Mixed sowing of Feed rape and Vicia villosa can substitute nitrogen fertilizer to improve soil multifunctionality in the Hetao irrigation District

Abstract

Soil multifunctionality (SMF) and crop production of continuous green manure returning is crucial for sustainable agricultural development. Multiple cropping of green manure after wheat harvest is a typical planting pattern in the Hetao Irrigation District, and maybe substitute nitrogen (N) fertilizer. However, information is scarce about how the green manure affected SMF and crop production under limited nitrogen inputs. A 7-year field experiment was conducted to investigate the effects of green manure types (Feed rape (FR), Vicia villosa (VV), Feed rape, and Vicia villosa mixed sowing (FR + VV)) on soil properties, enzyme activities, SMF, and rotated wheat yield under different N application rates (150 kg N ha−1, N150; no nitrogen, N0). The results showed that FR and FR + VV increased soil active carbon (C) and N fractions by 4.0 %-499.3 % and 11.3 %-147.8 % compared to VV, respectively. Enzyme activities with FR + VV were significantly increased by 13.7 %-82.9 % compared to FR and VV. SMF and CCI (carbon cycling index) were significantly affected by N fertilizer and green manure types, with N0 higher than N150 by two times and FR + VV higher than FR by 1.4–4.3 times and VV by 1.0–6.6 times in 0–20 cm soil layer. Spring wheat yield was significantly affected by N fertilizer and green manure types, with N0 significantly higher than N150 by 5.8 % and FR and FR + VV higher than VV by 8.0 % and 12.5 % under N150, respectively. Partial least squares path model detected that returning of multiple green manure had a significant positive and indirect effect on SMF through enhancing soil enzyme activities, and ultimately contribute to the improvement in wheat yield. In conclusion, the mixed sowing of FR and VV increased soil active C and N fractions and associated enzyme activities, and has the potential to improve the SMF and rotated wheat yield, thereby providing an effective approach to reduce N fertilizer.