Abstract
Field research was done in two consecutive years to optimize deficit irrigation under different crop densities (low, medium, and high) using the ridge and furrow rainfall harvesting (RFRH) system. We demonstrate that applying deficit irrigation (375 m3 ha−1) at the flowering stage of maize grown at medium density (M: 75000 plant ha−1) under the RFRH system (MIF) can improve soil water storage (0–200 cm) at the bell, filling and flowering stages. MIF increased biomass by 10% and grain yield by 21%, thereby achieving a 17% increase in water use efficiency (WUE) and a 22% increase in precipitation use efficiency (PUE) compared with conventional flat planting (CKM). MIF also improved irrigation water use efficiency (IWUE) (9%) and irrigation water productivity (IWP) (46%) compared with no-irrigation under the RFRH system (MI0). We observed that applying deficit irrigation (750 m3 ha−1) at the bell and flowering stage (IBF) had positive effects on dry matter, leaf area, and evapotranspiration, but there were no significant increases in IWUE, IWP, WUE, biomass and grain yield compared with maize grown under IF at low, medium and high plant densities. The average net profit over the two years was 34% higher for MIF compared with the CKM treatment.
Highlights
Irrigation water supplies are declining in many semi-arid regions of world
Under all treatments in 2015 there were no significant differences in Soil water storage (SWS) (0–200 cm) from the time of sowing until the jointing stage (0–60 days after planting (DAP)), but SWS decreased from sowing until the filling stage (0–128 DAP)
Compared with the MIB and MIBF treatments, the irrigation water productivity (IWP) of the MIF treatment was significantly improved by 3.86 kg m−3 (80%), and 3.07 kg m−3 (89%), respectively. These results suggest that increasing planting density in the ridge and furrow rainwater harvesting (RFRH) system from low to medium could improve water use efficiency (WUE), precipitation use efficiency (PUE), irrigation water use efficiency (IWUE) and IWP, whereas increasing planting density from medium to high results would likely lead to a reduction in WUE, PUE and IWUE
Summary
Irrigation water supplies are declining in many semi-arid regions of world. Some of the reasons for this decline include extended drought periods, uneven rainfall distribution and decline in groundwater levels[1]. To improve the management and consumption of soil water, enhancing the irrigation water productivity (IWP) of crops grown in semi-arid regions, such as maize, is needed[4,5]. There have been many studies on water-saving agricultural practices, little information is available on the effect of reducing irrigation by fully utilizing the available rainfall under a RFRH system on crops grown under different plant densities. For arid and semi-arid regions, crop yield under limited irrigation depends on the amount of accessible water, which consists of rainfall and available soil moisture, and the timing of water availability[15,16]. In recent years, increasing planting density has been found to be a simple and effective method for increasing maize yield in semi-arid regions[20]. Little information is available about optimal maize planting densities for deficit irrigation when grown under the RFRH system
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