Net Irrigation Requirement Research Articles

Adapting a Cloud-Based Irrigation Scheduler for Sugar Beets in the High Plains

Highlights An existing sugar beet crop coefficient curve (K cr ) was modified to better represent canopy development in northeast Colorado conditions. The modified K cr curve improved the estimated soil water deficits (net irrigation requirements) calculated by the cloud-based Water Irrigation Scheduler for Efficient Application (WISE App). Feedback from sugar beet growers and agronomists helped expand WISE applicability in the northern High Plains with access to additional weather station networks and functionality to aggregate irrigation data across multiple sugar beet fields or regions. Abstract . The convergence of agrometeorological network, database, and cloud-computing technologies has enabled greater accessibility of irrigation management tools for growers. The goal of this research and outreach project was to adapt an existing cloud-based irrigation scheduler (WISE) for use by sugar beet (Beta vulgaris L.) producers in eastern Colorado and a wider area of a cooperative operating in Colorado, Nebraska, Wyoming, and Montana. Four center pivot sugar beet fields in northeast Colorado were monitored during the 2013 and 2014 growing seasons. Soil water, leaf area index (LAI), and weather data were used to estimate the soil water deficit (net irrigation requirement) and to modify a crop coefficient (Kcr) curve originally reported in the literature based on growing degree days (GDD). The average cumulative GDDs for sugar beets to mature (100% maturity) was 2,944°C·d. The localized Kcr had a peak value (Kcr,mid) occurring between 43% and 69% of maturity, which corresponded to effective full cover (LAI = 3) and start of leaf senescence, respectively. In contrast, the original Kcr curve from literature had a longer duration of Kcr,mid spanning 33% to 83% of maturity. Use of the modified Kcr curve in lieu of the original Kcr curve in WISE reduced the relative error of soil water deficits by 12% to 35%. Feedback and collaborations from representative sugar beet growers and agronomists in the Western Sugar Cooperative led to expansion of WISE weather data access in the High Plains to include sugar beet growing areas in western Nebraska, eastern and northern Wyoming, and southern Montana. Keywords: Crop coefficient, Evapotranspiration, Irrigation scheduling, Soil water balance, Soil water deficit, Sugar beets.

Water requirement of rice crop using CROPWAT model for Dehradun district, Uttarakhand

Management of water resources with optimal utilization results in fulfilling the constraint of inadequate water availability. Determination of crop water requirement is the first step in planning and effective utilization of irrigation water which curtaining the impact developed due to water stress condition. In the present study crop water requirement (CWR) and irrigation requirement was computed for rice in Dehradun district using CROPWAT simulation software by taking into account different local climatic parameter which influencing reference crop evapotranspiration (ET0) and thus affecting crop production. Penman–Monteith method was used to calculate ET0 and the United States Department of Agriculture (USDA) soil conservation method was used to estimate the effective rainfall. The ET0 varied from 1.43 (January) to 5.28 (May) mm/day and annual mean was 3.1 mm/day. The average annual rainfall value was 1718 mm and out of which 977.3 mm was effective rainfall. The crop water requirement and net irrigation water requirement (NIR) for rice crop was estimated to be 559.5 mm and 288.7 mm, respectively. The values of CWR and NIR were maximum in June and minimum in October. The net scheme irrigation requirement was scheduled to be maximum in June (190.6 mm/month), minimum in October month and zero in the month of July, August and September. The actual irrigated area was found to be 18.92 km2 for which net irrigation demand was maximum in the month of June (3.61 MCM) followed by October month (0.12 MCM). Total net irrigation demand for actual irrigated area was 5.47 MCM. The computation of crop water requirement, NIR, and total net irrigation demand using CROPWAT has proved to be an effective tool for proper management of water resources in water stress condition.

