Abstract
Abstract. Consumptive water footprint (WF) reduction in irrigated crop production is essential given the increasing competition for freshwater. This study explores the effect of three management practices on the soil water balance and plant growth, specifically on evapotranspiration (ET) and yield (Y) and thus the consumptive WF of crops (ET / Y). The management practices are four irrigation techniques (furrow, sprinkler, drip and subsurface drip (SSD)), four irrigation strategies (full (FI), deficit (DI), supplementary (SI) and no irrigation), and three mulching practices (no mulching, organic (OML) and synthetic (SML) mulching). Various cases were considered: arid, semi-arid, sub-humid and humid environments in Israel, Spain, Italy and the UK, respectively; wet, normal and dry years; three soil types (sand, sandy loam and silty clay loam); and three crops (maize, potato and tomato). The AquaCrop model and the global WF accounting standard were used to relate the management practices to effects on ET, Y and WF. For each management practice, the associated green, blue and total consumptive WF were compared to the reference case (furrow irrigation, full irrigation, no mulching). The average reduction in the consumptive WF is 8–10 % if we change from the reference to drip or SSD, 13 % when changing to OML, 17–18 % when moving to drip or SSD in combination with OML, and 28 % for drip or SSD in combination with SML. All before-mentioned reductions increase by one or a few per cent when moving from full to deficit irrigation. Reduction in overall consumptive WF always goes together with an increasing ratio of green to blue WF. The WF of growing a crop for a particular environment is smallest under DI, followed by FI, SI and rain-fed. Growing crops with sprinkler irrigation has the largest consumptive WF, followed by furrow, drip and SSD. Furrow irrigation has a smaller consumptive WF compared with sprinkler, even though the classical measure of "irrigation efficiency" for furrow is lower.
Highlights
One of the important prospects for relieving increasing water scarcity is to reduce the consumptive water use in the agricultural sector, which makes up the largest share in global freshwater consumption (Hoekstra and Mekonnen, 2012)
The yields for ET less than 200 mm in Fig. 2a, b and c are under rain-fed conditions and high-deficit irrigation, with synthetic mulching practice
This paper provides the first detailed and comprehensive study regarding the potential for reducing the consumptive water footprint (WF) of a crop at field level by changing management practice such as irrigation technique, irrigation strategy and mulching practice
Summary
One of the important prospects for relieving increasing water scarcity is to reduce the consumptive water use in the agricultural sector, which makes up the largest share in global freshwater consumption (Hoekstra and Mekonnen, 2012). The focus is to decrease the field evapotranspiration (ET) over the growing period per unit of yield (Y ), a ratio that is called the consumptive water footprint (WF) (Hoekstra et al, 2011). Decreasing this ET/Y ratio is the same as increasing the inverse (Y /ET), which is called the water productivity (WP) (Amarasinghe and Smakhtin, 2014; Molden et al, 2010). Management practices that influence soil moisture include irrigation techniques, irrigation strategies and mulching practices. The mulching practice determines soil cover and in this way influences non-productive evaporation
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