Impact of agriculture on water pollution in Deli Serdang Regency, North Sumatra Province, Indonesia

The objective of this study was to assess the farming system of organic lowland paddy to water pollution compared with conventional farming system in Deli Serdang Regency. An environmental assessment in this research is limited to the water pollution caused by pesticides and chemical fertilizers. Water samples were analyzed, and the levels of nitrate and pesticides were taken of wetland and community wells. At the wetland, water samples were taken at the drains into the plot of rice field and the channel water out of the mapped fields. Water sampling was done every season and is upon subsequent fertilization. Each water composite was collected from ten sampling points which each consist of five sampling points of organic paddy farming system and five sampling points of conventional paddy farming system. The results showed that the level of pesticides in the drains coming out of paddy fields was higher than the levels of pesticides in the inlet and water in the community wells. The level of pesticides in organic cultivation was lower than conventional cultivation methods. In the dry season, the highest levels of nitrate obtained in the outflow water are significantly different, with inlet and well water, likewise the case with the rainy season. There was a tendency for increasing levels of nitrate in water, out water, and well water in the dry season compared to the rainy season.