关键词: 水稻土, 种植年限, pH, 土壤养分

Abstract: Based on the combined method of field investigation and indoor analysis, the status and variation of pH and nutrients in the surface soil of the paddy field （0~20 cm） under different cultivation years in the double cropping rice area in the south were investigated by Hunan province as an example. The results showed that the pH of the soil in the study area was 5.26~7.77, and most of them were weakly acidic to neutral soil. The content of soil organic matter reached the upper middle level, and there were great differences between different regions. On the whole, the soil organic matter in the paddy field reached the lowest value in 6 years, and rebounded in 8 years. The contents of organic matter, total nitrogen and available phosphorus in the topsoil were at the upper middle level, while the contents of alkali hydrolyzable nitrogen, available potassium, available iron, manganese, copper and zinc were at a higher level. Soil pH decreased with the increase of planting years. The content of soil available phosphorus decreased first and then increased. The content of soil available iron increased in 1~6 years, while the contents of soil total nitrogen, alkali hydrolyzable nitrogen, available potassium, available manganese, available copper and available zinc did not change significantly with the extension of planting years.

Key words: paddy soil, cultivating years, pH, soil nutrients