In order to maintain high yields and protect the environment, the replacement of chemical fertilizers with organic ones has received increasing attention in recent years. A 2-year field experiment (2015–2016) was carried out to assess the effects of substituting equal amounts of mineral fertilizer with organic manure on the yield, dry matter (DM), and nitrogen (N) uptake of spring maize (Zea mays L.) and on the mineral N (N_min) distribution in the soil profile. The treatments included chemical fertilizer; different amounts of maize straw, cow manure, and chicken manure; and an unfertilized control (CK). Compared with the chemical fertilizer treatments, equal amounts of substitutions with cow manure or chicken manure increased production, and a 25% nutrient substitution resulted in the best yield increase. Straw return had no effect on maize production, and 100% straw return resulted in reduced production. The N accumulation and DM content both exhibited a slow-fast-slow growth trend throughout the various growth stages, and the average N uptake and DM accumulation in response to the treatments followed the order of chicken manure > cow manure > chemical fertilizer > straw return > CK. The N_min content in the profile not only increased as the N_min application rate increased but also showed greater increases at certain depths than at the surface, indicating that excessive N led to leaching. These results suggest that an appropriate proportion of organic substitution not only provides enough nutrients but also improves the soil environment and leads to increased yields. This technique represents a practical method of continuously increasing production and reducing the risk of N leaching.

Currently, the impact of changes in precipitation and increased nitrogen(N) deposition on ecosystems has become a global problem. In this study, we conducted a 8-year field experiment to evaluate the effects of interaction between N deposition and precipitation change on soil bacterial communities in a desert steppe using high-throughput sequencing technology. The results revealed that soil bacterial communities were sensitive to precipitation addition but were highly tolerant to precipitation reduction. Reduced precipitation enhanced the competitive interactions of soil bacteria and made the ecological network more stable. Nitrogen addition weakened the effect of water addition in terms of soil bacterial diversity and community stability, and did not have an interactive influence. Moreover, decreased precipitation and increased N deposition did not have a superimposed effect on soil bacterial communities in the desert steppe. Soil pH, moisture content, and NH₄⁺-N and total carbon were significantly related to the structure of bacterial communities in the desert steppe. Based on network analysis and relative abundance, we identified Actinobacteria, Proteobacteria, Acidobacteria and Cyanobacteria members as the most important keystone bacteria that responded to precipitation changes and N deposition in the soil of the desert steppe. In summary, we comprehensively analyzed the responses of the soil bacterial community to precipitation changes and N deposition in a desert steppe, which provides a model for studying the effects of ecological factors on bacterial communities worldwide.

Converting crop residues into biochar and subsequently incorporating it into soils is a promising strategy to improve carbon sequestration in agroecosystems. However, differences in the potential mechanisms for soil organic carbon (SOC) accumulation between biochar and its feedstock materials remain unclear. This study performed a nine-year field experiment involving four treatments in a Mollisol: mineral fertilizers alone and combined with maize straw or its biochar, and control without fertilizers and amendments. The main objectives of this study were to assess how straw and biochar incorporation influence SOC content, SOC chemical composition, microbial necromass carbon (MNC) content, and microbial community characteristics. Compared with mineral fertilizers alone, straw and biochar significantly (P < 0.05) increased SOC content, while biochar (40.5% increase) had more pronounced effects than straw (23.7% increase). Similarly, both straw and biochar increased MNC content and boosted microbial biomass, but straw had a more pronounced impact than did biochar. Additionally, biochar markedly increased SOC aromaticity by 26.6% (P < 0.05), while straw reduced SOC aromaticity by 2.85% (P > 0.05). Fungi, rather than bacteria, played a more crucial role in increasing SOC content through their necromass inputs under both straw and biochar incorporation. Our results demonstrated that straw enhanced SOC accumulation primarily through entombing effect of microbial necromass, while biochar enhanced SOC accumulation primarily through biochemical protection from recalcitrant aromatic carbon. The present findings provide valuable insight into the potential mechanisms of field practices that lead to maximize soil carbon sequestration. Graphical Abstract