Methane consumption by soils of dryland rice agriculture: influence of varieties and N-fertilization

Maize/peanut rotation intercropping improves ecosystem carbon budget and economic benefits in the dry farming regions of China

Monoculture is widely practiced to increase crop productivity, but long-term adaptation has drawbacks as it increases the depletion of soil nutrients and reduces soil quality, especially in dryland areas. Conversion from traditional maize monoculture to intercropping improves sustainable production. However, maize/peanut intercropping, especially rotation of planting strips impacts of maize/peanut intercropping in dryland on carbon (C) budgets and economic benefits remain unclear. In this study, a 5-year field experiment was conducted to evaluate the influence of maize/peanut intercropping with rotation of planting strips on soil health, indirect CO2-eq greenhouse gas emissions, and ecosystem C inputs. Four intercropping treatments viz. maize monoculture, peanut monoculture, maize/peanut intercropping, and maize/peanut rotation-intercropping were tested from 2018 to 2022. Maize/peanut rotation intercropping significantly improved the land equivalent ratio followed by intercropping and monoculture. Rotation-intercropping also improved economic benefits over intercropping and monoculture which were mainly associated with increased peanut yield where the border rows contributed the maximum, followed by the middle rows. Moreover, rotation-intercropping significantly increased the soil organic C and nitrogen (N) content. Rotation-intercropping decreased indirect CO2-eq greenhouse gas emissions and ecosystem C inputs by 3.11% and 18.04%, whereas increased ecosystem C outputs and net ecosystem C budget by 10.38% and 29.14%, respectively, over the average of monoculture. On average for intercropping and monoculture, rotation-intercropping increased ecosystem C emission efficiency for economic benefits by 51.94% and 227.27% in 2021 and 2022, respectively, showing the highest C utilization efficiency than other treatments. In the long run, maize/peanut rotation-intercropping can be practiced in dryland agriculture to achieve sustainable agriculture goals.

Biochar application significantly affects the N pool and microbial community structure in purple and paddy soils

BACKGROUND

The increasing demand for food production has resulted in the use of large quantities of chemical fertilizers. This has created major environmental problems, such as increased ammonia volatilization, N2O emission, and nitrogen (N) leaching from agricultural soil. In particular, the utilization rate of N fertilizer is low in subtropical southern parts of China due to high rainfall. This causes not only large financial losses in agriculture, but also serious environmental pollution.

METHODS

In this study, 16S rDNA-based analysis and static-chamber gas chromatography were used to elucidate the effects of continuous straw biochar application on the N pool and bacteria environment in two typical soil types, purple and paddy soils, in southern China.

RESULTS

Straw biochar application (1) improved the soil N pool in both rhizosphere and non-rhizosphere soils; (2) significantly reduced the emission of N2O, with no difference in emission between 1 and 2 years of application; (3) increased the abundance of N-processing bacteria in the soil and altered the bacterial community structure; and (4) improved the tobacco yield and N use efficiency in paddy soil. These findings suggest that, in southern China, the application of straw biochar can promote N transformation in purple and paddy soils and reduce the emission of the greenhouse gas N2O.

Biochar application on paddy and purple soils in southern China: soil carbon and biotic activity

Soil carbon reserves are the largest terrestrial carbon pools. Common agricultural practices, such as high fertilization rates and intensive crop rotation, have led to global-scale environmental changes, including decreased soil organic matter, lower carbon/nitrogen ratios and disruption of soil carbon pools. These changes have resulted in a decrease in soil microbial activity, severe reduction in soil fertility and transformation of soil nutrients, thereby causing soil nutrient imbalance, which seriously affects crop production. In this study, 16S rDNA-based analysis and static chamber-gas chromatography were used to elucidate the effects of continuous application of straw biochar on soil carbon pools and the soil microbial environments of two typical soil types (purple and paddy soils) in southern China. Application of biochar (1) improved the soil carbon pool and its activity, (2) significantly promoted the release of soil CO2 and (3) improved the soil carbon environment. Soil carbon content was closely correlated with the abundance of organisms belonging to two orders, Lactobacillales and Bacteroidales, and, more specifically, to the genus Lactococcus. These results suggest that biochar affects the soil carbon environment and soil microorganism abundance, which in turn may improve the soil carbon pool.