale farmers in semi-arid regions. Consequently, the effectiveness of tied-ridge-furrow as a viable method of increasing crop yield has received less attention.MethodologyFor large-scale implementation, a detailed assessment of how ridge furrow, tied–ridge-furrow with fertilizer, tied-ridge-furrow with mulching and tied-ridge-furrow without mulching or fertilizer influence crop yield in different agro-environments under varying climatic conditions is needed. This study used the PRISMA guidelines to determine the impact of tied-ridge-furrow rainwater harvesting technique with mulching or fertilizer on sorghum (Sorghum bicolor) and pearl millet (Pennisetum glaucum) grain yields.ResultsSorghum grain yield increased by 17% greater in tied-ridge-furrow without mulching or fertilizer in comparison to flat planting. This may be due to increase in soil organic carbon in the region (9 g kg−1). Grain yield of millet significantly increased by 20–40% in Africa from 18 study observations in tied-ridge-furrow with fertilizer application as compared to tied-ridge-furrow without mulching or fertilizer treatments. This might be due to the significant increase in total nitrogen by 13–42% in the soil at <50 mg kg−1 quantity which had an effect size of 469.14 [65.60, 872.67]. In terms of soil texture, grain yield of millet and sorghum significantly increased in heavy textured soils (clay loam, silt clay, and clay soils) with an effect size of 469.14 [65.60, 872.67] compared to light and medium-textured soils of zero effect sizes. Millet and sorghum grain yields in tied-ridge-furrow with mulching, on the other hand, were not significantly different from those in flat planting. This may be due to the mulching materials used in those tests.ConclusionIn view of yields of sorghum and millet increased significantly by 32% and 17% in tied-ridge-furrow without mulching or fertilizer treatment compared to flat planting and tied-ridge-furrow with fertilizer treatment compared with tied-ridge-furrow without mulching or fertilizer treatment, respectively, this study recommend the use of fertilizers in a tied-ridge-furrow system to increase grain yield in semiarid areas compared to flat planting. Again, the study recommends more research on tied-ridge-furrow systems with other organic mulches and fertilizers in semiarid areas.

Multi-step cognitive mapping of perceived nexus relationships in the Seewinkel region in Austria

Multiple societal challenges such as climate change, water pollution and biodiversity loss require coordinated measures. Thereby the adoption of a nexus perspective is expedient. It acknowledges relationships between natural and social entities, and takes synergies and trade-offs of planned and implemented measures into account. We adopt a nexus perspective to elicit sectoral stakeholders’ perceptions on the relationships of the regional nexus entities, relevant measures and their perceived synergies and trade-offs in the semi-arid agricultural production region Seewinkel in East Austria. In a multi-step cognitive mapping approach, consisting of a workshop and semi-structured interviews, we developed an aggregated cognitive map with perceptions of stakeholders from agriculture, water management, nature conservation, tourism, the civil society, renewable energy and hunting. Workshop and interview transcripts were analyzed by means of a qualitative content analysis. Stakeholders agree on the priority of a good quantitative and chemical status of the regional groundwater body and a location-adapted agricultural production. They propose a combination of market-based, legal and technical measures supported by cross-sectoral institutions in responding to regional nexus challenges. Stakeholders perceive divergent synergies and trade-offs. Perceived synergies may provide opportunities, which have not yet been considered for planning of measures. Perceived trade-offs require further examination and cross-sectoral discussion to encourage the implementation of measures. The aggregated cognitive map may improve stakeholders’ understanding for nexus relationships and facilitate social learning through viewing the interlinked nexus from distance and different perspectives. This may facilitate cross-sectoral dialogue and enable collective decision making to tackle regional nexus challenges.

