No abstract

Straw return is an important farmland management practice that influences the activity of soil nitrogen. Few studies have examined the distribution of soil nitrogen and its components in wheat–rice cropping fields in subtropical China. This study assesses the influence of different years of straw return on the distribution and variation of total soil nitrogen (TN), light fraction nitrogen (LFN), heavy fraction nitrogen (HFN), particulate nitrogen (PN), and mineral-bound nitrogen (MN). We conducted a field experiment with eight years of straw retention treatments in 2017 (no straw retention, NR; 1 year of straw retention, SR1; 2 years of straw retention, SR2; 3 years of straw retention, SR3; 4 years of straw retention, SR4; 5 years of straw retention, SR5; 6 years of straw retention, SR6; 7 years of straw retention, SR7) and one more treatment in 2018 (8 years of straw retention, SR8) in a rice–wheat cropping system at Yangzhou University Experimental Station in China. The results demonstrated that as the number of years of treatment increases, the content of TN, LFN, HFN, PN, and MN at each soil layer gradually increases. Compared with NR, the highest increase in TN, LFN, HFN, PN, and MN under SR1-SR8 in the 0–20 cm soils was 38.10%, 150.73%, 35.61%, 79.97%, and 27.71%, respectively, but increases in TN, HFN, and MN content gradually slowed after six years of straw return. The contents or variation of TN were extremely significantly correlated (p < 0.01) with that of LFN, HFN, PN, and MN, while LFN had the highest variation. In general, straw return could improve the quality of the 0–20 cm nitrogen pool. LFN was the best indicator of changes to the soil nitrogen pool affected by years of straw return.

Pollution from livestock and poultry is the main source of agricultural non-point-source pollution, which directly affects the rural ecological environment as well as the quality and safety of agricultural products. Based on eld experiment data of broiler farmers in China, this paper analyzes the cleaner production behavior of farmers from the perspective of incomplete contracts and social trust. We nd that social trust can promote farmers' cleaner production behaviors. Moreover, we nd that contract farming (CF) has a signi cant positive effect on farmers' social trust and cleaner production behaviors. Further analysis indicates that CF not only directly promotes farmers' cleaner production, but can also indirectly promote farmers' cleaner production by improving their interpersonal and institutional trust. Overall, this research offers a new point of view for improving the rural environment and sheds light upon how the government can formulate relevant policies to promote farmers' cleaner production technology adoption.