Field kites: Crop-water production functions and the timing of water application for supplementary irrigation

Abstract:

Agricultural production is directly related to water management and water supply. The temporal distribution of water use throughout the growing season can significantly influence crop yield, and the facility to manage both the timing and amount of irrigation water may result in higher yields. The crop-water production function quantitatively evaluates the relationship between seasonal water use and crop yield. Previous efforts have attempted to describe and formalize the crop-water production function as a single-variable function of seasonal water use. However, these representations do not account for the effects of temporal distribution of water use and trivialize the associated variability in yields by assuming an optimized or arbitrary temporal distribution of soil moisture. This over-simplification renders the function inappropriate for recommendations related to irrigation scheduling, water management, economically optimal irrigation, water and agricultural productivity, and assessing the role of full and supplementary irrigation. We propose field kites, a novel representation of the crop-water production function that explicitly acknowledges crop yield variability as a function of both seasonal water use and associated temporal distributions of water use. Field kites are a tool that explicitly considers the farmers’ capacity to manage their water resources, to more appropriately evaluate the optimal depth of irrigation water under water-limiting conditions. The field kite for winter wheat is presented both generally and cultivar- and climate-specific for Western Canada. The field kites are constructed using AquaCrop and previously validated cultivar-specific variables. Field kites provide the tools for water authorities and policy makers to evaluate agricultural production as it relates to farm water management, and to determine appropriate policies related to developing and supporting the necessary irrigation infrastructure to increase water productivity.