Estimation of irrigation requirements for drip-irrigated maize in a sub-humid climate

Drip-irrigation is increasingly applied in maize （Zea mays L.） production in sub-humid region. It is cdtical to quantify irrigation requirements during different growth stages under diverse climatic conditions. In this study, the Hybrid-Maize model was calibrated and applied in a sub-humid Heilongjiang Province in Northeast China to estimate irrigation requirements for drip- irrigated maize during different crop physiological development stages and under diverse agro-climatic conditions. Using dimensionless scales, the whole growing season of maize was divided into diverse development stages from planting to maturity. Drip-irrigation dates and irrigation amounts in each irrigation event were simulated and summarized in 30-year simulation from 1981 to 2010. The maize harvest area of Heilongjiang Province was divided into 10 agro-climatic zones based on growing degree days, arid index, and temperature seasonality. The simulated results indicated that seasonal irrigation requirements and water stress during different growth stages were highly related to initial soil water content and distribution of seasonal precipitation. In the experimental site, the average irrigation amounts and times ranged from 48 to 150 mm with initial soil water content decreasing from 100 to 20% of the maximum soil available water. Additionally, the earliest drip-irrigation event might occur during 3- to 8-leaf stage. The water stress could occur at any growth stages of maize, even in wet years with abundant total seasonal rainfall but poor distribution. And over 50% of grain yield loss could be caused by extended water stress during the kernel setting window and grain filling period. It is estimated that more than 94% of the maize harvested area in Heilongjiang Province needs to be irrigated although the yield increase varied （0 to 109%） in diverse agro-climatic zones. Consequently, at least 14% of more maize production could be achieved through drip-irrigation systems in Heilongjiang Province compared to rainfed conditions.

Implications of future climate change on crop and irrigation water requirements in a semi-arid river basin using CMIP6 GCMs

Agriculture faces risks due to increasing stress from climate change,particularly in semi-arid regions.Lack of understanding of crop water requirement(CWR)and irrigation water requirement(IWR)in a changing climate may result in crop failure and socioeconomic problems that can become detrimental to agriculture-based economies in emerging nations worldwide.Previous research in CWR and IWR has largely focused on large river basins and scenarios from the Coupled Model Intercomparison Project Phase 3(CMIP3)and Coupled Model Intercomparison Project Phase 5(CMIP5)to account for the impacts of climate change on crops.Smaller basins,however,are more susceptible to regional climate change,with more significant impacts on crops.This study estimates CWRs and IWRs for five crops(sugarcane,wheat,cotton,sorghum,and soybean)in the Pravara River Basin(area of 6537 km^(2))of India using outputs from the most recent Coupled Model Intercomparison Project Phase 6(CMIP6)General Circulation Models(GCMs)under Shared Socio-economic Pathway(SSP)245 and SSP585 scenarios.An increase in mean annual rainfall is projected under both scenarios in the 2050s and 2080s using ten selected CMIP6 GCMs.CWRs for all crops may decline in almost all of the CMIP6 GCMs in the 2050s and 2080s(with the exceptions of ACCESS-CM-2 and ACCESS-ESM-1.5)under SSP245 and SSP585 scenarios.The availability of increasing soil moisture in the root zone due to increasing rainfall and a decrease in the projected maximum temperature may be responsible for this decline in CWR.Similarly,except for soybean and cotton,the projected IWRs for all other three crops under SSP245 and SSP585 scenarios show a decrease or a small increase in the 2050s and 2080s in most CMIP6 GCMs.These findings are important for agricultural researchers and water resource managers to implement long-term crop planning techniques and to reduce the negative impacts of climate change and associated rainfall variability to avert crop failure and agricultural losses.

Investigation of crop evapotranspiration and irrigation water requirement in the lower Amu Darya River Basin, Central Asia

High water consumption and inefficient irrigation management in the agriculture sector of the middle and lower reaches of the Amu Darya River Basin(ADRB)have significantly influenced the gradual shrinking of the Aral Sea and its ecosystem.In this study,we investigated the crop water consumption in the growing seasons and the irrigation water requirement for different crop types in the lower ADRB during 2004–2017.We applied the FAO Penman–Monteith method to estimate reference evapotranspiration(ET0)based on daily climatic data collected from four meteorological stations.Crop evapotranspiration(ETc)of specific crop types was calculated by the crop coefficient.Then,we analyzed the net irrigation requirement(NIR)based on the effective precipitation with crop water requirements.The results indicated that the lowest monthly ET0 values in the lower ADRB were found in December(18.2 mm)and January(16.0 mm),and the highest monthly ET0 values were found in June and July,with similar values of 211.6 mm.The annual ETc reached to 887.2,1002.1,and 492.0 mm for cotton,rice,and wheat,respectively.The average regional NIR ranged from 514.9 to 715.0 mm in the 10 Irrigation System Management Organizations(UISs)in the study area,while the total required irrigation volume for the whole region ranged from 4.2×109 to 11.6×109 m3 during 2004–2017.The percentages of NIR in SIW(surface irrigation water)ranged from 46.4%to 65.2%during the study period,with the exceptions of the drought years of 2008 and 2011,in which there was a significantly less runoff in the Amu Darya River.This study provides an overview for local water authorities to achieve optimal regional water allocation in the study area.

