Abstract
Brackish water has been widely used to irrigate crops to compensate for insufficient freshwater water supply for agricultural use. The goal of this research was to determine an efficient brackish water use method to increase irrigation efficiency and reduce N2O emission. To this end, we conducted a field experiment with four salinity levels of irrigation water (1.1, 2.0, 3.5, and 5.0 g·L−1 with drip irrigation) at Hetao Irrigation District (Inner Mongolia, China) in 2017 and 2018. The results show that irrigation with 3.5–5.0 g·L−1 water salinity increased the soil salinity compared with irrigation using 1.1–2.0 g·L−1 water salinity. The soil water content with 5.0 g·L−1 brackish water irrigation was significantly higher than with 1.1–3.5 g·L−1 water salinity due to the effect of salinity on crop water uptake. The overall soil pH increased with the increase in irrigation water salinity. Saturated soil hydraulic conductivity decreased with the increase in irrigation water salinity. These results indicate that brackish water irrigation aggravates the degree of soil salinization and alkalization. The soil N2O cumulative flux resulting from irrigation with 5.0 g·L−1 water salinity was 51.18–82.86% higher than that resulting from 1.1–3.5 g L−1 water salinity in 2017, and was 32.38–44.79% higher than that resulting from 1.1–2.0 g·L−1 in 2018. Irrigation with brackish water reduced maize yield, and the reduction in yield in 2018 was greater than that in 2017, but irrigation with 2.0 g·L−1 brackish water did not significantly reduce maize yield in 2017. These results suggest that reducing the salinity of irrigation water may effectively reduce soil N2O emission, alleviate the degree of soil salinization, and increase crop yield.
Highlights
Situated in Inner Mongolia, Hetao Irrigation District (HID) is an important commodity grain-producing area in Northwest China
The irrigation water salinity had a significant effect on the soil water content (p < 0.05)
We found that the soil N2 O emission increased with the increase in irrigation water salinity
Summary
Situated in Inner Mongolia, Hetao Irrigation District (HID) is an important commodity grain-producing area in Northwest China. Due to the region’s arid climate, agricultural production has always depended on local Yellow River irrigation. To promote agricultural production, mulched planting technology, due to its heat preservation, water saving, and yield increases, has been widely promoted in HID. With the development of the economy, the use of industrial water and domestic water in HID is increasing. Because of policy regulation, the amount of water diverted from the Yellow River will decrease by 20% (from 5 billion m3 to 4 billion m3 ) in the 10 years [1]. The problem of insufficient agricultural water use is becoming increasingly serious. It is imperative to develop methods for efficient water-saving irrigation. Alternative water sources for irrigation should be found for the sustainable development of agriculture in HID
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