Manure application decreases soil organic carbon priming by increasing mineral protection and nitrogen availability
Yalin Li, Lei Wu, Lingyun Tang, Fengling Ren, Xihe Wang, Zhu Ping, Nan Sun, Minggang Xu
Abstract
Rational chemical fertilizer application, especially combined with manure or straw amendment, serves as a key strategy for facilitating soil organic carbon (SOC) sequestration and soil fertility improvement. However, the effects of fertilization managements on the SOC priming induced by straw return remains unclear. Here, a microcosm was conducted to clarify the mechanisms of 13C-labeled maize straw addition effects on priming effect (PE) in two 29-year fertilized soils (Urumqi, UQ; Gongzhuling, GZL) subjected to four fertilization regimes (no fertilizer, CK; chemical fertilizers, NPK; combined application of NPK with straw, NPKS; combined application of NPK with manure, NPKM). Results showed that straw addition strongly increased native SOC decomposition by 15–44%, inducing positive PEs across sites and fertilization treatments. Compared to CK treatment, the NPK and NPKS treatments significantly increased PE by 26% and 98%, respectively, in the UQ soil, but had little effect on the PE in the GZL soil. The NPKM treatment strongly decreased PE by 51–55%, mainly due to the increased proportion of mineral-associated organic carbon (MAOC) and N availability, and decreased fungal abundances, as compared to the CK treatment in UQ and GZL soils. The PE intensities were significantly lower in GZL soil (5.1–11.7 mg CO2-C/g SOC) relative to UQ soil (13.7–54.8 mg CO2-C/g SOC), primarily due to the higher MAOC/SOC ratio and N availability in the former across fertilization regimes. Overall, manure application has the potential to mitigate soil C loss via priming, mainly resulting from enhanced SOC stabilization via mineral protection and increased N availability, thus facilitating SOC sequestration in agroecosystems.