논 토양에서 석탄회와 석고의 혼합제를 활용한 인산유출 저감

Abstract

Phosphorus transfer from agricultural soils to surface waters is an important environmental issue. Fly ash and phospho-gypsum which are industrial by-product were investigated as a means of reducing dissolved phosphorus in arable soil. To determine the optimum mixing ratio of fly ash (FA) and phospho-gypsum (PG) for reducing dissolved reactive P (DRP) in soil, various mixture ratio of FA and PG were mixed with two soil. The DRP content and pH in soils were analysed after 3 weeks incubation under flooding condition. Although DRP content in soils was significantly decreased by FA-PG mixture compared with control, there were no significant difference among the FA and PG mixture ratio of 75:25, 50:50, and 25:75. The mixture of 75% FA and 25% PG was selected for field test. A field experiment was carried out to evaluate the reducing DRP content in paddy soil to which 0 (NPK), 20 (FG 20), 40 (FG 40), and 60 (FG 60) Mg ha-1 of the mixture were applied. The DRP content was reduced by 31% at the application rate of 60 Mg ha-1. In contrast to deceasing DRP, Ca-P content increased significantly with the mixture application rate. After rice harvesting, available SiO2, P, and exchangeable Ca content in soil increased significantly with application rate due to high content of Si, P, and Ca in the mixture. Mixtures of fly ash and gypsum should reduce P loss from paddy soil and increase soil fertility.