Estimation of water requirement for soybean (Glycine max) and wheat (Triticum aestivum) under vertisols of Madhya Pradesh

The present study was undertaken to evaluate various methods of estimating evapotranspiration to predict water requirement of soybean and wheat crops for nine selected districts of Madhya Pradesh under vertisols. Four methods (Penmann-Montieth, Hargreaves, SCS-Blaney-Criddle and Thornthwaite) of reference evapotranspiration (ET0) estimation were compared for assessing their predictive capability for Bhopal and Indore districts using meteorological data. Reference evapotranspiration was estimated by using Penmann-Montieth method for two districts (Bhopal and Indore) for which data on solar radiation were available and Hargreaves method for remaining seven districts (Chhindwara, Dhar, Guna, Hoshangabad, Jabalpur, Khandawa and Raisen). Crop water requirements were determined through field experiments conducted during 2008 to 2010 for soybean and 2008-09 to 2010-11 for wheat crops using non-weighing type lysimeters at research farm of Central Institute of Agricultural Engineering, Bhopal. The study revealed that among the four methods, Hargreaves method estimated ET0 values with minimum deviation (4.24%) for Bhopal as compared to Penmann-Monteith. The water requirement of soybean and wheat estimated by Penmann-Monteith method was in close agreement (-2.58% and 9.26% deviation) with the measured average water requirement (401.6 and 352.2 mm) respectively followed by Hargreaves method for Bhopal district. It is also inferred that in absence of solar radiation data Hargreaves method could be considered for predicting water requirement of soybean and wheat crops. These water requirement values are useful for effective planning of irrigation scheduling of the soybean and wheat crops in the State.