Complexities of drought adaptive behaviour: Linking theory to data on smallholder farmer adaptation decisions

Smallholder farmers in semi-arid regions continuously face drought risk, leading to recurring crop damage, income loss and food insecurity, and they are taking adaptive measures to cope with this risk. By comparing and combining empirical data and existing behavioural theories, we studied the complexity of smallholder farmers' adaptive behaviour in Kitui, Kenya. We conducted interviews with key informants, a survey of disaster managers and an extensive questionnaire and choice experiment among local smallholders, and found that mistrust in forecasting and a strong belief in God appeared to be barriers to adaptation, while farm groups and past adaptation decisions seemed to stimulate the intention to adopt new measures. Our results confirmed the importance of several components of existing bounded rational theories in that risk appraisal, social norm, self-efficacy and response cost and efficacy significantly influence adaptive behaviour under drought risk. However, none of the evaluate theories could fully explain the observed behaviour. We further demonstrated that tailored extension services, improved early warning systems, ex-ante cash aid and low interest credit schemes increase the intention to adapt. While a general aversion to the current situation was evident, there was great heterogeneity in the preferences for these policies. Findings of this the extensive data collection and analysis can be used to identify the most vulnerable groups and develop well-targeted adaptation policies, and for designing, calibrating and validating of utility functions to model heterogeneous adjustment decisions in dynamic drought risk models.

Forage tree legumes and sustainable upland farming in Timor Island – Indonesia

Upland farmers in semi-arid region of Timor Island have frequently facing low and uncertain food crops production and chronic forage shortage during long dry season limiting livestock (cattle) production. This study explores forage development, particularly Leucaena and the dynamics of upland farming management among farmer groups in West Timor – Indonesia. The study mostly use forage data of ACIAR and AIAT-ENT collaboration research on forage development, particularly Leucaena conducted in ENT. The data were mostly analysed descriptively. The study showed that adoption of forage legume innovation, particularly Leucaena by upland farmers have solved forage shortage problem during long dry season in semi-arid region of Timor Island, it allowed farmers to do cattle fattening/shortening fattening period and improving crops (maize) production. Drawing on information regarding traditional farming (mixed-cropping) practices for food crops production and traditional local agro-forestry (Mamar) for perennial crops production, the research suggested that incorporated forage tree legume of Leucaena into both traditional farming system can improve/sustain crops and cattle production as well as environment.

Temporal integration of remote‐sensing land cover maps to identify crop rotation patterns in a semiarid region of Argentina

AbstractCrop rotations are key agronomic tools to enhance farm productivity, preserve soil, and ensure provision of ecosystem services. Knowledge of the spatio‐temporal distribution of crops over regions is essential to characterize rotations at field scale and estimate their impacts on several outcomes. Our objectives were to: (a) determine the diversity of cropping systems practiced in a semiarid region of central Argentina during an 8‐yr period and (b) use the generated high‐resolution crop rotation map jointly with estimates of soil erosion to evaluate the potential linkage between cropping sequences and water erosion intensity. Temporally aggregated seasonal land‐cover maps were used to derive spatially explicit crop rotations during 2011–2018 across a 6,000 km2 semiarid agricultural region in Argentina. Soybean (Sy) [Glycine max (L.) Merr.] and maize (Mz) (Zea mays L.) defined the major crop rotations of the study area. Sorghum [Sorghum bicolor (L.) Moench] and peanut (Arachis hypogaea L.) occupied minor areas and thus were assimilated into the dominant summer cropping systems. Only seven sequences of summer crops, most of them including soybean and maize, accounted for &gt;90% of the spatio‐temporal variability. Soybean monoculture was the dominant cropping system (28.5%), followed by a 3‐yr Sy–Sy–Mz rotation (23.9%), and other soybean‐dominated rotation patterns. In winter, the prevailing land cover was stubble (96.6%). The generated high‐resolution maps illustrate the low diversity of crops in the study area. Mapping the spatio‐temporal distribution of land cover allowed for quantification of land transformations and the examination of linkages between soybean monocropping and erosion.

