Abstract
The use of water-saving irrigation techniques has been encouraged in rice fields in response to irrigation water scarcity. Straw return is an important means of straw reuse. However, the environmental impact of this technology, e.g., nitrogen leaching loss, must be further explored. A two-year (2017–2018) experiment was conducted to investigate the vertical migration and leaching of nitrogen in paddy fields under water-saving and straw return conditions. Treatments included traditional flood irrigation (FI) and two water-saving irrigation regimes: rain-catching and controlled irrigation (RC-CI) and drought planting with straw mulching (DP-SM). RC-CI and DP-SM both significantly decreased the irrigation input compared with FI. RC-CI increased the rice yield by 8.23%~12.26%, while DP-SM decreased it by 8.98%~15.24% compared with FI. NH4+-N was the main form of the nitrogen leaching loss in percolation water, occupying 49.06%~50.97% of TN leaching losses. The NH4+-N and TN concentration showed a decreasing trend from top to bottom in soil water of 0~54 cm depth, while the concentration of NO3−-N presented the opposite behavior. The TN and NH4+-N concentrations in percolation water of RC-CI during most of the rice growth stage were the highest among treatments in both years, and DP-SM showed a trend of decreasing TN and NH4+-N concentrations. The NO3−-N concentrations in percolation water showed a regular pattern of DP-SM > RC-CI > FI during most of the rice growth stage. RC-CI and DP-SM remarkably reduced the amount of N leaching losses compared to FI as a result of the significant decrease of percolation water volumes. The tillering and jointing-booting stages were the two critical periods of N leaching (accounted for 74.85%~86.26% of N leaching losses). Great promotion potential of RC-CI and DP-SM exists in the lower reaches of the Yangtze River, China, and DP-SM needs to be further optimized.
Highlights
Water plays a critical role in stable agricultural production, especially for paddy rice, which has greater water requirements [1,2]
For the flood irrigation (FI) treatment, the water depth was maintained throughout almost the whole rice growth stage in both years, except for the period of field sunning in the late tillering stage and the period of ripening stage
About two-thirds of the total rice growth season was in non-flooding conditions under rain-catching and controlled irrigation (RC-controlled irrigation (CI)) treatment in both years and about three-fourths of the total rice growth season was in non-flooding condition under drought planting with straw mulching (DP-SM) treatment
Summary
Water plays a critical role in stable agricultural production, especially for paddy rice, which has greater water requirements [1,2]. Rice is one of the most important food crops in China. The rice production of China ranks first in the world, occupying 28% of the world’s total rice production [3]. Water 2019, 11, 868 water in agricultural production [4,5]. Several water-saving irrigation technologies based on alternate wetting and drying (AWD), such as saturated soil culture, controlled irrigation, intermittent irrigation, aerobic rice, controlled irrigation and drainage, have been developed for rice production in. The environmental effects of these water-saving irrigation technologies are not well understood
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