Estimation Of Crop Water Requirement Of Maize Crop Using FAO CROPWAT 8 .

Roja et al.Ind.J. Pure App.Biosci.(2020) 8(6), 222-228Availableonlineat www.ijpab.comISSN: 2582 – 2845ISSN: 2582 – 2845DOI: http://dx.doi.org/10.18782/2582-2845.8148Ind. J. Pure App. Biosci. (2020) 8(6), 222-228Research ArticlePeer-Reviewed, Refereed, Open Access JournalEstimation of Crop Water Requirement of Maize Crop Using FAOCROPWAT 8.0 ModelM. Roja1*, Ch. Deepthi2 and M. Devender Reddy31Ph. D Scholar, 2Assistant Professor, 3Professor,Department of Agronomy, M S Swaminathan School of AgricultureCenturion University of Technology and Management, Paralakhemundi, Odisha, India*Corresponding Author E-mail: roja@cutm.ac.inReceived: 5.05.2020 Revised: 9.06.2020 Accepted: 16.06.2020ABSTRACTTo use optimum amount of water for crops and reduce irrigation quantity, some form ofirrigation scheduling should be used by the farming community. Unscientific and injudiciousapplication of groundwater in this region resulted in depletion of the groundwater table. Toachieve effective utilization of the groundwater resources, there is a need to estimate the cropwater requirement for different crops at different management levels to accomplish effectiveirrigation management. Crop water requirements of maize crop in north coastal districts ofAndhra Pradesh was calculated using FAO Cropwat 8.0 a computer simulation model. Thesimulation study was conducted with the objectives of determining irrigation water requirementand irrigation scheduling for some major crops like maize and sugarcane. The Penman Monteith method was used for evapotranspiration calculation in the model. 80% of critical soilmoisture depletion was considered for irrigation. The model predicted the daily, decadal as wellas monthly crop water requirement at different growing stages of maize crop. The crop waterrequirement and irrigation requirement for maize crop 238.6 mm and 212.6 mm. Considering theabove findings it was suggested to use the Cropwat 8.0 model to predict the crop waterrequirements for different crops.Keywords: Cropwat 8.0, Crop water requirement, Maize, Gross irrigation and Net irrigation.INTRODUCTIONWater is the most important and critical inputfor agriculture and the demand for efficientuse of irrigation water for crops is intensifyingin view of changing climate. Irrigation watersupplies are decreasing day by day andscarcity has been seen in many areas of theworld. In India among all the consumersagriculture is the largest end user of waterwhere much effort has to be kept for itsefficient use in agriculture (Surendran et al.,2013).Cite this article: Roja, M., Deepthi, C. H., & Devender Reddy, M. (2020). Estimation of Crop WaterRequirement of Maize Crop Using FAO CROPWAT 8.0 Model, Ind. J. Pure App. Biosci. 8(6), 222-228.doi: http://dx.doi.org/10.18782/2582-2845.8148Copyright Nov.-Dec., 2020; IJPAB222

Roja et al.Ind. J. Pure App. Biosci. (2020) 8(6), 222-228Increased water demand brought about byrapid population growth has created thenecessity to increase food production throughthe expansion of irrigation and industrialproduction to meet basic human needs. Theprimary objective of irrigation is to applywater to maintain crop Evapotranspiration(ET) when precipitation is insufficient.Uneven and erratic distributions of monsoon,soil moisture stress prevailing during summerseason are considered as the major limitingfactors for lower yields. Precise information isrequired for crop water requirements,irrigation withdrawal as a function of crop, soiltype and weather conditions to achieveeffective planning. The rainfall andevapotranspiration ultimately determine waterbalance,cropwaterandirrigationrequirements of different crops of the region.Crop water requirement depend onclimatic conditions, crop area and type, soiltype, growing seasons and crop productionfrequencies (FAO, 2009 & George et al.,2000). Factors affecting the value of the cropwater requirement are the value of alue(ET0).Thecombination of two separate processes,whereby water is lost on one hand byevaporation from the soil surface and on theother hand by transpiration from a plant, iscalled evapotranspiration. However, a detailedstudy by comprising all the data on waterrequirement and availability is also notavailable under this study area (North coastaldistricts of Andhra Pradesh). Demand (cropwater requirements) of major crops in Northcoastal districts of Andhra Pradesh has beensorted with the long term climatic data byusing CROPWAT 8.0 model (FAO, 2009).This CROPWAT software program wasdeveloped by the Food and AgricultureOrganization (FAO) as a tool to assistirrigation engineers and agronomists inperforming the usual calculations for waterirrigation studies and mainly in themanagement and design of irrigation schemes(Salam et al., 2019). CROPWAT facilitates theestimation of the crop evapotranspiration, cropwater requirements and irrigation schedulewith different cropping patterns for irrigationCopyright Nov.-Dec., 2020; IJPABISSN: 2582 – 2845planning (Kuo et al., 2006; Gowda et al., 2013;Gouranga & Verma, 2005; Martyniak et al.,2006; Dechmi et al., 2003 & Zhiming et al.,2007).The main functions of CROPWAT area) equirementsandcropirrigationrequirements.b) To develop: irrigation schedules undervarious management conditions andscheme water supply.The FAO Penman-Monteith method is used inthe present study as it is recommended as thesole standard method for the computation ofthe reference evapotranspiration. The FAOPenman Monteith method requires radiation,air temperature, air humidity and wind speeddata. The irrigation schedule recommendationsfor various crops should be location-specific,considering the soil types and agro-ecologicalconditions (Solomon et al., 2018). CROPWAT8.0 is a significant practice used by scientistsfor the assessment of crop evapotranspiration,CWR, and irrigation scheduling.There is lack of information withrespect to North coastal districts of AndhraPradesh on Crop water requirements for maizegrown in this area which are calculatedthrough which there is a scope for schedulingirrigation for these crops. Hence an attempthas been made to calculate the crop waterrequirements and schedule the irrigation forthese crops.MATERIALS AND METHODS2.1 Study LocationThe study area was north coastal districts ofAndhra Pradesh (srikakulam, vizianagaramand visakhapatnam) with an area of 23537 km2and population of 9,338,177. This study arealies in the altitude from 17.68 0N to 18.29 0Nwith an longitude of 83.21 0 E - 83.89 0 E.2.2 Crop water requirementThe crop water requirement is the amount ofwater equal to what is lost from a croppedfield by the ET and is expressed by the rate ofET in mm/day. Estimation of CWR is derivedfrom crop evapotranspiration (ETc) which canbe calculated by the following equation.ETc Kc X ET0223