Effect of the optimized regulated deficit irrigation methodology on water use in barley under semiarid conditions

In areas with low availability of irrigation water, it is necessary to improve water-use efficiency in crops, especially if their profitability is low. This is the case of barley in the Castilla-La Mancha region (Spain), where farmers are demanding methods to achieve adequate harvests with a supply of low amounts of irrigation water to this particular crop. The optimized regulated deficit irrigation (ORDI) methodology was developed to maximize the yield of annual crops under water-scarce conditions. The objective of this study was to determine the effect of ORDI for a limited amount of available irrigation water on yield, water productivity and water footprint of a barley crop (Shakira cv.) under semiarid conditions. To this end, five irrigation treatments were performed over three years (2015–2017) on an experimental farm located in Albacete province: no deficit (ND) (control), and four with different volumes of available irrigation water, corresponding to 100 % (T100), 90 % (T90), 80 % (T80), and 70 % (T70) of barley net irrigation requirements (2500 m3 ha-1) for the weather conditions of the intermediate typical meteorological year. As expected, yield decreased with deficit and ND was the treatment that achieved the highest average yield (9049 kg ha-1). While the average yield decreased by 19.4 % and 29.9 % with regard to ND, the highest average irrigation water productivity was for T80 and T70 (average 3.63 kg m-3), as these treatments reduced the average amount of irrigation water by 39.1 % and 46.7 %, respectively. Nevertheless, in terms of water-use sustainability, the most interesting treatment was T80, which achieved the lowest average water footprint (531 m3 Mg-1) while ND showed the highest (9.5 % greater). Consequently, ORDI yielded barley harvests with more efficient water use under limited volumes of available irrigation water and unknown climatic conditions, which were drier than typical in the three experimental years.

Impacts of climate change on irrigation water requirement of date palms under future salinity trend in coastal aquifer of Tunisian oasis

In coastal saline areas, many studies ignore salinity problems when quantifying the impacts of climate change on irrigation water requirement. Based on 11 years (2008–2018) of field investigations in a Tunisian coastal oasis, this study simulated the changes in salinity in a coastal aquifer and quantified changes in net irrigation requirement (NIR) of date palm under climate change, considering required changes in leaching requirement. The future salinity in the aquifer was simulated based on sea level rise and changes in aquifer recharge. The study applied a statistical downscaling model (SDSM) to project future climate variables from 2019 to 2050, the SUTRA model to evaluate the change in aquifer salinity, and applied CROPWAT software to calculate NIR. Three climate change scenarios were considered: RCP8.5 (very high emission scenario), RCP6.0 (medium emission scenario) and RCP4.5 (lowest emission scenario). Several useful finding were revealed in this study. First, these three climate change scenarios showed significant trend of increasing annual maximum and minimum temperatures, relative humidity, wind speed, and solar radiation, and a significant decreasing trend of future rainfall. Second, the average aquifer salinity is expected to increase from an average of 4.2 dS m−1 in 2018 to about 5.3 dS m−1 in 2050. Seawater intrusion was identified as the main cause for this remarkable increase. Finally, NIR is expected to increase from an average value of 1459 mm year−1 during 2008–2018 to 1473–1950 mm year-1 during 2019–2050, depending on climate change scenario applied. Increase in aquifer salinity significantly contributed to this rapid increase of NIR. We believe that our results should be considered in developing adaptation strategies to manage future water resources in coastal areas.

Estimation of water requirement of Banana crop under drip irrigation with and without plastic mulch using dual crop coefficient approach

Field experiments were conducted on the lateritic sandy loam soil and sub-humid climate of Kharagpur, West Bengal, India during 2014-2018 for two consecutive crop seasons to determine the optimum water requirement of the Banana crop under drip irrigation with and without plastic mulch. Reference evapotranspiration for the Banana crop was estimated using FAO-56 Penman-Monteith approach. The dual crop coefficient approach was used to improve the estimates of the crop coefficient (Kc) values for the irrigation treatments with black plastic mulch and without mulch. Plants treated with black plastic mulch consume about 12% less water for the main crop and about 22% less water for ratoon crop compared to non-mulch plants. The effect of black plastic mulch was studied to determine the soil moisture distribution in different soil depths (0-20, 20-40, 40-60, and 60-90 cm), and also loss of water through deep drainage. Net irrigation requirement under black plastic mulch was found to be lesser than without mulch. The deep percolation was found 50.4 % more under black plastic mulch in comparison to non-mulch treatment.