Multi-criteria Land Suitability Analysis for Agriculture in Semi-Arid Region of Kadapa District, Southern India: Geospatial Approaches

This research proposes an integrated methodology for incorporating RS, GIS and AHP techniques for the assessment of agricultural land suitability. In Kadapa district, Andhra Pradesh, India, study is being done on how to best promote agriculture as a source of income to boost the economy of the region. A combined RS, GIS and AHP techniques has been utilized that incorporates organizing AHP hierarchy, criteria specification, pairwise comparison, and criterion map preparation. Land suitability comparison showed that an area of 4.42 km2 (2.62%) is appropriate for irrigation, while an area of 54.39 km2 (32.33%) is appropriate moderately suitable for rainfed agriculture and 95.76 km2 (56.93%) is marginally suitable for agricultural productions. About 13.64 km2 (8.11%) land is currently not suitable for agricultural production. Additionally, the analysis clearly shows the necessity of a decrease in irrigated agricultural land and an increase in dry farm agricultural land. This application of RS, GIS and AHP based agricultural land suitability analysis is helpful in referring agricultural activities to the areas with good physical and environmental conditions, allowing maximum agricultural efficiency in the countryside, increasing non-agricultural uses in areas with low efficiency, and avoiding the construction and environmental pressures on suitable farmland.

Isabgol (Plantago ovata) and lentil (Lens culinaris) intercrop responses to arbuscular mycorrhizal fungi inoculation

ABSTRACT Intercropping medicinal plants with grain legumes provides an excellent opportunity for small-scale farmers to generate more income and move towards sustainable cropping systems. The effect of arbuscular mycorrhizal fungi (AMF) inoculation on yield, quality and nutrient uptake of isabgol and lentil, when grown as monocrops or in various intercropping ratios, were evaluated. Inoculation with AMF resulted in positive effects on AMF root colonisation, yield components and seed yields (significant for lentils only) of both crops, especially in the intercropping systems, as well as in the nutrient uptake in isabgol. The highest seed yields of isabgol (743 kg ha−1) and lentil (684 kg ha−1) were obtained when these species were grown as monocrops and inoculated with AMF. The highest mucilage content (20.9%) and swelling factor (16.9 ml) of the isabgol seeds were found when the two secies were grown in the intercropping ratio of 2I:2L (2 rows isabgol: 2 rows lentil) and treated with AMF. Regarding the composition of the isabgol seed mucilage, the highest concentrations of galacturonic acid (9.0%), galactose (11.8%), glucuronic acid (18.3%), and xylose (39.0%) were recorded in intercropping with AMF treatment. AMF inoculation also increased soil basic microbial respiration, soil substrate-induced respiration and soil microbial biomass carbon. Overall, the highest land equivalent ratio (LER = 1.67) was recorded in the 4I:2L intercropping pattern with AMF inoculation. The results indicated that intercropping of isabgol and lentil together with AMF inoculation was an effective system to increase the use efficiency of resources for smallholder farmers in semi-arid regions.

Computing stochastic Pareto frontiers between economic and environmental goals for a semi-arid agricultural production region in Austria

Multi-objective programming is frequently used in agro-environmental management studies to find compromises between competing policy objectives. We develop an integrated modelling framework to compute stochastic Pareto frontiers using realizations of three climate scenarios (SIMILAR, DRY, WET) for the semi-arid Seewinkel region in Austria. The stochastic Pareto frontiers relate net benefits of agricultural production (NB) to three environmental goal indicators including groundwater extraction (GWEX), nitrate leaching (NO3), and topsoil organic carbon stocks (SOC). The simulation results depict trade-offs and environmental co-benefits depending on the climate scenario and induced land use changes. A 1% (or 20%) decline of NB reduces GWEX by 11–83% (or 61–100%) and NO3 by 18–19% (or 49–53%), and increases SOC by 1% (or 5%), depending on the climate scenario. The results also reveal some environmental co-benefits for all Pareto frontier combinations. Climate change intensifies or alleviates trade-offs between NB and environmental goal indicators: in a dry climate scenario, trade-offs between NB and GWEX as well as SOC increase, while in a wet climate scenario, trade-offs between NB and NO3 increase. Overall, we find that efficient climate change adaptation of land use and management practices significantly improves the environmental outcomes for fairly small reductions in agricultural net benefits.