Roja et al.Ind. J. Pure App. Biosci. (2020) 8(6), 222-228Where, Kc is the crop coeffcient. It is the ratioof the crop ETc to the ET0, and it represents anintegration of the effects of four essentialqualities that differentiate the crop fromreference grass, and it covers albedo(reflectance) of the crop–soil surface, cropheight, canopy resistance, and evaporationfrom the soil. Due to the ET differences duringthe growth stages, the Kc for the crop will varyover the developing period which can bedivided into four distinct stages: initial, cropdevelopment, mid-season, and late season. Thereference evapotranspiration ET0 is calculatedby FAO Penman- Monteith method, usingdecision support software –CROPWAT 8.0developed by FAO, based on FAO Irrigationand Drainage Paper 56 (FAO, 2002). The FAOCROPWATprogram(FAO,2009)incorporates procedures for reference cropevapotranspirationandcropwaterrequirements and allow the simulation of cropwater use under various climate, crop and soilconditions (www.fao.org).2.3 Meteorological dataMeteorological data of ten years was collectedfrom Naira meteorological station located insrikakulam district with having latitude of18.38 0N, longitude of 83.90 0E and altitude of9m have been presented in table 1.Meteorological parameters used for calculationof ET0 are latitude, longitude and altitude ofthe station, maximum and minimumtemperature (oC), maximum and minimumrelative humidity (%), wind speed (km/day)and sunshine hours which was collected andthe average values have been fed to the model.Rainfall data collected from the same station isalso fed to the software which will generatethe effective rainfall data.2.4 Crop dataMajor crops grown in this region are rice,black gram, green gram, groundnut, sugarcane,sesame, pearl millet, mesta and finger millet.CROPWAT requires the crop data like, cropcoefficient, Kc values (initial, mid and lategrowth stages), rooting depth, length of plantgrowth stages, critical depletion and yieldresponse factor which were taken from FAOIrrigation and drainage paper 56. The yieldresponse factor (Ky) is the ratio of relativeyield reduction to relative evapo-transpirationCopyright Nov.-Dec., 2020; IJPABISSN: 2582 – 2845deficit that integrates the weather, crop andsoil conditions that make crop yield less thanits potential yield in the face of deficit evapotranspiration. Sowing and harvesting date weretaken according to the guide from agriculturaloperations over this area. Sowing dates weretaken at 15 days interval starting fromDecember 15th.2.5 Soil dataSoil type in this area is a red sandy loam. Thesoftware needs some general soil data liketotal available soil moisture, maximum raininfiltration rate, maximum rooting depth,initial soil moisture depletion and initialavailable soil moisture. These informationobtained from FAO manual 56.2.6. Irrigation ScheduleIrrigation scheduling determines the correctmeasure of water to irrigate and the correcttime for irrigation. The CROPWAT modelcalculates the ET0, crop water requirement andirrigation requirements to develop theirrigationschedulesunderdifferentadministration conditions and water supplyplans.RESULTS AND DISCCUSSIONEstimation of the crop water requirement wascarried out by using the historical weather dataof the Naira, srikakulam district (Table 2). Thedata which was entered in the CROPWATsoftware included the details like country(India), climatic station (Naira), type of crop,date of cultivation, and soil type (sandy loam).Automatically software will compute the ET0,effective rainfall, and total irrigationrequirement for the respective crop once thedata is fed to the model. For the application ofirrigation, the critical soil moisture depletionwas considered at 80%. The model predictedthe daily, decadal as well as monthly cropwater requirement at different growing stagesof maize crop. The crop water requirement forthe maize crop 238.6 mm and irrigationrequirement was of 212.6 mm respectively.(Table 3 and Fig.1) It has been found that thereis no yield reduction (Table 4 ) in maize cropwith maximum rainfall efficiency at 80%critical depletion and refilling the soil to fieldcapacity whereas, The detailed results of totalgross irrigation, total net irrigation, actual224