Analysis of climate change effects on crop water availability for paddy, wheat and berseem

Climate change has been a serious concern in the 21st century and mitigation strategies on its effects are less researched. The increase in temperature and changes in rainfall have forced researchers to ponder over reducing the wastage of fresh water. This paper deals with the rain water availability and the crop evapotranspiration (ETc) changes occurring and projected to occur over a time period of fifty years. Three major crops, paddy, wheat and berseem fodder were considered for three locations. Observed data and forecasted data for precipitation and temperature was obtained from India Meteorological Department and Can Esm2 model respectively. The Mann–Kendall (MK) test and the Thiel-Sen's Slope estimator (TSS) test were applied on the crop stage wise aggregated rain water available and the ETc to analyze the effects of climate change. In addition to the above study, the historical and projected means of crop period wise aggregated effective rainfall, total net irrigation requirement and total crop water requirement for a range of dates of sowing/transplanting for the above mentioned crops and locations were analyzed. It was seen by the analysis that the rainwater availability is seen to decrease and the temperatures increase with a delay in the sowing dates in the future scenarios causing an increase in the crop water requirements. Suitable shifting of the crop sowing or transplanting dates is seen to aid to better exploit the available rainwater and minimize the irrigation application.

GIS‐Based Surface Irrigation Potential Assessment for Ethiopian River Basin

AbstractThe suitability of the Dirma River Basin in Ethiopia for surface irrigation potential development and identification of potentially irrigable sites were the subject of the present study. The river basin area suitability was evaluated based on slope, soil and surface water resource availability using ArcGIS 10.1. Potentially suitable sites for surface irrigation development were evaluated for potato and tomato crops. The reference crop evapotranspiration, effective rainfall, net irrigation and gross irrigation water requirement were estimated using CROPWAT software. The results of the suitability model developed indicated that about 68.3% of the total river basin area falls in marginally to highly suitable categories for surface irrigation development. The water resource availability reveals that due to very high intra‐annual variability in river flows, only 6% of the mean annual flow is available for the period from January to May, and with this up to 30% of land that is suitable for surface irrigation can be irrigated. However, with suitable water storage infrastructure and deficit irrigation practices, utilization of land and water resources of the Dirma River Basin can be increased significantly. Therefore, this study will help decision makers, investors, planners and policymakers at the local, regional and national levels in better identification of profitable and sustainable irrigation investment opportunities in the region. © 2019 John Wiley & Sons, Ltd.

Irrigation Practices as Alternative Means of Supporting Rain-fed Agriculture: A Case Study of Potato (Solanum tuberosum L.)

Estimation of evapotranspiration is important for study, design, determining crop water requirement and management of irrigation systems. Also it’s important for determining irrigation water requirement during dry spell and water shortage i.e. when the evapotranspiration is greater than effective rainfall. Based on this, the study was conducted in Cheha district, Gurage Zone with determine crop water requirement of potato. In line to this, ten years climatological recorded data (2008-2017) for Indibir station on (sunshine duration hr /day), maximum and minimum temperature ( O C), humidity (%) and wind speed (km/day) at 2 meters height were used to determine ET o using Penman combination method. Secondary data were used to collect important soil parameters required for determination of crop water requirement. Lengths of growing periods, planting date and crop varieties data were received from the validation value of the local farmers and CDAO. Crop coefficients (kc), rooting depth, critical depletion fractions, yield response factors and crop height were obtained from food and agriculture organization of the United Nations guidelines (No. 56). The analyzed data indicated that reference crop evapotranspiration ranged from 2.40 to 4.73 mm with a mean of 3.56mm. The assessment has showed that the water requirement of potato is 63.2, 84.1, 145.8 and 77.2mm during initial, development, mid and late growth stages, respectively. The effective rainfall contribution throughout the growing stage of potato in the area is 8.5, 23, 187.2 and 158.1mm all through initial, development, mid and late growth stages, whereas the net irrigation requirement of potato throughout the dry spell period is 52.9, 61.3, 14.9 and 0mm in initial, development, mid and late growth stages, respectively. Soil and water conservation management practice, water harvesting technology and agronomic practices should be applied, principally mulching is very important to save soil moisture during high heat stress and dry spell or water shortage. Key terms: reference evapotranspiration, crop water requirement, potato DOI : 10.7176/JAAS/55-03 Publication date :May 31 st 2019

