K. Yokota - Academia.edu (original) (raw)

Papers by K. Yokota

Tropical Agriculture and Development Volume 62, Number 2, 2018

This study investigates the impact of agriculture on the water quality of the Cisadane River syst... more This study investigates the impact of agriculture on the water quality of the Cisadane River system in West Java, Indonesia by focusing on one stream flowing from an upland area through an intensive agricultural area before merging with the rest of the river system downstream. In total, 25 water samples were collected from this river system over a straight-line distance of ~70 km and an altitudinal difference of 750 m during the dry season of 2015 and the rainy season of 2016. The samples were analyzed to measure the pH, EC, and concentrations of NO3-N, NH4-N, and PO4-P. The average contamination in the water samples during the dry and rainy seasons was 0.61 and 0.45 mg NO3-N L-1, respectively, 0.56 and 0.28 mg NH4-N L-1, respectively, and 0.64 and 0.55 mg PO4-P L-1, respectively. The results revealed that water was contaminated by inorganic P even in the upper stream. Moreover, the spring water in the agriculture-intensive areas of a rural community, which is believed by the locals to be sufficiently clean for use, was found to more be contaminated by nitrogen than the water in the lower part of the river. As the flow of contaminated water can cause eutrophication in estuaries, it is important to characterize the contamination of water systems to encourage the implementation of sustainable water management strategies. Key words: Eutrophication, Fertilizer, Nitrogen, Phosphorus, Water quality

Tropical Agriculture and Development Volume 62, Number 2, 2018

This study investigates the impact of agriculture on the water quality of the Cisadane River syst... more This study investigates the impact of agriculture on the water quality of the Cisadane River system in West Java, Indonesia by focusing on one stream flowing from an upland area through an intensive agricultural area before merging with the rest of the river system downstream. In total, 25 water samples were collected from this river system over a straight-line distance of ~70 km and an altitudinal difference of 750 m during the dry season of 2015 and the rainy season of 2016. The samples were analyzed to measure the pH, EC, and concentrations of NO3-N, NH4-N, and PO4-P. The average contamination in the water samples during the dry and rainy seasons was 0.61 and 0.45 mg NO3-N L-1, respectively, 0.56 and 0.28 mg NH4-N L-1, respectively, and 0.64 and 0.55 mg PO4-P L-1, respectively. The results revealed that water was contaminated by inorganic P even in the upper stream. Moreover, the spring water in the agriculture-intensive areas of a rural community, which is believed by the locals to be sufficiently clean for use, was found to more be contaminated by nitrogen than the water in the lower part of the river. As the flow of contaminated water can cause eutrophication in estuaries, it is important to characterize the contamination of water systems to encourage the implementation of sustainable water management strategies. Key words: Eutrophication, Fertilizer, Nitrogen, Phosphorus, Water quality