Abstract
Precision irrigation technologies are being widely promoted to resolve challenges regarding improving crop productivity under conditions of increasing water scarcity. In this paper, the development of an integrated modelling approach involving the coupling of a water application model with a biophysical crop simulation model (Aquacrop) to evaluate the in-field impacts of precision irrigation on crop yield and soil water management is described. The approach allows for a comparison between conventional irrigation management practices against a range of alternate so-called ‘precision irrigation’ strategies (including variable rate irrigation, VRI). It also provides a valuable framework to evaluate the agronomic (yield), water resource (irrigation use and water efficiency), energy (consumption, costs, footprint) and environmental (nitrate leaching, drainage) impacts under contrasting irrigation management scenarios. The approach offers scope for including feedback loops to help define appropriate irrigation management zones and refine application depths accordingly for scheduling irrigation. The methodology was applied to a case study in eastern England to demonstrate the utility of the framework and the impacts of precision irrigation in a humid climate on a high-value field crop (onions). For the case study, the simulations showed how VRI is a potentially useful approach for irrigation management even in a humid environment to save water and reduce deep percolation losses (drainage). It also helped to increase crop yield due to improved control of soil water in the root zone, especially during a dry season.
Highlights
In order to meet future food demands from a rising global population whilst minimising any environmental impact, a commensurate increase in agricultural productivity coupled with improvements in water and nutrient efficiency will be necessary (Kumar et al 2016; Monaghan et al 2013)
An integrated modelling approach involving the coupling of a deterministic water/irrigation application model (WAM) with a biophysical crop model (Aquacrop) (Steduto et al 2012) was developed and used to simulate the impacts of irrigation heterogeneity caused, for example, due to wind drift, irrigation system pressure variation and/or sprinkler overlapping on crop growth and yield at the field scale
It provides the potential for including feedback loops to help define irrigation management zones (IMZ) corresponding to areas within a single field which could be delimited for variable water and nutrient and water management strategies
Summary
In order to meet future food demands from a rising global population whilst minimising any environmental impact, a commensurate increase in agricultural productivity (yield) coupled with improvements in water and nutrient efficiency will be necessary (Kumar et al 2016; Monaghan et al 2013). In this context, irrigated agriculture will play a critical role supporting increased production in arid and semi-arid regions, and enhancing crop quality through supplemental irrigation in temperate or humid regions (Daccache et al 2014a, b; De Paz et al 2015). Taking into account current pressures on water resources and projected future increases in irrigated area, the agricultural sector needs to do more with less, increasing water productivity (t ha-1) by improving water efficiency and producing more ‘crop per drop’ (Monaghan et al 2013)
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