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Phosphorus (P) fertilizer has been widely applied to improve crop yields in the North China Plain; however, most of applied P fertilizer is disabled due to the strong sorption/fixing processes in the soil. This study evaluates the change characteristics of soil properties on different textural soils and their relationships with the P adsorption and desorption under long-term fertilization to do a favor to make strategies for improving the P availability of the soil. Five textural fluvo-aquic soils including gritty sand, silt sand, sandy loam, medium loam, and light clay were investigated in a 27-year (1990–2017) long-term fertilization experiment at Zhengzhou (Henan province) of China. Soil samples were collected in 1990, 1999, and 2017 at 0–20 cm to measure soil properties (i.e., soil mechanical composition) and P adsorption and desorption characteristics. The clay and silt contents decreased and sand content increased in the light clay soil with the cultivation years, the opposite situation for the gritty sand and silt sand soils. The contents of total P, Olsen–P, and organic matter (SOM) in the five textural soils were increased over time. There were stronger P absorption capacity and weaker desorption ability for the light clay soil relative to others, which was reflected in the largest P maximum buffer capacity (MBC) and the lowest β value; however, the P adsorption capacity tended to decrease over time for the light clay soil. Clay and silt fractions were positively correlated with MBC, while negatively correlated with β (P

Nutrient availability and plant diversity are two important factors determining crop productivity in agricultural ecosystems, but little is known about the underlying mechanisms shaping microbial communities and their regulatory roles in soil biological activity and function. Here, we explored the impacts of fertilization regimes and crop rotations on soil physicochemical properties, crop yield and bacterial and fungal community structures in a 26-year field experiment. The critical determinants for regulating soil enzyme activity profiles involved in carbon (C), nitrogen (N) and phosphorus (P) cycling were identified by the partial least squares path model (PLS-PM). Long-term inorganic or organic fertilization significantly increased soil total N by 27%–77% and crop yield by 237%–419% and decreased soil pH by an average of 0.4 units when compared with non-fertilized control. Soil bacteria were more sensitive than fungi to the fertilization practices. Nutrient additions enriched copiotrophic taxa affiliated to the Pseudomonadaceae and Cytophagaceae bacterial families, but reduced some Acidobacteria such as subgroup 4 RB41, which was the most sensitive biomarker responding to no fertilization. Conversely, fungi were more active in response to crop conversion from wheat-maize to wheat-soybean rotation, leading to a 3-fold enhancement of an unclassified Sordariomycetes family in soybean-based rotation. PLS-PM revealed that fertilization-induced increases in soil enzyme activities were regulated by the bacterial community, while plant-driven alterations in yield, organic C input and soil aggregate-size distribution played an important role for fungal development, which, however, had no significant link to soil enzyme activity profiles. Our results suggest that different response patterns of soil bacteria and fungi to agricultural practices might have consequences for ecosystem function.

Crop nitrogen nutrition is an important indicator for evaluating crop growth. Rapid and non-destructive estimation of nitrogen accumulation in wheat leaves is of great significance for crop nitrogen fertilizer management. Based on field test data from multiple wheat varieties for different locations, years, nitrogen levels, and growth periods, the relationship between 11 canopy hyperspectral parameters and nitrogen accumulation in wheat plants was studied. According to the results of correlation and regression analysis, the flowering period of wheat was selected as the most suitable growth period for crop growth evaluation (the average R2 was 0.732, and the root mean square error (RMSE) was 0.354). A new vegetation index, NDchI*DDN (referred to as the nitrogen accumulation vegetation index, abbreviated as NAVI), was constructed based on the pairwise combination of traditional vegetation index products. This parameter had a high correlation with plant nitrogen accumulation (R2 = 0.856), and the root mean square error (RMSE) was 0.296. Tested by independent experimental data, the fitting degree of the plant nitrogen accumulation inversion model established with NAVI as the variable was R2 = 0.861, the relative error RE = 9.3%, RMSE = 0.398, and the prediction accuracy was significantly higher than other models. Therefore, construction of a NAVI-based plant nitrogen accumulation monitoring model gave ideal test results, which could reduce the limitations of experimental conditions and is expected to provide new important technical support for precise fertilization.

The carbon sequestration potential is affected by cropping system and management practices, but soil organic carbon (SOC) sequestration potential under fertilizations remains unclear in north China. This study examined SOC change, total C input to soil and, via integration of these estimates over years, carbon sequestration efficiency (CSE, the ratio of SOC change over C input) under no fertilization (control), chemical nitrogen fertilizer alone (N) or combined with phosphorus and potassium fertilizers (NP, NK, PK and NPK), or chemical fertilizers combined with low or high (1.5×) manure input (NPKM and 1.5NPKM).; Results: Results showed that, as compared with the initial condition, SOC content increased by 0.03, 0.06, 0.05, 0.09, 0.16, 0.26, 0.47 and 0.68 Mg C ha-1 year-1 under control, N, NK, PK, NP, NPK, NPKM and 1.5NPKM treatments respectively. Correspondingly, the C inputs of wheat and maize were 1.24, 1.34, 1.55, 1.33, 2.72, 2.96, 2.97 and 3.15 Mg ha-1 year-1 respectively. The long-term fertilization-induced CSE showed that about 11% of the gross C input was transformed into SOC pool.; Conclusion: Overall, this study demonstrated that decade-long manure input combined with chemical fertilizers can maintain high crop yield and lead to SOC sequestration in north China. © 2016 Society of Chemical Industry.; © 2016 Society of Chemical Industry.

To estimate the leaf area index (LAI) in large areas, this paper analyzes the relationships between normalized difference vegetation index (NDVI) and the grassland LAI based on MODIS data in the southern grassy mountains and slopes of China. By using nonlinear fitting equation we constructed the basic estimation model of grassland LAI with NDVI as the independent variable and introduced precipitation and temperature as regulatory factors. The model was validated with observed data in different years and the results showed that there was a good correlation between the simulated and observed LAI value with a statistically significant level of R2. RMSE was 0.302 and RRMSE was 0.154. It was also found that the spatial distribution of grassland LAI in south China showed a remarkable zonal characterization, and temporal distribution showed a single peak curve. These results provided a theoretical basis for the effective management of southern grassland resources and the carbon sink estimation of the nationwide grasslands.