Optimizing effects of organic farming and moderately low nitrogen levels on soil carbon and nitrogen pools, humus composition and related enzyme activities

Abstract

With the development of intensive agriculture, soil health issues has received widespread attention. However, the mechanism of response to soil carbon and nitrogen pool sequestration characteristics under different cultivation practices in combination with nitrogen application is not yet elucidated. This limits the idea of trying to improve the soil biosystem in paddy fields through organic cultivation combined with appropriate nitrogen reduction fertilization. A split-plot design was employed, with cultivation methods (organic cultivation [OF] and conventional cultivation [CF]) and nitrogen levels (pure nitrogen at 180 kg·hm− 2 [N12] and pure nitrogen at 270 kg·hm− 2 [N18]) combined into four treatments. The impacts of organic and conventional cultivation as well as different nitrogen fertilizer application rates on soil properties were compared. The results demonstrated that organic cultivation combined with appropriate nitrogen reduction significantly increased the total carbon content of the surface soil and significantly increased the organic carbon content in the soil. Soil ammonium nitrogen content showed an overall trend of decreasing and then increasing, while the opposite was true for soil nitrate nitrogen content. Notably, the organic cultivation increased the activity of enzymes involved in the carbon and nitrogen cycle and the content of humic acid in the tillage layer, which led to the improvement of the soil aggregate structure.This research indicates that organic cultivation combined with appropriate nitrogen reduction fertilization positively affects soil carbon and nitrogen pool characteristics. This study provides new insights for restoring soil fertility and promoting sustainable agriculture.