Abstract
Irrigated cotton (Gossypium hirsutum L.) growers in the Murray-Darling Basin (MDB) of Australia, are challenged by limited water availability. This modelling-study aimed to determine if deficit irrigation (DI) practices can potentially improve water use efficiency (WUE) for furrow irrigation (FI), overhead sprinkler irrigation (OSI) and subsurface drip irrigation (SDI) systems. We validated the Agricultural Production System sIMulator (APSIM) against observed cotton lint yield and crop biomass accumulation for different management practices. The model achieved concordance correlation coefficients of 0.93 and 0.82 against observed cotton crop biomass accumulation and lint yields, respectively. The model was then applied to evaluate the impacts of different levels of DI on lint yield, WUE across cotton growing locations in the MDB (Goondiwindi, Moree, Narrabri, and Warren), during the period from 1977 to 2017. The different levels of DI for the FI system were no irrigation, full irrigation (TF) and irrigated one out of four, one out of three, one out of two, two out of three and two out of four TF events. For the OSI and SDI systems, DI levels were no irrigation, TF, 20% of TF, 40% of TF, 60% of TF and 80% of TF. Lint yield was maximised under the OSI and SDI systems for most locations by applying 80% of TF. However; modelling identified that WUE was maximised at 60% of full irrigation for OSI and SDI systems. These results suggest there are significant gains in agronomic performance to be gained through the application of DI practices with these systems. For FI, DI had no benefit in terms of increasing yield, while DI showed marginal gains in terms of WUE in some situations. This result is due to the greater exposure to periodic water deficit stress that occurred when DI practices were applied by an FI system. The results suggest that in the northern MDB, water savings could be realised for cotton production under both OSI and SDI systems if DI were adopted to a limited extent, depending on location and irrigation system.
Highlights
90% of the Australian cotton (Gossypium hirsutum L.) crop is grown in the Murray-Darling Basin (MDB), in northern New South Wales (NSW) and southern Queensland (QLD) in both irrigated and dryland cropping systems [1,2,3]
Our results showed that modelled lint yield, water use efficiency (WUE) and marginal water use efficiency (MWUE) under the furrow irrigation (FI) system were lower than for the subsurface drip irrigation (SDI) (c.a. 27%, 8%, and 10% lower respectively for the TF treatment) and overhead sprinkler irrigation (OSI) (c.a. 25%, 8%, and 7% lower respectively for the TF treatment) systems (Figures 4–6)
Differences in lint yield and WUE, induced by the use of deficit irrigation (DI) practices under three irrigation systems of FI, OSI and FI have been modelled with Agricultural Production System sIMulator (APSIM) across four Australian cotton growing locations, using the APSIM cotton model
Summary
90% of the Australian cotton (Gossypium hirsutum L.) crop is grown in the Murray-Darling Basin (MDB), in northern New South Wales (NSW) and southern Queensland (QLD) in both irrigated and dryland cropping systems [1,2,3]. 83% of cotton grown within the MDB is irrigated, with the remaining 27% being dryland [4,5,6]. Water availability is one of the most important determinants of the total area of cotton grown under irrigation in the MDB [8,9]. The OSI and SDI systems allow cotton crops to be grown with relatively less irrigation water, which can result in higher water use efficiency (WUE) and higher marginal water use efficiency (MWUE) [16,17]
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