No abstract

Straw incorporation increases the amount of nutrients in soil and has a significant impact on soil nitrogen and microbial communities. However, no study has quantified the amount of nitrogen released and taken up by straw during its decomposition after it is incorporated into soil in the field. In this study, a method for estimating the amounts of nitrogen released and taken up by field-incorporated straw was proposed based on 15N-labeled corn straw, and the relationships between nitrogen release and uptake amounts and the related microbes were established. The results showed that the amounts of nitrogen released by the straw at different incorporation depths were not significantly different. Among all the treatments, the straw placed 15 cm above the soil surface and the straw mulched on the soil surface had the highest nitrogen uptake, and the straw placed 15 cm above the soil surface had the lowest net nitrogen release. The relative abundances of Burkholderiales, Flavobacteriales, Pseudomonadales, and Sphingobacteriales were significantly positively correlated with the 15N abundance and the nitrogen release speed of the straw. The relative abundances of Rhizobiales and Sphingomonadales were significantly negatively correlated with the 15N abundance in straw and significantly positively correlated with the amount of straw nitrogen uptake.

Inappropriate farm management practices can lead to increased agricultural inputs and changes in atmospheric greenhouse gas (GHG) emissions, impacting climate change. This study assessed the potential of straw retention to mitigate the negative environmental impact of different cropping systems on the Songnen Plain using the life cycle assessment (LCA) method combined with field survey data. Straw retention (STR) and straw removal (STM) treatments were established in continuous corn (CC) and corn-soybean rotation (CS) systems in a split-plot experiment. The effects of straw retention on the carbon footprint (CF) of cropland under different cropping systems were compared. The CF under CC was 2434.0–2706.9 kg CO 2 ha -1 yr -1 , 49.3%–57.3% higher than that under CS. Nitrogen fertilizer produced the most CO 2 , accounting for 66.2%-80.4% of the CF. The carbon balances of the CC and CS systems with STR were positive, with annual carbon sequestrations of 9632.5 and 2715.9 kg CO 2 ha -1 yr -1 , respectively. The carbon balances of the CC and CS systems with STM was negative, with annual carbon sequestrations of -3589.2 and -3006.2 kg CO 2 ha -1 yr -1 , respectively. This study demonstrates that STR under CC cultivation is an environmentally friendly practice for agricultural production, can help achieve high-yield and low-carbon production in rainfed cropland, and can support the sustainable development of grain production in Northeast China.