Development of optimal irrigation schedules and crop water production function for cassava: study over three major growing areas in India

A study was conducted to develop optimal irrigation schedules and crop water production function for cassava in the three major growing areas of India, viz., Salem (Tamil Nadu), Thiruvananthapuram (Kerala), and West Godavari (Andhra Pradesh). The irrigation schedules and water requirements were simulated using CROPWAT, and the model result was verified with field values in Thiruvananthapuram, one of the study areas. The results indicated the wider applicability of CROPWAT in calculating water requirement as well as developing irrigation schedules for cassava irrespective of the agro-climatic conditions. The optimal gross irrigation requirement simulated by CROPWAT was 362, 610, and 703 mm in Thiruvananthapuram, West Godavari, and Salem, respectively, based on the soil, crop and climatic parameters. The optimal schedules were also developed in the study locations using CROPWAT, and it can be used for further irrigation practices and plans to maximize water productivity. Also, the field experimental data in Thiruvananthapuram showed a quadratic relation between crop water requirement and yield (R-2 = 0.86). The derived crop water production function (CWPF), yield=-0.0013ETc2+1.138ETc-203.03\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$${\text{yield}} = - \,0.0013{\text{ET}}_{\text{c}}<^>{ 2} \, + \,1.138{\text{ET}}_{\text{c}} \, - \,203.03$$\end{document} provided yield of 39 x 10(3) kg ha(-1) of cassava corresponding to the simulated gross irrigation requirement of 362 mm in Thiruvananthapuram. Thus the CWPF together with the optimal schedules is a useful tool for water managers and farmers to develop appropriate irrigation plans in advance to mitigate the water scarcity as the result of climate change.