Subsurface manure application enhances soil quality, ecosystem multifunctionality, and crop yield in the North China Plain

Subsurface manure application has been suggested as a priming strategy to improve soil fertility and potentially enhance crop yield quickly. However, the soil quality and ecosystem multifunctionality responses and their relationship with crop yield remain uncertain. Here, a two-year field experiment was conducted to investigate the effects of different subsurface manure application methods (1T, one-time fertilization; and 2T, two-time split fertilization during two consecutive years) with the same manure amount on soil quality index (SQI), ecosystem multifunctionality (EMF), and crop yield in the North China Plain. Compared to control (no manure application, CK), 1T increased SQI at both 0-20 and 20-40 cm soil layers by 15-19 % in the first year, but no change in the second year. As a comparison, 2T increased SQI at 0-20 and 20-40 cm soils by 37-42 % compared to CK in the second year. Meanwhile, 2T increased soil EMF at 0-20 cm (0.4 unit) compared to CK over the two years. Both 1T and 2T increased soil EMF at 20-40 cm (0.1-0.8 unit) over the two years. The crop yield was positively related to surface SQI and subsurface EMF regardless of manure application method. Soil organic C, total C, total N, total P, and the C and P cycling-related enzyme activities were key factors that contributed to the improvement of SQI and EMF. The partial least squares path models revealed that the two subsurface manure application methods enhanced surface SQI and subsurface EMF by improving topsoil nutrients and subsoil enzyme activities separately, consequently increasing crop yield. Overall, our results documented that subsurface manure application is an effective strategy for improving soil quality and crop yield.