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Chinese Agricultural Science Bulletin ›› 2023, Vol. 39 ›› Issue (9): 85-91.doi: 10.11924/j.issn.1000-6850.casb2022-0336

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The Responses of Nitrogen Loss from Paddy Field to Simulated Rainfall and Restored Materials

MIAO Huan(), QIAO Yunfa, LI Qing, MIAO Shujie()   

  1. School of Applied Meteorology, Nanjing University of Information Science & Technology, Nanjing 210044
  • Received:2022-04-21 Revised:2022-07-22 Online:2023-03-25 Published:2023-03-23

Abstract:

To explore effective measures to reduce the nitrogen loss from paddy field, the study was carried out to reveal the response of nitrogen loss from paddy field with different restored materials under heavy rain condition. Based on pot experiment and artificial rainfall simulation, the experiment set up two rainfall intensities (4 and 80 mm/h) and three surface water depths (2, 5 and 8 cm). Straw and biochar were used as restored materials to study the effects of rainfall intensity and restoration measures on nitrogen loss in paddy field with time and at different rice growth stages. The results showed that under the same amount of rainfall condition, after the simulated 4 mm/h rainfall, the concentration of NH4+-N in the surface water with straw and biochar addition was 15.1% and 59.4% lower than that of control treatment (NPK), respectively. However, the concentration of NO3--N in the straw and biochar added surface water was slightly higher than that of the control treatment. After a short-time heavy rainfall (80 mm/h), the concentration of NH4+-N in surface water was decreased by 55.4% and 63.9% by straw and biochar addition, respectively, and the concentration of NO3--N was decreased by 38.7% and 48.1%, respectively. Under the two rainfall intensities, the concentrations of NO3--N and NH4+-N in the surface water were the highest on the first day after rainfall, then began to decrease, and the lowest level was observed on the fifth day. In general, the concentration of NO3--N in the surface water of paddy field was lower than that of NH4+-N, but both of them showed gradual decrease trends with time. The concentrations of NO3--N and NH4+-N in the surface water were decreased with water layer increase after rainstorm. These results indicate that the addition of straw and biochar could effectively retain nitrogen nutrient in paddy soil and reduce the risk of nutrient loss. In comparison, biochar addition is better than straw addition. If the drainage time is delayed after rainfall, the nitrogen loss in the paddy field could be effectively reduced, and one week after fertilization is a critical period to control the nitrogen loss from paddy soil.

Key words: rainstorm, paddy field, nitrogen loss, straw returning, biochar