Characteristics of Effluents of Nitrogen and Phosphorous in Paddy Fields during The Paddling and Transplanting Season

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  • 代かき田植時期のN, P成分の流出特性について
  • シロカキ タウエ ジキ ノ N P セイブン ノ リュウシュツ トクセイ ニ

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Abstract

It is well known that the outflow loads of N (nitrogen) and P (phosphorus) from paddy fields during the puddling and transplanting season are large. For three years, the authors made close investigations to clarify the characteristics of the nitrogen and phosphorus effluents.<BR>The results are summarized as follows: When the puddling and transplanting season (15 days) is divided into three periods of 5 days each, the highest concentrations of N were found in the early days of the first period, this is the period when farmers allow irrigation water to flow in pudding. One reason for the highest concentration in this period is that organic N and ammonia N in the paddy soils, are changed to nitrate when the soil is dried before puddling, because nitrate concentration is noted only in this period of the year. However, effluent loads were largest from the last days of the first period to second period, due to the very large drainage discharge during this period.<BR>In the case of P, the highest concentration and largest effluent loads were both found in the second period. The PO4-P concentrations were very low, so it seemed that almost all the P was absorbed by the soil particles in the drainage water. The high concentrations of P were made by the processes of paddling and transplanting, because the P concentration in the daytime were much higher than at night.<BR>The characteristics of the effluent loads of N and P differ greatly. As the effluent loads of N and P are affected by the drainage discharge, it is possible to reduce the effluent loads of N and P from paddy fields by correct irrigation water management.

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