Soil biological response to multi-species cover crops in the Northern Great Plains

Farmers in semi-arid regions are experimenting with cover crop mixtures as partial summer fallow replacement, with the goal of increasing soil biological activity. We compared extracellular enzyme activity, microbial biomass, potentially mineralizable nitrogen (PMN) and mycorrhizal colonization levels after growing cover crops comprised of one or four functional groups. We asked whether cover crops can alter those soil processes and components relative to fallow during the cash crop growing season, and whether a cover crop mixture (CCM) will have a greater impact than a single-species legume green manure (LGM) after one and two rotations with wheat. Cover crops were planted at two sites in Montana April 2012 and May 2014, and at two additional sites in May 2013, and April 2015, terminated at each site approximately 60 days after seeding. Wheat was the cash crop for the following growing season. Cover crop treatments included a fallow control, a sole pea LGM, and a FULL mix consisting of eight species, with two species of each of four functional groups. Four additional treatments of single functional groups were compared following the second rotation of cover crops. The geometric mean of soil enzyme activity increased after cover crops relative to fallow (1.1–1.3 fold) at two sites after the first rotation, and by 1.1–1.4 fold after the second rotation at three sites. At the fourth site, the geometric mean of the FULL mix was greater than LGM or fallow by 1.4 and 1.5 fold. The response of individual enzymes was less consistent. Microbial biomass and PMN increased after LGM and/or FULL at three of eight site-years, by 1.2–1.7 for microbial biomass and 1.6–2.1 for PMN. Mycorrhizal colonization of wheat increased in at least one cover crop treatment relative to fallow at four of six site-years, and decreased in cover crops relative to fallow at one site. There were no differences in soil biological traits measured among single-functional-group treatments. Soil biological parameters were correlated with cover crop biomass in 7 of 16 comparisons at two sites after one rotation. After two rotations, 5 of 8 soil parameters were correlated with cover crop biomass at one site, with no correlations for the remaining sites. Precipitation declined 30–50 % from the first rotations at those three sites. Positive effects of cover crops on soil biological parameters in semi-arid systems may be measurable only when environmental conditions do not limit growth.

Assessing social dimension of water security in villages of Harsin county in the semi-arid agricultural region of Kermanshah in west of Iran

Population growth and low average rainfall are main causes of drought and water-based problems in Iran. The present study assesses the level of resilience and coping capacity against water-based disasters, especially droughts on four villages of Harsin county in the semi-arid agricultural region of Kermanshah in west of Iran. The assessment of social dimensions of water security is considered as a quantitative research in terms of nature and functional in terms of objective. The statistical population of the study consisted of 6068 rural farmers and, using Krejcie and Morgan table, sample size was determined as 361 people, who were chosen via a stratified random sampling method. Data were gathered using a structured questionnaire whose face validity was confirmed through a panel of experts and its reliability was estimated using Cronbach’s alpha coefficient (above 0. 84). In this study, the paired comparisons using experts’ views to weigh indicators were used. According to the results of this section, infrastructural resilience and drought coping capacity have the highest importance in the concept of social dimension of water security. The study provides recommendations for policy and decision makers to enhance coping strategies at the local level to deal with water-based disasters in the study area.

Spatially and temporally assessing event-based wind erosion in adjacent plots of fallow and wheat cultivation in the Central Anatolia, Turkey

ABSTRACT Wind erosion is most likely influenced by unsuitable tillage and is considered critically harmful process for sustainable agriculture in arid and semi-arid regions as drought becomes more frequent and severe due to changes in the climate. The study was conducted for spatial modelling of aeolian sediment transport over adjacent plots managed by wheat-fallow rotation system under rainfed agriculture in the semi-arid region of Turkey. Four erosion events took place and the results were evaluated using data of 8 measurements over two plots during events. Wind-driven sediment transport rates (Qt) varied between 0.0015 and 0.0075 kg m−1 h−1, highly depending upon the prevalent land surface characteristics during each case, and there was no event-based conclusion that the semi-arid dryland fallow system would exacerbate wind erosion losses when Qt values from either plot were compared. Of all cases, particularly, the greatest soil loss occurred in Case 3 over the fallow plot, for which Qt values were 0.0075 kg m−1 h−1 when wheat crop provided full soil cover above the next plot. Geostatistical analyses revealed the range values as between 450 and 800 m. Kriging maps showed that spatial patterns of Qt values of cases for both land uses were almost quite different.

