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| DOI：10.13522/j.cnki.ggps.20180217 |
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| Loss of Nitrogen and Phosphorus From Soil and Surface Water in Flooded Cropland |
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YANG Jiwei, TANG Guangmin, LI Ruzhong, YUAN Xianjiang, YUAN Hongwei, JIANG Shangming
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1.Water Resources Research Institute of Anhui Province and Huaihe River Commission, Ministry of Water Resources, Bengbu 233000, China; 2. Key Laboratory of Water Conservancy and Water Resources of Anhui Province, Bengbu 233000, China; 3. Department of Resource and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
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| Abstract: |
| 【Objective】 This paper studies the loss of nitrogen and phosphorus from soil and surface water in flooded cropland in attempts provide data to help design drainage strategies. 【Method】 The experiment was conducted in a lysimeter filled with undisturbed soil and grown with soybean. During the experiment, nitrogen, phosphorus, pH and Eh in the soil as well as nitrogen and phosphorus in the overlying surface water were measured. 【Result】 The loss of N and P from the soil increased with the duration of surface ponding; compared with their values prior to flooding, the average TN and TP loss from the soil was approximately 7.63% and 3.17% at ease of the flooding respectively, in which alkali-hydrolyzable nitrogen reduced by 17.84% while Olsen-P increased by 8.65%. Following the flooding, the concentration of TN, NH4+-N and NO3--N in the surface water increased fast, reaching 0.405, 0.192 and 0.209 mg/L respectively one day after the flooding. Two to four days after the flooding, TN concentration still increased with time but at a decreasing rate with the concentration of NH4+-N and NO3--N reduced to 0.226 mg/L. Four days after the flooding eased, both TN and NH4+-N increased while NO3--N decreased. The ratio of inorganic nitrogen to TN decreased from 98.5% to 54.4% during the flooding duration, while the phosphorus content increased monotonically. The TP content was 0.615 mg/L at the end of flooding with SRP accounting for 80.5%~91.6%. Both pH and Eh dropped following the flooding, thereby enhancing migration of nitrogen and phosphorus from the soil to the overlying surface water. 【Conclusion】 Considering N and P loss from soil and crop yield, timely drainage is essential to reduce nutrient loss without scarifying yield. For the case studied in this work, instigating drainage three days after the flooding appears to be the best compromise. |
| Key words: flooding test; farmland soil; nitrogen and phosphorus loss; controlled drainage |
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