Organic fertilizers increase microbial community diversity and stability slowing down the transformation process of nutrient cycling.

Abstract

Background: Soil microbes play a central role in nutrient recycling in soils: however, the genetic mechanisms governing their responses to long-term fertilization remain poorly understood. While the agronomic benefits of long-term fertilization are well-documented, the genetic mechanisms and ecological processes underlying microbial community responses to different fertilization regimes remain poorly understood, particularly in unique soil systems such as black soils (Mollisols), which are critical for global food security. A deeper insight into how organic and inorganic fertilizers influence microbial assembly, functional potential, and community stability is essential for developing sustainable soil management practices.

Results: This study deciphers microbial assembly mechanisms, functional gene dynamics, and community restructuring in black soils subjected to 44 years of chemical fertilizer (CF), manure amendment (M), and integrated chemical fertilizer with manure (CFM) treatments. Results revealed that CF significantly enhances functional gene abundance related to carbon (C) degradation (e.g., starch, cellulose, chitin and lignin) and nitrification, accelerating the conversion of recalcitrant C to labile C pools and ammonium to nitrate. Conversely, M and CFM treatments promote microbial diversity and stability while decelerating nutrient transformation processes. In addition, microbial assembly mechanisms shift from stochastic to deterministic processes with long-term fertilizer application in CF. The structural equation modeling (SEM) indicated that soil chemical properties shape both the diversity and composition of taxonomic and functional gene communities which subsequently regulate microbial -mediated nutrient cycling processes and crop yield.

Conclusions: Our findings highlight the trade-offs between microbial functional potential and community stability under contrasting fertilization strategies, emphasizing the need to integrate microbial metrics into sustainable land management frameworks.