Informing groundwater policies in semi-arid agricultural production regions under stochastic climate scenario impacts

Region-specific groundwater policies are required to regulate groundwater extraction for agricultural irrigation and reduce climate change adaption externalities. We examine the semi-arid Seewinkel region in Austria and explore interactions between climatic, agronomic, hydrological, and socio-economic conditions and processes to provide policy advice. The assessment is conducted with a spatially explicit integrated modeling framework to analyze impacts on land and irrigation water use, land management, and net benefits of agricultural production. The model results show that with imposed groundwater restrictions for irrigation, land use shifts from irrigated vineyards to mostly rainfed cropland with declining regional net benefits of agricultural production. The direction of change is similar for a DRY, SIMILAR, and WET climate scenario, while the magnitude differs. We estimate that an increase of the marginal value of groundwater extraction for irrigation by 0.1 €/m3 results in an average decrease in groundwater extraction volumes by 17.2 Mm3 in DRY, 6.3 Mm3 in SIMILAR, and 6.4 Mm3 in WET. Furthermore, regional net benefits of agricultural production decrease by 3.4 M€ in DRY and SIMILAR, and by 1.6 M€ in WET, on average. Our assessment highlights that efficient groundwater policies can help to sustain groundwater availability in semi-arid regions, particularly under climate change.

Interplay of changing irrigation technologies and water reuse: example from the upper Snake River basin, Idaho, USA

Abstract. Careful allotment of water resources for irrigation is critical for ensuring the resiliency of agriculture in semiarid regions, and modernizing irrigation technology to minimize inefficient water losses is an important tool for farmers and agricultural economies. While modernizing irrigation technology can achieve reductions in the nonbeneficial use of water, such as bare soil evaporation and nonconsumptive losses, water returned to the landscape is also reduced, often eliminating flow paths that other users rely on. In basins using a combination of surface and groundwater, replenishing aquifer storage by the managed aquifer recharge (MAR) of seasonally available water can mitigate the aquifer drawdown that results from reduced recharge when irrigation efficiency is improved. We examine the effects of MAR on the system-scale efficiency of modernizing irrigation technology and the resulting changes in the reuse of nonconsumptive losses, using a macroscale hydrologic model applied to the semiarid upper Snake River basin (USRB) of western Wyoming and southern Idaho, USA. Irrigation technologies were represented explicitly in the model, and available data informed baseline parameterizations of the irrigation technology. A suite of parameterizations were simulated that updated the existing technologies to be more efficient, both with and without sufficient MAR to cause a stabilization of the aquifer at the present-day head. As expected, simulated changes in irrigation technology resulted in greater downstream export of pristine water and a higher rate of aquifer drawdown when MAR was not simulated. Under current water use and cropping patterns, we were not able to simulate aquifer stabilization and maintain discharge downstream at any level of irrigation efficiency. We found support for the hypothesis that, as efficiency improves, less MAR is required to maintain a stable aquifer than when return flows are reduced due to increased efficiency. To evaluate the hypothesis, we defined the management benefit as a metric that compared the difference between the change in irrigation's net recharge and the change in MAR required as irrigation technology became more efficient. The metric generally indicated that less MAR was needed than net recharge was lost, but only for the most efficient case did the management benefit exceed the MAR needed at the baseline to stabilize the aquifer. Increasing efficiency of irrigation technology reduced the reuse of the gross irrigation derived from prior nonconsumptive losses, but simulating MAR increased reuse for a given parameterization, leading to higher effective irrigation efficiency. We find that local groundwater storage that users depend on is generally more sensitive to management decisions than downstream flows, and the drawdown of the aquifer without MAR always exceeded any decrease in discharge induced by MAR. Improving resource sufficiency in semiarid systems like the USRB will require an array of solutions that will need to balance benefits to local and downstream users.