Application of Multi-Index Decision Analysis to Management Scenarios Considering Climate Change Prediction in the Zayandeh Rud River Basin

Considering the multidimensionality of water resources management policies and prioritization of water demands, engineering software have attracted researchers and planners. The Water Evaluation and Planning (WEAP) program (Multi-Attribute Decision Analysis Model) is one of the specialized software that uses the Water Algorithm Equation and is used for water resources planning and management at the watershed level. In order to forecast future water resources, runoff for the years to come by 2100 was first simulated using WEAP along a new climate prediction model (CMIP5) and a rainfall-runoff model. Then, the amount of drinking water and industry needs and net irrigation requirement were calculated by 2100. Results showed that by applying the climate prediction model and considering the effect of human factors on water resources and applying adaptive correction scenarios for the years to come, allocation of water resources in the Zayandeh Rud area was used to predict the status of water resources for planning. Considering the WEAP model for optimal water allocation, it can be admitted that agricultural demand can be met with 60% confidence and drinking water and the industry requirements can be met with 83% confidence.

Towards integrated water resources management considering hydro-climatological scenarios: an option for sustainable development

BackgroundIn the rainfed areas, water, not land, is the foremost restraining resources for better agricultural production to satisfy the growing demand of food and other needs. Water harvesting and enhancing productivity of available water, and not volume of yield per units of land, is therefore a better solution for rainfed agriculture. Under these circumstances, it is necessary toimplement efficient and effective integrated water resources management practices. Elsewhere rainfed dependent highland parts of Ethiopia, in the Beressa watershed most of the rainwater lost in the form of runoff particularly during excess rainfall; therefore, the benefit of rainwater during less rainy season is insignificant. The objective of this study therefore was to assess crop water requirement and net irrigation requirement using CROPWAT8.0 model and Rainfall Contribution Index (RCI) for various crops and to describe the benefits of water harvesting and integrated and sustainable water resources management. Crops growing during the month of February to June (less rainy season) are among the highest irrigation requirements.ResultsBased on RCI (as the value far from 1) reflect rainfall contribution is insufficient to satisfy the crop water requirements for the whole growth stages. Therefore, there is a need for supplemental irrigation and rainwater harvesting and a necessity for integrated water resources management. To reduce the intensity of water shortage therefore conservation planning and water management at watershed level in an integrated manner is critical. Similarly, soil and water conservation management practices is essential for the communities to reduce runoff and other resources for future uses and determine the optimal amount of water resources consumption at the irrigation fields is an urgent issues.ConclusionsAs a result, there is a need to do more efforts related to water harvesting and integrated water resources management for the sustainability of agriculture and over all human survival.

Water Requirements of Drip-Irrigated Maize (Zea mays L.) with Plastic Mulching in Heilongjiang, Northeast China

Abstract. A large area of rainfed maize ( L.) is planned to be replaced by maize under drip irrigation with plastic mulching (MDI) in Heilongjiang, northeast China, through a “water-saving and grain-increasing action” project. However, knowledge is lacking on the water requirements of maize under MDI. On the basis of a locally developed crop coefficient for a site, the spatial and temporal variations in crop water requirement (ETc) and net irrigation requirement (Nir) of maize under MDI in Heilongjiang were evaluated. The average ETc and Nir of maize under MDI in the period from 1960 to 2017 for 29 meteorological stations were 279 to 388 mm and 73 to 198 mm, respectively, which are approximately 10% and 15% lower than the ETc and Nir under conventional surface irrigation (NSI). The differences in ETc and Nir between the two irrigation technologies are significant in the southwestern region, which demonstrates that the intensive planning of MDI in the southwest is justified. The gross irrigation requirement of maize under MDI in an excessive drought year is estimated as 437 million m3 for the project, which is 137 million m3 less than the irrigation requirement using NSI.HighlightsAverage ETc and Nir of maize under MDI are approximately 10% and 15% lower than those under NSI.The differences in ETc and Nir are significant in the southwestern region of Heilongjiang.The estimated gross irrigation requirement of maize under MDI is much less than that under NSI. Keywords: Crop coefficient, Drip irrigation, Maize, Northeastern China, Plastic mulch, Water requirement.