Determination of Reference Evapotranspiration Using Penman-Monteith Method in Case of Missing Wind Speed Data under Subhumid Climatic Condition in Hungary

The reference evapotranspiration was calculated using Penman-Monteith method proposed. This method was evaluated on data measured by lysimeter in Szarvas experimental station in Hungary. The results of the two methods were in good agreement. However, this method requires an amount of data which is not available at all sites of meteorological measurement. Therefore it was necessary to investigate which elements influencing evapotranspiration are important and which elements are less important. With the help of investigation was indicated that radiation and vapor pressure deficit play important role in determination of reference evapotranspiration. Taking into account this there was two possibilities to calculate evapotranspiration. One of these is to use Penman-Monteith formula with constant wind speed as advised by Allen. Another one is to neglect wind speed data. Both methods were investigated and the method with constant wind speed was found better in a subhumid climatic condition of Hungary.

Determination of Young Olive-Tree Water Consumption with Drainage Lysimeters

Information about olive-tree irrigation in sub-humid climates, as in Uruguay, is scarce. Water consumption of young olive trees, Arbequina variety, was measured for two years with six drainage lysimeters, protected from rain by an automatic rain-out shelter. Irrigation water volume and drainage of each lysimeter were measured daily and soil moisture was registered twice a week with neutron probe at four depths. Evapotranspiration (ETc) was calculated by volume balance. Data periods when available water descended below 50% or increased over 100% were eliminated, as those in which the stem water potential was below -1.5 MPa. Water consumption values were averaged within 7- to 14-day periods, expressed in mm·d-1, and referred to a 2.5 × 5.5 m plantation framework without vegetation cover. There was a positive linear relation of the summer crop coefficient (Kc mid) with age, canopy cover percentage and canopy volume. Canopy cover percentage was the parameter which explained most of the variation of Kc mid, which ranged between 0.13 and 0.24, with 5% and 46% canopy cover, respectively. Full irrigation, associated to a good drainage resulted in a rapid growth of the young plants, bringing forward the start of full production period. This represents useful information for the adjustment of irrigation in olive-tree orchards, to accelerate growth with a rational and sustainable use of both water and energy in Uruguay.

Irrigation water requirements of rice using Cropwat model in Northern Benin

Understanding crop water requirements(CWR)in semi-arid region is essential for better irrigation practices,scheduling and efficient use of water since the water supply through rainfall is limited.This paper estimated the crop reference and actual evapotranspiration(Eto and ETc)respectively and the irrigation water requirement of rice(Oryza sativa L.)in Benin’s sub-basin of Niger River(BSBNR)of west Africa,using CROPWAT model.The long recorded climatic data,crop and soil data from 1942 to 2012 were computed with the Cropwat model which is based on the United Nations’Food and Agriculture Organization(FAO)paper number 56(FAO56).The Penman-Monteith method was used to estimate ETo.Crop coefficients(Kc)from the phenomenological stages of rice were applied to adjust and estimate the actual evapotranspiration ETc through a water balance of the irrigation water requirements(IR).The results showed the BSBNR annual reference evapotranspiration(ETo)was estimated at 1967 mm.The lowest monthly value of ETo of 123 mm,was observed in August month,middle of the rainy season while the highest value 210 mm was observed in March within dry season.The crop evapotranspiration ETc and the crop irrigation requirements were estimated at 651 mm and 383 mm,respectively in rainy season and 920 mm and 1148 mm,respectively within a dry season.Irrigation projects of these seasons can then be scheduled for water use efficiency based on these findings.

Evaluation of CRU TS, GPCC, AgMERRA, and AgCFSR meteorological datasets for estimating climate and crop variables: A case study of maize in Qazvin Province, Iran