Gender and climate change linkages in the semi-arid region of Ghana

Climate change is projected to have a serious impact on all sectors of the world. The agriculture sector is one of the most vulnerable sectors with implications for smallholder farmers in semi-arid regions of Africa in terms of poverty and food security. Several researches have been carried out on perception and adaptation with a little investigation to unpack the gender differences and how this influence adaptation strategies. This research investigates gender difference and gender-specific adaptation strategies to climate change and variability. A household survey was conducted from August to December 2014 using a pre-tested questionnaire where 150 males and 150 female farmers were randomly sampled from 14 communities within the Bolgatanga Municipality and Bongo district. Results show the existence of gender differences in the adaptation strategies. Both gender groups perceived climatic change and variability but only 49% male and 40% female headed household (HH) have adopted strategies to cope with increasing temperatures while 56% male and 49% female have adapted to decreasing precipitation. On the other hand, 62% male and 60% female HH have adapted to increasing drought spells. The main differences between male and female adaptation strategies are that males prefer to migrate and seek employment in other parts of the country whereas females prefer to engage in off-farm jobs such as trading, basketry and shea-butter processing. The age of farmers, access to extension services, credit, perceived loss of soil fertility, among other factors influenced farmers adaptation strategies. Policy decisions to promote adaptation to climate change and variability should take these factors into consideration.

Recharge Estimation Using CMB and Environmental Isotopes in the Verlorenvlei Estuarine System, South Africa and Implications for Groundwater Sustainability in a Semi-Arid Agricultural Region

Groundwater recharge remains one of the most difficult hydrogeological variables to measure accurately, especially for semi-arid environments where the recharge flux is much smaller than in humid conditions. In this study, groundwater recharge was estimated using chloride mass balance (CMB) in the Verlorenvlei catchment, South Africa where the effects of recent severe drought conditions in an already semi-arid environment have impacted both agricultural activity as well as the RAMSAR-listed Verlorenvlei estuarine system. Chloride, 18O and 2H tracers were used to improve understanding of the groundwater flow patterns and allowed the fresh parts of the groundwater system, defined by Ca2+-HCO3− groundwater types, to be separated from those where additional salts were being introduced through groundwater mixing, and thus characterized as Na+-Cl− groundwater types. Recharge rates calculated from CMB in the fresh parts of the system were between 4.2–5.6% and 11.4–15.1% of mean annual precipitation for the headwater valley and mountains of the Krom Antonies and are largely consistent with previous studies. However, much lower recharge rates in the valleys where agriculture is dominant contrasts with previous results, which were higher, since groundwater-mixing zones were not recognised. Although the chloride concentration in precipitation is based on only one year of data between 2015 and 2016, where 2015 had on average 28% less precipitation than 2016, the results provide a snapshot of how the system will respond to increasing drought frequency in the future. The results suggest that low rates of groundwater recharge under dry spell conditions will impact on low flow generations which are required to sustain the Verlorenvlei estuarine lake system. Overall, the study highlights the importance of combining hydrochemical tracers such as bulk chloride and stable isotopes with numerical modelling in data-scarce catchments to fully understand the nature of hydrological resilience.

Plastic Film Mulching Sustains High Maize (Zea mays L.) Grain Yield and Maintains Soil Water Balance in Semiarid Environment

Ridge–furrow cultivation with plastic film mulching has been widely used for many years to increase crop yields in semiarid regions. The long-term effects of plastic mulching on crop yield and soil water balance need to be seriously considered to assess the sustainability of this widely used field management technique. A seven-year maize field experiment was conducted during 2012–2018 to estimate the yield sustainability and soil water balance with two treatments—mulching (yes; no) and nitrogen fertilization (yes; no). This resulted in the following four groups—no film mulching, no N application (M0N0); film mulching, no N application (M1N0); no film mulching, N application (M0N1); film mulching and N application (M1N1). Our results show that plastic mulching significantly increased maize yield. A combination of mulching and nitrogen application had the highest sustainability yield index (SYI) of 0.75, which was higher than the other three treatments, with SYI values of 0.31, 0.33, and 0.39, respectively. Plastic film mulching increased soil water content and water storage in both the sowing and harvesting periods and did not cause the formation of dry soil layers. Precipitation storage efficiency (PSE) in the nongrowing season played a key role in maintaining the soil water balance and it was positively affected by plastic film mulching. Our research indicates that plastic mulching and N application could maintain maize yield sustainability and the soil water balance of agriculture in semiarid regions. In addition, we highlight the importance of nongrowing season precipitation, and thus, we suggest that mulching the field land with plastic film throughout the whole year should be adopted by farmers to store more precipitation, which is important to crop growth.