Evaluation of the potentials of supplementary irrigation for improvement of sorghum yield in Wag-Himra, North Eastern, Amhara, Ethiopia

Water is the most limiting factor for agricultural production in dry land areas. supplying of adequate water is very crucial in stablizing crop yields and increasing their production. Therefore, the experiment was conducted for two cropping seasons (2014 to 2015) at Aybra on farmer’s plot in Sekota district of Wag-Himra Zone, Eastern Amhara. The objective of the experiment was to determine the net irrigation requirement and schedule of supplementary water application during moisture stress period and to improve crop water productivity of sorghum yield. The design of the experiment was random complete block design and seven treatments (C1, C2, FMSO, S1, S2, S3 and S4) with three replications were tested. The statistical analysis indicated that a significant difference in head weight, grain yield, stem diameter, and water productivity of sorghum among treatments. The analysis of variance for both years showed that there was a significant interaction effect between treatments across years on head weight, grain yield, and water productivity. Supplementing the crop with S3 and S1 treatments the application of 219.4mm and 328.4mm of irrigation water respectively at eight days interval at moisture stress time was obtained better head weight, grain yield, water productivity, and stem diameter. Therefore, this research recommended that supplementing rain-fed for sorghum production starting from the development stage (20 days after sowing down to harvesting). However, water is a limiting factor for crop production supplementing during development and mid-season stage only at eight days interval at moisture stress or rainfall is ceased.

Adjustment of Irrigation Schedules as a Strategy to Mitigate Climate Change Impacts on Agriculture in Cyprus

The study aimed at investigating eventual deviations from typical recommendations of irrigation water application to crops in Cyprus given the undeniable changes in recent weather conditions. It focused on the seasonal or monthly changes in crop evapotranspiration (ETc) and net irrigation requirements (NIR) of a number of permanent and annual crops over two consecutive overlapping periods (1976–2000 and 1990–2014). While the differences in the seasonal ETc and NIR estimates were not statistically significant between the studied periods, differences were identified via a month-by-month comparison. In March, the water demands of crops appeared to be significantly greater during the recent past in relation to 1976–2000, while for NIR, March showed statistically significant increases and September showed significant decreases. Consequently, the adjustment of irrigation schedules to climate change by farmers should not rely on annual trends as an eventual mismatch of monthly crop water needs with irrigation water supply might affect the critical growth stages of crops with a disproportionately greater negative impact on yields and quality. The clear increase in irrigation needs in March coincides with the most sensitive growth stage of irrigated potato crops in Cyprus. Therefore, the results may serve as a useful tool for current and future adaptation measures.

Spatial and Temporal Analysis of Precipitation and Effective Rainfall Using Gauge Observations, Satellite, and Gridded Climate Data for Agricultural Water Management in the Upper Colorado River Basin

Accurate spatial and temporal precipitation estimates are important for hydrological studies of irrigation depletion, net irrigation requirement, natural recharge, and hydrological water balances in defined areas. This analysis supports the verification of water savings (reduced depletion) from deficit irrigation of pastures in the Upper Colorado River Basin. The study area has diverse topography with scattered fields and few precipitation gauges that are not representative of the basin. Gridded precipitation products from TRMM-3B42, PRISM, Daymet, and gauge observations were evaluated on two case studies located in Colorado and Wyoming during the 2014–2016 irrigation seasons. First, the resolution at the farm level is discussed. Next, bias occurrence at different time scales (daily to monthly) is evaluated and addressed. Then, the coverage area of the gauge station, along with the impact of the dominant wind direction on the shape of the coverage area, is evaluated. Ultimately, available actual ET maps derived from the METRIC model are used to estimate spatial effective rainfall. The results show that the spatial resolutions of TRMM and PRISM are not adequate at the farm level, while Daymet is a better fit but lacks the adequate latency versus TRMM and PRISM. When compared against local weather station records, all three spatial datasets were found to have a bias that decreases at coarser temporal intervals. However, the performance of Daymet and PRISM at the monthly time step is acceptable, and they can be used for water resource management at the farm level. The adequacy of an existing gauge station for a given farm location depends on the willingness to accept the risk of the bias associated with a non-persistent, non-symmetric gauge coverage area that is highly correlated with the dominant wind direction. Among all goodness of fit statistics considered in the study, the interpretation of the summation of error makes more sense for quantifying the rainfall bias and risk for the user. Finally, based on the USDA-SCS model and actual spatial ET, overall, seasonal effective rainfall tends to be less than 60% of total rainfall for agricultural lands.

