Effects of multi-cropping systems on cinnamon soil aggregate stability, carbon and nitrogen distribution in western Henan Province

Objectives To address deterioration of soil structure and fertility caused by single long-term multi-cropping system of winter wheat-summer maize, alternative multi-cropping systems were tested for soil aggregate stability and nutrient availability in cinnamon soil of western Henan Province.

Methods A field experiment was carried out from 2014 to 2019. The tested annual rotation systems were winter wheat-summer maize (T1), winter wheat-summer peanut (T2), winter wheat-summer maize and peanut intercropping (2 rows of maize intercropping with 4 rows of peanut, T3). Soil samples at the 0–20 cm and 20–40 cm depths were collected after the harvest of summer crop in 2019, when there were total of 11 cropping. The composition and stability of soil aggregates, as well as the contents and distribution rates of organic carbon and total nitrogen in each particle size aggregate were analyzed by wet and dry sieving methods.

Results In the 0–20 cm soil layer, compared to T1 treatment, T2 and T3 treatments increased the > 0.25 mm mechanical aggregate (DR_0.25) by 5.9% and 9.9%, increased the > 0.25 mm water stable aggregate (WR_0.25) by 50.3% and 57.9%, decreased unstable soil aggregate index (E_LT) by 33.2% and 50.6%, decreased the percentage of aggregate destruction (PAD) of soil by 49.3% and 51.4%, increased the mean weight diameter (MWD) of soil aggregates by 36.4% and 47.0% and increased the geometric mean diameter (GMD) by 100.0% and 120.0% respectively. In the 20–40 cm soil layer, T2 and T3 treatments decreased the unstable soil aggregate index (E_LT) by 13.2% and 18.0%, decreased the percentage of aggregate destruction (PAD) of soil by 21.4% and 28.8%, increased the MWD of soil aggregates by 4.8% and 6.0% and increased the GMD by 11.5% and 7.7%, respectively, compared to T1 treatment. The contents of organic C and total N in 2–0.25 mm soil layer were the highest, and the contents of organic C and total N in 0–20 cm soil layer were higher than those in 20–40 cm soil layer. In the 0–20 cm soil layer, compared to T1 treatment, T3 treatment significantly increased the contribution rates of total N at all particle size aggregates and the contribution rate of organic carbon at >0.25 mm aggregate, profoundly decreased the contribution rate of organic C at <0.25 mm aggregate; T2 treatment also significantly increased the contribution rates of total N at 2–0.053 mm aggregates, and remarkably enhanced the contribution rate of organic C at >0.25 mm aggregate, but significantly decreased the contribution rate of organic C at 0.25–0.053 mm aggregate. Compared to T1 treatment, T2 and T3 treatments increased the contents of total organic C, total N, available P and readily available K, but the bulk density and pH had no significant difference among the three treatments in both 0–20 and 20–40 cm soil layers.

Conclusions Compare to traditional winter wheat-summer maize cropping system, the winter wheat-summer peanut, winter wheat-summer maize and peanut intercropping have immense advantages in terms of increasing the content of soil macro-aggregates, enhancing the mechanical stability and water stability of soil aggregates, improving the accumulation of organic C and total N in soil aggregates (especially >0.25 mm aggregates), and increasing the content of available P and readily available K in soil, which are beneficial to maintain the soil fertility and the long-term health of the cinnamon soil in western Henan Province. And the effect of winter wheat-summer peanut cropping system is better than that of winter wheat-summer maize and peanut intercropping system.