Determination of the water requirement and crop coefficient values of sugarcane by field water balance method in semiarid region

Abstract

Sugarcane is a major agro-industrial crop in semiarid regions and generally has high evapotranspiration. Standardized reference evapotranspiration (ET) and location specific crop coefficients are used to estimate crop evapotranspiration. However, precise information on crop coefficient (Kc) is a major impediment in semiarid environments. Field studies were conducted during two seasons of 2015 and 2016 in clay soils to determine crop evapotranspiration and crop coefficients (Kc) of sugarcane for semiarid India.The experimental area was cultivated with irrigation applied at 7–10 days interval by a drip irrigation system in addition to rainfall and the irrigation scheduling was based on field water balance approach. The crop evapotranspiration was determined by field water balance, reference evapotranspiration (ETo) by the Penman-Monteith approach while crop coefficient were computed through the standard FAO-56 methodology.On an annual basis, the total reference evapotranspiration (ETo) and crop evapotranspiration (ETc) were 1318−1426 mm and 1291−1388 mm respectively. Two years average sugarcane crop evapotranspiration estimated by field water balance method was 1339 mm year−1. The irrigation water requirement andeffective rainfall was 991 mm year-1 and 424 mm year-1 respectively. Two years results showed that there was a notable symmetry between Kc obtained from field water balance measurements and FAO-56 reported Kc. The determined Kc values for tillering, grand growth and maturity stages of sugarcane were 0.70, 1.20 and 0.78, respectively. The Kc values were found 25.5 %, 4 % and 20.4 % less during the tillering, grand growth and maturity stage respectively over the FAO-56 Kc values. The 2nd order polynomial equation was fitted with crop coefficient as the dependent variables and ratio of days after transplanting to total crop period as the independent variable. The daily values of Kc from equation is very useful towards efficient management of irrigation water in terms of making a Decision Support System, Soil Moisture based Crop Yield Modeling, Crop Water Requirement based Computer programme or Mobile Application, Automation of irrigation system in the major sugarcane growing countries of semi arid regions.