Time in pasture rotation alters soil microbial community composition and function and increases carbon sequestration potential in a temperate agroecosystem

From forest to pastures and silvopastoral systems: Soil carbon and nitrogen stocks changes in northeast Amazônia

The Cerrado-Amazon ecotone has been under intense pressure over the years from agricultural and urban expansion, both of which are land uses that directly affect soil quality. The objective of this work was to evaluate the responses of soil carbon and nitrogen stocks, soil organic matter (SOM) quality, carbon isotopic composition (13C) from C3 and C4 plants and carbon sequestration and emission to silvopastoral systems, natural vegetation (NV), fallow pasture (FP), and intensive management pasture (IMP). Silvopastoral systems had different shading levels: 25 % (SP25), 50 % (SP50) and 75 % (SP75). The grass cultivated in all treatments was Megathyrsus maximus cv. Mombaça. The experimental design consisted of four replicates, and collection sites were distributed in strips throughout the study areas at different soil layers (0.00-0.05; 0.05-0.15; 0.15-0.30; 0.30-0.60 and 0.60-1.0 m deep). The conversion of natural vegetation in FP areas and silvopastoral systems (SP25 and SP75) led to increases in total C and N stocks (up to 1.0 m) when compared to other land use systems (SP50, IMP, and NV), which did not occur with total labile-C and C-POM. FP, SP25 and SP75 significantly increased labile C stocks in MAOM found in the 0.30-0.60 m layer. A greater enrichment of 13C in MAOM was observed with increasing depth for silvopastoral systems (SP25, SP50 and SP75) and NV. C-MAOM stocks derived from C3 plants were higher in soils under SP25 and SP75 and from C4 plants under FP. C-POM stocks were higher in all silvopastoral systems under study. IMP and FP affected δ13C values in MAOM and POM, especially in the 0.00-0.05 m layer. C sequestration increased under FP and SP25, with greater contributions from C4 and C3 plants, respectively. Of the silvopastoral systems, SP25 had the highest C stock in soil and contributed to the sequestration of 1.67 Mg C ha-1 yr-1.

Cultivated Land Use Zoning Based on Soil Function Evaluation from the Perspective of Black Soil Protection

Given that cultivated land serves as a strategic resource to ensure national food security, blind emphasis on improvement of food production capacity can lead to soil overutilization and impair other soil functions. Therefore, we took Heilongjiang province as an example to conduct a multi-functional evaluation of soil at the provincial scale. A combination of soil, climate, topography, land use, and remote sensing data were used to evaluate the functions of primary productivity, provision and cycling of nutrients, provision of functional and intrinsic biodiversity, water purification and regulation, and carbon sequestration and regulation of cultivated land in 2018. We designed a soil function discriminant matrix, constructed the supply-demand ratio, and evaluated the current status of supply and demand of soil functions. Soil functions demonstrated a distribution pattern of high grade in the northeast and low grade in the southwest, mostly in second-level areas. The actual supply of primary productivity functions in 71.32% of the region cannot meet the current needs of the population. The dominant function of soil in 34.89% of the area is water purification and regulation, and most of the cultivated land belongs to the functional balance region. The results presented herein provide a theoretical basis for optimization of land patterns and improvement of cultivated land use management on a large scale, and is of great significance to the sustainable use of black soil resources and improvement of comprehensive benefits.

Tillage activates iron to prevent soil organic carbon loss following forest conversion to cornfields in tropical acidic red soils

Previous studies have shown that deforestation and planting of corn resulted in the loss of soil organic carbon (SOC). However, this is not inevitable in regions with acidic red soil. We selected six cornfields that have been planted for 34 years and adjacent forest plots in southwest China. Using a structural equation model, we identified the SOC contents and 42 soil environmental factors in 11 soil layers that are conducive to SOC storage, and evaluated their relative weights hierarchically (0-40, 40-100, and 100-140 cm). Our results surprisingly indicated that after forest had been converted into cornfield, the SOC density did not change in any layer. In acidic red soil, reactive iron (Fe_o), soil water content, nitrogen, and pH were the main soil environmental factors that affected the storage of SOC. In the 0-40 cm soil layer, compared to forests, the contribution of Fe_o in cornfields increased significantly (by 11.65%), due to farming promoting the activation of iron, while the contribution of nitrogen decreased significantly (by 9.65%). In the 100-140 cm soil layer, the contribution of soil environmental factors was similar to that in the forest system, but the pH in cornfields increasing significantly (by 21.5%) may result from the leaching of hydrogen ions. Although the cultivation of cornfields caused a loss of nitrogen in the 0-40 cm soil layer, the increase in Fe_o promoted combination of iron and soil organic carbon, avoiding the soil layer from SOC loss.