Abstract:

This study aims to clarify the response of organic carbon distribution in cotton soil aggregates to different continuous cropping years. Taking cotton field soil of 5, 12 and 17 years’ continuous cropping (L₅, L₁₂ and L₁₇) as the research objects, the soil aggregates’ distribution and organic carbon content were analyzed. The results showed that compared with that of the control (1 year cotton planting), the content of aggregates >2 mm decreased after continuous cropping for 17 years by 16.7% and 13.2% in 0-20 cm and 20-40 cm soil layer respectively. The content of soil organic carbon increased after continuous cropping for 5 years, which were the highest of 11.8 g/kg and 10.6 g/kg in 0-20 cm and 20-40 cm soil layer respectively, significantly increased by 16.2% and 15.1% compared with that of the control. The contribution rate of soil aggregates>2 mm to organic carbon was the highest, accounting for more than 50%, while the aggregates<0.053 mm had the lowest contribution rate. In conclusion, though continuous cropping was not conducive to the maintenance of soil quality, short-term continuous cropping was beneficial to the accumulation of soil organic carbon. In this experiment, the soil organic carbon content reached the maximum after 5 years of continuous cropping, and then decreased gradually.

Key words: cotton field, continuous cropping, soil aggregates, organic carbon, contribution rate, soil layer