Search

The application of slow-release nitrogen fertilizer not only economizes labor input, but also decreases the frequency of use of mechanical intakes, with significant implications in advancing modern intensive agricultural production. Whether slow-release nitrogen fertilizer application can influence the association between microbial diversity and soil multifunctionality remains controversial. This study analyzed the spatial variances of soil environmental factors, soil multifunctionality, and their correlations with bacterial and fungal communities under five nitrogen application rates. The key factors influencing the dominant microbial species and community structures at different spatial locations were determined by the slow-release nitrogen fertilizer application rate, and the driving factors and dominant species of soil multifunctionality were identified. In contrast to the control group, moderate slow-release nitrogen fertilizer application enhanced soil multifunctionality and ameliorated the resilience of microbial diversity loss at diverse spatial locations resulting from irrational nitrogen fertilizer application. The resilience of the fungal community to disturbances caused by fertilization was lower than that of the bacterial community. Bacterial diversity exhibited a significant correlation with soil multifunctionality, and the soil multifunctionality intensity under 240 kg ha−1 treatment increased by 159.01% compared to the CK. The main dominant bacterial communities and the dominant fungal community Ascomycota affected soil multifunctionality through slow-release nitrogen fertilizer application. Structural equation modeling and random forest analysis demonstrated that bacterial community diversity, particularly in bulk soil and the rhizosphere, community composition, and soil nitrogen form are the primary driving factors of soil multifunctionality. Results indicated that the microbial niche alterations induced by slow-release nitrogen fertilizer application positively affect soil multifunctionality.

The purpose of this study is to clarify the differential effects of the application rate of slow-release nitrogen fertilizer (SRFN) on the nitrogen (N) accumulation dynamics, nutrient organ N distribution and transportation, yield, and N utilization efficiency of maize harvested using grain-type machines. This has significant implications for the scientific application of SRFN, as well as for reducing its application rate and improving its efficiency, in the agro-pastoral transitional zone of northern China. In a long-term positioning experiment that began in 2018, five treatments consisting of different SRFN application rates were set up, namely, N120 (120 kg ha−1), N180 (180 kg ha−1), N240 (240 kg ha−1), N300 (300 kg ha−1), and N360 (360 kg ha−1), with no fertilization during the growth period used as control (CK) treatment. To explore the characteristics of nitrogen accumulation dynamics in maize populations and the main factors affecting maize yield formation under the different SRFN application rate treatments, this study adopted a combination of quantitative analyses and model fitting, including logistic models, principal component analysis, and structural equation modeling. The research results show that SRFN application increased the aboveground N accumulation of the maize population, and the fitting effect of the logistic models was significant. The maximum rate of N accumulation in both years showed a trend of first increasing and then decreasing with the increase in the SRFN application rate. Compared with CK, SRFN application reduced the proportion of N distribution in the nutrient organs during the R6 stage, and it increased the N transport from the nutrient organs to the grains after the VT-R1 stage. With the increase in the SRFN application rate, both the economic yield and biological yield showed a single peak curve change and were maximized in the N240 treatment. The economic yield reached 15,342.07 kg ha−1 in 2020 and 16,323.51 kg ha−1 in 2021, increasing by 36.2% and 61.7% compared with CK, respectively. The apparent N fertilizer recovery rate, N uptake efficiency, N agronomic efficiency, and N fertilizer partial productivity all gradually decreased with the increase in the SRFN application rate. In maize populations, an appropriate SRFN application rate can adjust the characteristic parameters during the aboveground N accumulation rapid growth period, increase the N accumulation amount in aboveground parts, promote the transport of N from nutrient organs to grains, and improve yield. An application of 180–240 kg ha−1 SRFN is recommended for maize cultivation in the agro-pastoral transitional zone of northern China, as it is beneficial for stabilizing and increasing maize yield, as well as reducing the rate and improving the efficiency of N fertilizer.

Enhancing crop nitrogen use efficiency (NUE) in agricultural sciences is a pivotal challenge, particularly for high-demand crops like potatoes (Solanum tuberosum L.), the world’s third most significant food crop. This study delves into the molecular responses of potatoes to low nitrogen (LN) stress, employing an integrative approach that combines transcriptomics and metabolomics to compare two cultivars with divergent NUE traits: XS6, known for its high NUE, and NS7, characterized by lower NUE. Our research unveils that XS6 exhibits higher chlorophyll and N content, increased tuber yield, and elevated N assimilation capacity under LN stress conditions compared to NS7. Through transcriptome analysis, we identified critical genes involved in C and N metabolism that had higher expression in XS6. A significant discovery was the high-affinity nitrate transporter 2.7 gene, which showed elevated expression in XS6, suggesting its key role in enhancing NUE. Metabolomics analysis further complemented these findings, revealing a sophisticated alteration of 1252 metabolites under LN stress, highlighting the dynamic interplay between carbon and N metabolism in coping with N scarcity. The integration of transcriptomic and metabolomic data underscored the crucial role of trehalose in mitigating N deficiency and enhancing NUE. This study provides novel insights into the molecular mechanisms governing NUE in potatoes, offering valuable perspectives for molecular breeding to enhance NUE in potatoes and potentially other crops.

