Aflizar, Husnain, Darmawan, Hermansah, T. Wakatsuki, S. Kuniaki and T. Masunaga
Phosphorus, Nitrogen and Potassium are important parameters for assessing soil fertility and water quality. However, study of NPK in soil has been concerned on fertilizer management to increase rice production. In the field, blooming of aquatic plants has been recently observed in the Singkarak Lake at the outlet of the watershed, which might indicate nutrient accumulation in the water body. Darmawan et al (2006) reported an increase of approximately 87% - 98% availabley phosphorus in soil of sawah due to phosphate fertilization during the 3 decades which has led to the growth of aquatic plants in downstream. However, information on the availability of N, P and K on rice production are lacking In the present study, we conducted a study on the distribution of NPK in relation to land use types and soil erosion status in Sumani watershed for better nutrient management in West Sumatra, Indonesia. We have already found that severe erosion occurred in upland of the watershed because of the land use change from forest to agricultural field. We expected that these factors might influence on NPK distribution in the watershed. Soil erosion is generally considered as prime cause for soil degradation. However, it may contribute to replenish nutrients in sawah and to increase nutrient load in downstream water, especially in lowland through deposition of fine soil particle eroded from the upland.
Keywords: Available P, Total N, Exchangeable K, Eutrophication, Indonesia, Soil erosion
Paper published inProceedings of the 10th International Conference of The East and Southeast Asia Federation of Soil Science Societies