Effects of Controlled Irrigation and Drainage on Nitrogen and Phosphorus Concentrations in Paddy Water

Shi-Kai Gao,Mei Wang,Rong Guo,Dong-Li She,Guang-Cheng Shao,Rui-Zhe Cao,Shuang-En Yu,Ji-Hui Ding,Shao-Feng Yan

doi:10.1155/2016/2576015

Abstract

Controlled irrigation and drainage (CID) has received attention for improving water quality. Under CID condition, water stress is frequently experienced in two contexts: first drought and then flooding (FDTF) and first flooding and then drought (FFTD). This study aimed to investigate the effects of FDTF and FFTD on nitrogen (N) and phosphorus (P) dynamics in paddy water at different growth stages. The effects of water stress on the migration and transformation of N and P were also investigated. Results showed that CID can decrease N and P concentrations in surface water.NH4+-Nwas the major form of N in surface drainage and percolation water. Mean total phosphorus (TP),NH4+-N, andNO3--Nconcentrations were significantly higher than in FFTD during the growth stage. MeanNH4+-N,NO3--N, and TP concentrations were significantly higher in percolation water under flooding stress than those under drought stress at growth stage, except for mean TP concentrations at milky stage (stage IV). Meanwhile, flooding can sharply increase theNH4+-N,NO3--N, and TP concentrations in percolation water after drought. Thus, without CID, the considerably highNH4+-N,NO3--N, and TP concentrations via runoff and leaching can be responsible for the eutrophication of water bodies in the vicinity of paddy fields during the rice growing season when water stress transforms from drought into flooding.

Highlights

Agricultural nonpoint source pollution is a major environmental issue in many countries with intensive farming systems [1, 2]
Compared with the first day of flooding at each stage, the NH4+-N concentrations for the first flooding and then drought (FFTD) surface water were decreased by 50.9%, 42.2%, 54.74%, and 42.1% at the end of flooding; the NH4+-N concentrations for the first drought and then flooding (FDTF) surface water were decreased by 55.2%, 53.1%, 51.0%, and 32.5%
The mean total phosphorus (TP) concentrations were significantly higher in percolation water under flooding stress than under drought stress during the growth stage, except at stage IV

Summary

Introduction

Agricultural nonpoint source pollution is a major environmental issue in many countries with intensive farming systems [1, 2]. Nitrogen (N) and phosphorus (P) loads from unmanaged agricultural nonpoint sources [2], such as runoff and leaching from paddy fields, have been associated with water body eutrophication of many lakes and streams [3, 4]. Paddy rice is one of the most important food crops in Southern China [5,6,7]. The utilization of N is relatively low in irrigated rice because of rapid N losses through surface runoff, denitrification, leaching, and ammonia volatilization [8]. P is relatively stable in soils and runoff and leaching are the major routes of excessive P losses [10]

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Conclusion