Nitrate pollution in groundwater and strategies to reduce pollution

• Published in: Water science and technology 2002-01, Vol.45 (9), p.29-35
• Main Authors: SHRESTHA, R. K, LADHA, J. K
• Format: Article
• Language: English
• Subjects: Agriculture; Agronomy. Soil science and plant productions; Applied sciences; Biological and medical sciences; Capsicum annuum; Catch crops; Cereal crops; Corn; Cropping systems; Crops; Drinking water; Dry season; Earth sciences; Earth, ocean, space; Ecosystem; Engineering and environment geology. Geothermics; Environmental Monitoring; Exact sciences and technology; Fertilizers; Freshwater; Fundamental and applied biological sciences. Psychology; Groundwater; Groundwater pollution; Groundwaters; Hydroxyapatite; Indigo; Leaching; Natural water pollution; Nitrates; Nitrates - analysis; Nitrogen; Organizations; Oryza; Peppers; Philippines; Philippines, Ilocca Norte, Magnuang; Pollution; Pollution control; Pollution, environment geology; Profiles; Rain; Rainy season; Rice; Seasons; Soil; Soil and water pollution; Soil Pollutants - analysis; Soil profiles; Soil properties; Soil science; Soil water; Soil water movement; Transplantation; Tropical Climate; Vegetables; Water Movements; Water Pollutants - analysis; Water pollution; Water Pollution - prevention & control; Water Supply - standards; Water treatment and pollution; Watersheds; Wet season
• ISSN: 0273-1223; 1996-9732
• DOI: 10.2166/wst.2002.0197

The input-intensive rainfed tropical ecosystem, where wet season (WS) rice (Oriza sativa L.)-dry season (DS) diversified high-value upland crops like vegetables predominate, has resulted in a problem of a large leakage of N into the environment, thereby polluting the water. Excessive use of N fertilizer in high-value crops grown in DS is economically motivated. Out of twenty water sources evaluated in a watershed with a total area of 265 ha located in Magnuang, Ilocos Norte, Philippines, twelve had near or above the World Health Organization's (WHO) NO3-N limit for drinking water of 10 ppm. Soil mineral N (upper 100 cm) observed in seven rice-sweet pepper (Capsicum annuum L.) farmers' fields ranged from 111 to 694 kg ha(-1) which decreased by 10 to 68% in plots with dry-to-wet (DTW) crops like indigo, indigo+mungo and corn. In fallow plots where mineral N was either maintained or increased, it showed movement to lower soil profiles demonstrating NO3 leaching without a crop. On average, maize (Zea mays L.) captured 176 kg N ha(-1) and indigo (Indigofera tinctoria L.) 194 kg N ha(-1). In both fallow and planted plots, mineral N declined to low levels at 100% water-filled pore spaces (WFPS) before rice transplanting. A strategy for including indigo plus maize as a N-catch crop is proposed to decrease NO3 leaching and maximize N use efficiency in a rice-sweet pepper cropping system.