Characteristics and cause analysis of flue-cured tobacco's water requirements during growth periods in low latitude plateau area, China

Abstract This study aimed to identify the future changes in water requirements (ETc) of flue-cured tobacco by comparing estimated ETc values in the future with previous usage. This will provide a basis for estimating irrigation requirements, and help improve agricultural water use efficiency in the future. The Penman–Monteith equation and the single-crop efficient method were used to calculate the flue-cured tobacco ETc, net irrigation requirement (IR) and net irrigation requirement index (IDI) for the period 1956–2015, and the four Intergovernmental Panel on Climate Change (IPCC) AR5 emission scenarios were used to estimate ETc for two future periods (2046–2065 and 2081–2100) in the central Yunnan Province, China. The results showed that the IDI gradually decreased, along with the growth of flue-cured tobacco. The ETc, IR and IDI values increased with latitude in central Yunnan Province. Furthermore, the variations in the ETc over the whole growth period in the mid-21st century and late-21st century also tended to increase with latitude. In addition, based on the influence of climate variation on the ETc as assessed by a principal component analysis, precipitation was the main factor affecting flue-cured tobacco growth. This study contributes to the establishment of suitable irrigation systems for flue-cured tobacco at every growth stage in central Yunnan Province.

Water impacts of U.S. biofuels: Insights from an assessment combining economic and biophysical models.

Biofuels policies induce land use changes (LUC), including cropland expansion and crop switching, and this in turn alters water and soil management practices. Policies differ in the extent and type of land use changes they induce and therefore in their impact on water resources. We quantify and compare the spatially varying water impacts of biofuel crops stemming from LUC induced by two different biofuels policies by coupling a biophysical model with an economic model to simulate the economically viable mix of crops, land uses, and crop management choices under alternative policy scenarios. We assess the outputs of an economic model with a high-resolution crop-water model for major agricultural crops and potential cellulosic feedstocks in the US to analyze the impacts of three alternative policy scenarios on water balances: a counterfactual ‘no-biofuels policy’ (BAU) scenario, a volumetric mandate (Mandate) scenario, and a clean fuel-intensity standard (CFS) scenario incentivizing fuels based on their carbon intensities. While both biofuel policies incentivize more biofuels than in the counterfactual, they differ in the mix of corn ethanol and advanced biofuels from miscanthus and switchgrass (more corn ethanol in Mandate and more cellulosic biofuels in CFS). The two policies differ in their impact on irrigated acreage, irrigation demand, groundwater use and runoff. Net irrigation requirements increase 0.7% in Mandate and decrease 3.8% in CFS, but in both scenarios increases are concentrated in regions of Kansas and Nebraska that rely upon the Ogallala aquifer for irrigation water. Our study illustrates the importance of accounting for the overall LUC and shifts in agricultural production and management practices in response to policies when assessing the water impacts of biofuels.

