The Coupled Effect of Precipitation and Fertilization on Nitrogen Loss Via Surface Runoff from Paddy Fields

Abstract

【Objective】 Nitrogen loss from soils is a pervasive environmental issue facing agricultural production in many countries. In this paper, we studied the combined effect of rainfall and fertilization on nitrogen loss via surface runoff from paddy fields in attempts to improve nitrogen management and reduce the nonpoint source pollution of rice production in Southern China. 【Method】 The experiment was conducted from 2019 to 2021 in a paddy field in Zhejiang province. It consisted of four nitrogen treatments: conventional nitrogen fertilization (N18), reduced nitrogen fertilization (N15), organic fertilization (OF). Without fertilization was the control. In the experiment, we measured surface runoff, total nitrogen concentration in the surface runoff. The rainfall data were obtained from a weather station on the experimental site. 【Result】 ① Annual rainfall and annual nitrogen loss were closely correlated, but linear regression analysis showed that daily rainfall and total nitrogen did not correlate significantly. Considering the delay between rainfall and nitrogen loss vial the surface runoff can make piecewise average daily rainfall positively correlated to nitrogen loss, with the regression coefficient ≥0.36. ② The effect of fertilization on nitrogen loss from the runoff was ranked in the order of N18>N15>OF>CK. ③ Structural equation showed that, when considering the delay between rainfall and nitrogen loss, the piecewise average daily rainfall, the runoff volume, rainfall interval, the interval between rainfall and fertilization, fertilization amount, and fertilizer types were the factors affecting nitrogen loss, with their standardized total effect being 0.264, -0.126, 0.078, 0.033, and -0.038, respectively. The rainfall affected nitrogen loss more than the fertilization, and the piecewise average daily rainfall and rainfall interval were key factors affecting nitrogen loss. 【Conclusion】 For rice-wheat rotation cultivation in Zhejiang Province, a short rainfall interval affected nitrogen loss via surface runoff from paddy fields more than an increase in rainfall. Applying organic fertilizer in the wet season can reduce nitrogen loss from the runoff.

Keywords

• paddy fields
• nitrogen loss
• non-point source pollution
• fertilization
• rainfall