Rotation fallow is an effective way to overcome the obstacles associated with continuous cropping, being beneficial for the growth and development of crops. Soil micro-organisms are closely related to soil fertility, plant productivity, soil pathogenic bacteria, and crop health in agricultural ecosystems. To explore the effects of different rotation fallow modes on the diversity and functions of the soil bacterial community, a study was conducted in an arid area in the western foothills of the Greater Khingan Mountains. Using spring wheat variety Longmai 36 as the research material, this study systematically analyzed the changes and functional differences in soil physicochemical and biological characteristics, as well as microbial communities (endosphere, rhizosphere, and bulk soil) in spring wheat fields under five rotation fallow modes: Wheat2016–Wheat2017–Wheat2018(WWW), Wheat2016–Rape2017–Fallow2018(WRF), Wheat2016–Potato2017–Fallow2018(WPF), Wheat2016–Fallow2017–Rape2018(WFR), and Wheat2016–Fallow2017–Potato2018 (WFP). The results indicate that, compared to WWW, the soil urease activity, microbial biomass nitrogen content, and microbial biomass phosphorus content were significantly increased in the WFP mode (p < 0.05). In particular, the soil moisture content, organic matter, and total potassium content were increased by 6.88%, 3.34%, and 25.57%, respectively. The Shannon index and chao1 index of bulk soil (BS) and rhizosphere (RS) bacteria were significantly higher than those of endosphere (ER) bacteria (p < 0.05). Both ecological niche and rotation fallow modes affected the relative abundance of dominant bacteria, and the relative abundance of beneficial bacteria, such as Bacteroidetes, Firmicutes, and Verrucomimicrobia, significantly increased in the rotation fallow modes. The complexity and stability of bacterial networks, and abundance of nitrogen-cycling-related functional taxa were significantly improved, while the abundance of pathogen-related functional taxa was significantly decreased. The differences in soil bacterial community structure were closely related to soil physicochemical properties. Compared to ER, BS and RS bacterial communities, which are more susceptible to soil physicochemical properties, and soil pH are key driving forces for bacterial community distribution. In summary, compared with continuous cropping, the rotation fallow mode is beneficial for conserving soil moisture and nutrients, stabilizing soil pH, (i.e., making the soil tend to be neutral), increasing the abundance of beneficial bacteria in the soil, enhancing the complexity and stability of microbial ecological networks, and increasing the abundance of nitrogen-cycling-related functional taxa, thus improving crop growth and development.

(Aims) To clarify the mechanisms though which dense planting could alleviate the negative effect of the reducing N rate on yield, (Methods) an experiment with four nitrogen levels—0 (N0), 120 (N1), 180 (N2) and 240 (N3) kg N ha−1—and three plant densities—180 (D1), 240 (D2) and 300 (D3) × 104 basic seedlings ha−1—was conducted. (Results) Increasing plant density decreased the root length, root volume, root surface area and root tips of individual plant while it enhanced the aforementioned root traits in population. The chlorophyll content, photosynthetic rate, stomatal conductance and transpiration rate of the individual plants were decreased with the increase in plant density and enhanced with the increase in N level. The increasing density and N application rate enhanced the leaf area index, photosynthetic high-efficiency leaf area and canopy photosynthetically active radiation of population. N accumulation per plant was decreased with increasing density and was enhanced with an increasing N application level. Within the same N level, the N accumulation in the population, N production efficiency and N recovery efficiency were consistently D3 > D2 > D1. A high N application rate with high density was not conducive to improving the NR (nitrate reductase), GS (glutamine synthetase) and GOGAT (glutamate synthase) activities. The yield could be maintained as stable or improved if decreasing by 60 kg N ha−1 with increasing 60 × 104 basic seedlings ha−1 within the range of N application in this experiment. (Conclusions) These results indicated that the yield of wheat could be improved with less N application by adjusting the compensatory effects from the plant density in populations.