Estimating net irrigation requirement of winter wheat using model- and satellite-based single and basal crop coefficients

Evapotranspiration (ET) is one of the key parameters in water and energy balance equation. According to FAO 56, crop evapotranspiration (ETc) is calculated from multiplying reference evapotranspiration (ET0) by crop coefficient (Kc). But, due to excessive simplification of Kc curve in the FAO approach, potential evapotranspiration (ETp) would be miscalculated. Therefore, accurate estimates of ETp entail improving Kc estimates. In this study, Kc curves of early- and late-planted winter wheat were obtained based on two main satellite-based methods: (1) ratio approach (2) vegetation indices (VIs) approach. In the ratio approach, basal crop coefficient (Kcb) and single crop coefficient (Kc) was directly calculated from the ratio of potential transpiration (Tp) to ET0 (using SWAP) and ETp to ET0 (using SWAP and the Priestly-Taylor equation), respectively. The VI approach makes use of Landsat 7 (ETM+) and 8 (OLI) and also MODIS imagery in order to extract soil adjusted vegetation index (SAVI). The Kcb curves were evaluated against field measured leaf area index (LAI) in 2014-15 growing season. After each Kc curve was modeled, net irrigation requirement (NIR) was calculated on daily and season basis. Results showed that the SWAP approach was weak in estimating the Kcb and Kc curves especially at the late-season stage. The VI approach could properly detect changes in vegetation cover during an entire growing season. But, when it came to Kc curve modelling, the VI approach was limited to the values given in FAO 56. However, the Priestly-Taylor approach compensated for this limitation therefore yielded more sensible trends in Kc curves. Results indicated that the VI approach reduced estimates of NIR of late-planted winter wheat compared with the FAO-recommended approach by 5.37%. The Priestly-Taylor approach resulted 21.72 and 0.32% lower NIR compared with the FAO-recommended approach respectively for early- and late-planted winter wheat. The decrease in NIR from satellite-based approaches derived from more realistic Kc curves during the entire growing season. Overall, making use of the satellite-based approaches could improve water management on regional scales.

Trends in water requirements of wheat crop under projected climates in India

Various global circulation models predict a change in net irrigation requirements worldwide due to the impacts of climate change and in India, depending upon the region, irrigation requirements are likely to change by different magnitudes. The spatial distribution of trend in crop and irrigation water requirements of wheat projected for two climatic periods (2021-50 and 2051-80) across major wheatgrowing districts of the country were analyzed, making use of climate change projection data from NorESM1-M model of the CMIP5 in combination with RCP 4.5. Decreasing trends in water requirements were projected over 90 per cent of wheat growing districts in 2021-50, whereas increasing trends in crop and irrigation water requirement are expected over 95.4 per cent and 62.4 per cent areas, respectively in 2051-80 climatic periods. Results showed that decreasing/increasing trends projected in water requirements of wheat crop is due to change in crop growing period, which is projected to decrease across entire wheat growing area in 2021-50, whereas it is likely to increase over 78.2 per cent in 2051-80 climatic periods.

The consequences of saline irrigation treatments on soil physicochemical characteristics

When saline water is used to irrigate crops in arid environments, appropriate irrigation management should be applied to avoid negatively impacting soil characteristics. In this study, the effects of irrigating date palms with saline water (2.24 g l−1) on soil physicochemical characteristics such as the electrical conductivity (ECe), the pH of the saturated soil paste (pHe), the concentrations of soluble cations (Ca2+, Mg2+, Na+), the sodium adsorption ratio (SAR), the saturated soil hydraulic conductivity (Ks), and the volumetric water content of the soil (θv) were evaluated in a Tunisian Saharan cropland, the Dergine Oasis, during a 4-year period (2012–2015). The effects of three different irrigation treatments of date palms on soil properties were investigated: low treatment (90% of the net irrigation requirement (NIR) of date palms was applied); medium treatment (100% of NIR was applied), and high treatment (110% of NIR was applied). The results showed that the application of saline water for irrigation inevitably has a negative impact on the physicochemical properties of the soil. Irrigation with saline water was observed to have severe negative impacts on the soil characteristics, especially ECe, Na+, Ks, and θv. However, among the three irrigation treatments applied, statistical analysis (Duncan’s multiple range test) indicated that the high treatment significantly (p < 0.05) minimized the degradation of soil characteristics by the saline water; this treatment decreased ECe, Na+, and SAR and increased the water content, θv, of the studied soil.

Estimating Net Irrigation Requirements of Winter Wheat across Central-Eastern China under Present and Future Climate Scenarios

AbstractClimate change (i.e., fluctuating precipitation and increasing temperature) is extremely likely to challenge water systems through an increased water demand, potentially impacting water use...