Abstract:

To investigate the effects of the new triple-cropping rotation model of rapeseed-rice-bean on soil physicochemical properties and rice trace element content, and to promote the improvement and standardization of cultivation techniques for this rotation model, a field positioning experiment was conducted. Field positioning experiment was conducted with two treatments: continuous early rice-late rice cropping and rapeseed-rice-bean rotation, analyzing the effects of different treatments on basic soil physicochemical properties and rice trace element content. The results showed that, compared with traditional continuous cropping, the soil pH value significantly decreased after two years of rapeseed-rice-bean rotation, alkali-hydrolyzable nitrogen and available potassium content increased significantly,but no significant difference was observed in cation exchange capacity, bulk density and organic matter, total nitrogen, total phosphorus, total potassium and available phosphorus content. After two years of rapeseed-rice-bean rotation, the soil alkali-hydrolyzable nitrogen and available potassium content significantly increased, and available phosphorus content increased, but the difference was not significant. After two years of rapeseed-rice-bean rotation, the total content of soil iron, manganese, zinc, copper, and cadmium showed no significant difference, but the available content significantly increased. After two years of rapeseed-rice-bean rotation, the cadmium content in the above-ground straw and brown rice of early rice significantly increased. Under the conditions of this experiment, rapeseed-rice-bean rotation can effectively improve the level of soil available nutrients, but it also significantly reduces soil pH value content, and poses a risk of heavy metal cadmium pollution in early rice.

Key words: rapeseed-rice-bean rotation, soil, physicochemical properties, available nutrients, trace elements