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Land use pattern, irrigation, and fertilization effects of rice-wheat rotation on water quality of ponds by using self-organizing map in agricultural watersheds

Li, Yufeng, Wright, Alan, Liu, Hongyu, Wang, Juan, Wang, Gang, Wu, Yuqing, Dai, Lingjun
Agriculture, ecosystems & environment 2019 v.272 pp. 155-164
agricultural land, agricultural watersheds, chlorophyll, irrigation, land use, pollution, ponds, rice, seasonal variation, surface area, uncertainty, water management, water quality, wheat
Revealing the relationship beween land use patterns and pond water quality is helpful to make water resource management decisions and improve agricultural pollution at the watershed scale. However, there is uncertainty about how irrigation and fertilization affect land use-water relationships. This study used a self-organizing map method to classify 51 created ponds and examined how land use pattern indices relateto pond water quality by identifying the variables in different clusters. The influence of irrigation and fertilization on water-land use associations were further explored. The self-organizing map classified ponds into five clusters, from least to most nutrient rich, with different variables of land use in clusters. Water quality improved as the percentage of pond surface area in the watershed increased, and decreased as farmland proportion increased. Land use patterns, such as patch density and ditch density, actually affected concentrations of chlorophyll a in pond water. Regardless of wheat or rice season, the weakening effects of fertilization and irrigation on land use-water relationships occurred among most ponds clusters. Irrigation and fertilization in the wheat season had more influence on water and land use relationships than in the rice season. Based on these results, water resource protection regulations should consider similar pond conditions within land use of watersheds to optimize mitigation strategies for different land-use characteristics and seasonal variation.