Runoff nitrogen from a large sized paddy field during a crop period

• Published in: Agricultural water management Vol. 87; no. 2; pp. 217 - 222
• Main Authors: Yoshinaga, Ikuo, Miura, Asa, Hitomi, Tadayoshi, Hamada, Koji, Shiratani, Eisaku
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 24.01.2007; Elsevier Science; Elsevier
• Series: Agricultural Water Management
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Farmland; Fundamental and applied biological sciences. Psychology; Net yield; Non-point source; Soil and water pollution; Soil science; Water balance; Asia; Honshu; Japan; Japan, Honshu, Shiga Prefect., Biwa L; Farmland; Non-point source; Net yield; Water balance; Cultivated field; Large dimension; Fresh water; Growing season; Irrigation water; Inorganic element; Temperate zone; Eutrophication; Freshwater environment; Aquatic environment; Water analysis; Arable land; Flood irrigation; Rural area; Time interval; Chemical composition; Paddy field; Mathematical model; Non metal; Pollution by agriculture; Load; Hydraulic model; Runoff water; Nitrogen; Agroecosystem; Group VA element; Pollutant; Diffuse source; Hydrochemistry; Runoff; Surface water; Water quality; Pollution source; Water pollution; Yield; Computing method
• ISSN: 0378-3774; 1873-2283
• DOI: 10.1016/j.agwat.2006.06.020

Nutrient load management is an important environmental issue because nutrient loads from farmlands degrade surface waters as a result of anthropogenic eutrophication. Nitrogen load from a large sized paddy field during the crop period was examined from the results of field measurements carried out in 2004. The 1.5 ha paddy field was located east of Biwa Lake. Irrigation water volume and ponded water depth were continuously observed. Field measurements were carried out at least once a week to analyze total nitrogen (TN) concentration in the irrigation water and ponded water. Daily inflow and outflow of nitrogen was obtained by multiplication of the nitrogen concentration and transported water volume, consisting of irrigation, precipitation, evapotranspiration, percolation and surface discharge. Water outflow volume was calculated by a tank model that consisted of three small tanks connected to represent ponded water depth differences in the large paddy field. The calculated nitrogen load was 18.8 kg ha −1, with 7.2 kg ha −1 from surface drainage and 11.6 kg ha −1 from percolation loss. The runoff nitrogen value of 18.8 kg ha −1 was within the range of the reported values investigated in a medium-sized paddy field. The observed value was close to the value for a low percolation flux paddy field where less irrigation water has been applied. These results suggest that less irrigation water keep runoff nitrogen low. This also indicates that irrigation water management can reduce nitrogen load from large sized paddy fields.