Influence of Agricultural Irrigation Activity on the Potential Risk of Groundwater Pollution: A Study with Drastic Method in a Semi-Arid Agricultural Region of China

Agricultural irrigation strongly affects groundwater pollution in cultivated areas. Groundwater vulnerability was evaluated using the DRASTIC method by considering agricultural activities that affect water infiltration and pollutant transport to the groundwater. Three scenarios, using different water recharge sources and calculation methods, were considered for the Tongliao area of northern China. For Scenario 1, only precipitation contributed to the net recharge estimation and ~33.77% of the area was under high pollution risk. For Scenarios 2 and 3, both precipitation and irrigation return water were considered for net recharge estimations. The fractional areas of high pollution risk regions were 40.60% and 19.22% for Scenarios 2 and 3, respectively. The modified infiltration coefficients for this study area were used in Scenario 3, and the fractional area of the high-risk region was 21.38% lower than for Scenario 2. The use of empirical infiltration coefficients in Scenario 2 overestimated the water infiltration ability in the cultivated areas, which also overestimated the fractional area of high-risk regions in this study. Accurate assessment of the impact of agricultural activities on the groundwater pollution risk is essential for cultivated areas. Emphasis should be placed on the calculation method of proper parameters for DRASTIC model construction.

Optimizing Dryland Crop Management to Regional Climate via Simulation. Part I: U.S. Southern High Plains Cotton Production

Over semi-arid agricultural regions such as the U.S. Southern High Plains (SHP) producers of dryland crops need to know which management practices increase yields and decrease production risk. Here, a modelling approach is used to explore management options (MO) that increase dryland cotton yields and estimate those practice’s yield risk effects under current SHP climate conditions. To simulate current dryland yield variability, dense distributions of lint yield outcomes were generated using the CROPGRO-Cotton crop model driven by weather inputs from 21 SHP weather stations during 2005-2016. Management effects were explored by repeating simulations over 32 MOs defined by 4 planting dates, 4 planting densities, and applying or not applying nitrogen. Both earlier planting date and decreased plant density increased median simulated yields, with earlier planting having the greatest positive yield effects. The MO that produced the highest median lint yields planted on the earliest planting date (May 15), at the lowest density (3 plants m-1), and applied no nitrogen. Recent SHP field studies generally confirm the earlier planting date effect, but suggest insignificant yield effects for different seeding rates. Even so, negligible yield effects and lower input costs favor lower seeding densities from a profit standpoint. These crop simulations demonstrate a modelling-based method for climate-related agricultural risk management, and suggest mid-May planting dates and low plant densities as part of management practices that increase yields and profits in dryland SHP cotton production.

New perspective about application of extended Budyko formula in arid irrigation district with shallow groundwater

Budyko’s treatment of the long-term water balance of watersheds was based on the competition between water availability and energy supply. It assumes, in the long-term, that precipitation is the only source of water availability for evapotranspiration while the changes in soil water storage are negligible. For arid irrigation areas with shallow water tables, however, groundwater also can supply crop water demand in addition to irrigation and precipitation. In this study, we present a new Budyko formula considering seasonal groundwater uptake and soil water storage changes estimated by Aver’yanov’s equation and abcd model, respectively. The use of groundwater depths rather than the variation of groundwater levels makes it more reasonable to estimate seasonal groundwater consumption. For the application of the Budyko equation in unsteady state areas, equivalent precipitation was designed to take the place of precipitation as water availability. With the newly defined water availability, the relationship between evapotranspiration ratio and aridity index was described successfully by Budyko curves, otherwise the points exceeded Budyko domain with only precipitation and irrigation considered. Furthermore, for agricultural irrigation areas, the variation of seasonal ω is supposed to be affected by vegetation coverage (denoted by NDVI). Overall, it is possible to estimate regional actual seasonal and annual evapotranspiration for irrigation areas with shallow groundwater using the extended Budyko models. This new method can play significant role in water management in arid and semiarid agricultural regions.