Reduced water and nitrogen inputs boost microbial necromass carbon contributions to greenhouse soil organic carbon

Abstract

Soil microbial necromass carbon (MNC) plays a crucial role in the persistent soil organic carbon (SOC) pool. However, the impact of long-term different water-nitrogen managements on the soil MNC in the greenhouse vegetable production (GVP) remains unclear. Using a 12-year field experiment, coupled with soil physicochemical properties, C- and nitrogen (N)-related enzymatic kinetics and microbial communities’ measurements, the impact of six different water-nitrogen managements on MNC accumulation was examined. Our study showed that MNC constituted 47.7%–71.3% of SOC, with fungal necromass carbon (FNC) contributing 4.2-fold more than bacterial necromass carbon (BNC) on average. Compared to the high irrigation and chemical nitrogen fertilizer practices, water-saving practices under the high fertilization scenario increased BNC/SOC by 18.6% after the 12-year field manipulation. The reduced water-N treatments had the highest MNC/SOC proportions with an average of >60%, which was mainlyattributed to the increased FNC/SOC. The relative importance partitioningresults showed that root biomass, N-acetylglucosaminidase and C-cellobiohydrolase enzyme kinetics were the most important regulators of FNC/SOC, BNC/SOC and MNC/SOC, respectively. The partial least squares path modeling further revealed that soil substrates (e.g., root biomass and dissolved organic carbon) directly promoted FNC/SOC while suppressing BNC/SOC, whereas microbial communities enhanced both fractions. Hence, our study highlights the divergent response of FNC and BNC to the long-term water-nitrogen management in GVP. Therefore, optimized water-nitrogen management sustains crop productivity while enhancing MNC accumulation, thereby promoting SOC persistence and advancing green sustainable development of GVP.

Graphical abstract

Keywords

microbial necromass carbon / field experiment / greenhouse vegetation production / persistent soil organic carbon / water-nitrogen management

Highlight

	● Using 12-year water-nitrogen management soils, the MNC accumulation was investigated.
	● Contributions of FNC and BNC to SOC show divergent responses to water-nitrogen practices.
	● Reduced water-nitrogen input enhances MNC/SOC, primarily driven by FNC.
	● Reduced water-nitrogen practices benefit SOC persistence and the GVP’s sustainability.

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