Soil aggregate characteristics under different tillage and in-situ straw returning methods in western Jilin, China

Objectives In the quest for sustainable ways to mitigate the decline in soil structure caused by long-term intensive farming in the region and provide a theoretical basis for building a sustainable land-use, the effects of tillage patterns on soil quality indicators were studied by determining the changes in soil aggregate distribution and stability.

Methods A field trial was conducted in Ningjiang district of Songyuan City, western Jilin, China in October 2016. Treatments composed of tillage method and maize straw returning were arranged in randomized block design; conventional farming system involved continuous rotary tillage without straw returning (LR), continuous rotary tillage + straw returning (SR), plough and rotary tillage in turn + straw returning (STR), and plough and no-tillage in turn + straw returning (STN). In October 2018, the soil samples at 0–20 cm and 20–40 cm depth were collected, and the proportion of soil aggregates, the stability of aggregates and the content of organic carbon in aggregates were investigated.

Results Compared to LR treatment, straw returning significantly improved soil aggregate composition and stability (P < 0.05). Compared to SR treatment, the percentage of mechanically-stable aggregates with particle size > 0.25 mm was increased by 10.6% in STR and STN treatments. Compared with LR, geometric mean diameter (GMD) of STR and STN treatments was significantly increased, while the fractal dimension (D) decreased by 3.9% on average, and the unstable aggregate index (E_lt) also significantly decreased. STN treatment had higher soil organic carbon content in the surface layer (0–20 cm）than other treatments.

Conclusions Under the condition of straw returning, both the fields tilled using rotary-plough and no-tillage-plough have higher aggregate stability and corrosion resistance but smaller dimension. No-tillage-plough in turn method performs better than rotary-plough method in increasing the organic carbon content and the stability of soil aggregates. Plough and no-tillage in turn seems to be an effective measure for sustaining soil structure and fertility in the western part of Jilin Province, China.