In the past few decades,meteorological datasets from remote sensing techniques in agricultural and water resources management have been used by various researchers and managers.Based on the literature,meteorological datasets are not more accurate than synoptic stations,but their various advantages,such as spatial coverage,time coverage,accessibility,and free use,have made these techniques superior,and sometimes we can use them instead of synoptic stations.In this study,we used four meteorological datasets,including Climatic Research Unit gridded Time Series(CRU TS),Global Precipitation Climatology Centre(GPCC),Agricultural National Aeronautics and Space Administration Modern-Era Retrospective Analysis for Research and Applications(AgMERRA),Agricultural Climate Forecast System Reanalysis(AgCFSR),to estimate climate variables,i.e.,precipitation,maximum temperature,and minimum temperature,and crop variables,i.e.,reference evapotranspiration,irrigation requirement,biomass,and yield of maize,in Qazvin Province of Iran during 1980-2009.At first,data were gathered from the four meteorological datasets and synoptic station in this province,and climate variables were calculated.Then,after using the AquaCrop model to calculate the crop variables,we compared the results of the synoptic station and meteorological datasets.All the four meteorological datasets showed strong performance for estimating climate variables.AgMERRA and AgCFSR had more accurate estimations for precipitation and maximum temperature.However,their normalized root mean square error was inferior to CRU for minimum temperature.Furthermore,they were all very efficient for estimating the biomass and yield of maize in this province.For reference evapotranspiration and irrigation requirement CRU TS and GPCC were the most efficient rather than AgMERRA and AgCFSR.But for the estimation of biomass and yield,all the four meteorological datasets were reliable.To sum up,GPCC and AgCFSR were the two best datasets in this study.This study suggests the use of meteorological datasets in water resource management and agricultural management to monitor past changes and estimate recent trends.

Planning of Cost Effective Water Harvesting in a Sub Basin of the Subarnarekha River in the State of West Bengal, India

Development and judicious management of available water resources play a key role for economic upliftment of any region. The agricultural pattern and social and demographic status in the upper basin of the Dulung Nala Stream （a tributary of the Subarnarekha River） in the western part of the State of West Bengal, India, reveals growing demand of water in the basin. The paper reports different management plans involving different types of water harvesting structures （and associated different types of water distribution systems） and different crop combinations and with benefit/cost ratios varying from 1.3 to 11.2 for the basin. The study points out that the judicious choice of both the water harvesting structure as well as the water distribution system is important. Proper planning of crop pattern is also to be emphasized for reaping maximum benefit. It further emphasizes that cost- benefit ratio cannot solely govern the choice of structure and that maximum utilization of catchmental water and thus enhancement of agricultural output （and also economic return from the catchment） i.e. quantum of benefit is also important. The water harvesting structures proposed in this study can be implemented in other semi-arid regions of India having almost the same climatic and socio-economic conditions.

Study on Rice Water Requirement of Liangping County under Climate Change Background

Under global climate change background,using daily meteorological data at Liangping ground meteorological station during 1961- 2012,we calculated crop water requirement and net irrigation water requirement during rice growth period in Liangping County,and analyzed its climate tendency rate. Results showed that climate tendency rate of crop water requirement during growth period of rice was only- 0. 007 mm /10 a; climate tendency rate of rainfall was- 0. 06 mm /10 a,but interannual change was relatively larger; climate tendency rate of net irrigation water requirement was 0. 011 mm /10 a. In the years when drought occurred,such as 2006 and 2011,both rice water requirement and net irrigation water requirement in Liangping were greatly higher than means over the years. Therefore,we should focus on drought pre-warning and risk management improving drought disaster prevention in Liangping in the future.

Risk assessment of agricultural green water security in Northeast China under climate change

Northeast China is an important base for grain production,dominated by rain-fed agriculture that relies on green water.However,in the context of global climate change,rising regional temperatures,changing precipitation patterns,and increasing drought frequency pose threats and challenges to agricultural green water security.This study provides a detailed assessment of the spatiotemporal characteristics and development trends of green water security risks in the Northeast region under the base period(2001-2020)and the future(2031-2090)climate change scenarios(SSP245 and SSP585)using the green water scarcity(GWS)index based on raster-scale crop spatial distribution data,Delta downscaling bias-corrected ERA5 data,and CMIP6 multimodal data.During the base period,the green water risk-free zone for dry crops is mainly distributed in the center and east of the Northeast region(72.4% of the total area),the low-risk zone is primarily located in the center(14.0%),and the medium-risk(8.3%)and high-risk(5.3%)zones are mostly in the west.Under SSP245 and SSP585 future climate change scenarios,the green water security risk shows an overall expansion from the west to the center and east,with the low-risk zone increasing to 21.6% and 23.8%,the medium-risk zone increasing to 16.0% and 17.9%,and the high-risk zone increasing to 6.9% and 6.8%,respectively.Considering dry crops with GWS greater than 0.1 as in need of irrigation,the irrigated area increases from 27.6%(base period)to 44.5%(SSP245)and 48.6%(SSP585),with corresponding increases in irrigation water requirement(IWR)of 4.64 and 5.92 billion m~3,respectively,which further exacerbates conflicts between supply and demand of agricultural water resources.In response to agricultural green water security risks,coping strategies such as evapotranspiration(ET)-based water resource management for dry crops and deficit irrigation are proposed.The results of this study can provide scientific basis and decision support for the development of Northeast irrigated agriculture and the construction planning of the national water network.