Search

The soil NO3− concentration and N2O emissions plays a crucial role in mitigating greenhouse gas emissions and minimizing greenhouse soil degradation concurrently. However, it is essential to understand the extent to which management practices and environmental factors influence the reduction in NO3− concentration and N2O emissions in greenhouse soils. Here, we conducted a meta-analysis, compiling a database of NO3− concentration and N2O emissions in response to either nitrogen or irrigation management in greenhouse vegetable-based systems in China. In summary, controlling the amount of total nitrogen application and irrigation water within specific ranges can effectively reduce both the greenhouse NO3− concentration and N2O emissions. Compared to chemical nitrogen management, the application of slow-release fertilizer could concurrently reduce the soil NO3− concentration and N2O emissions by 0.20 and 0.36 times, respectively. Positive relationships were observed between soil NO3− concentration and N2O emissions under conditions of higher soil organic carbon (OC), total nitrogen (TN), alkali-hydrolyzed nitrogen (AN), and pH, as well as a lower soil temperature (ST) and bulk weight (BW). Under conditions with a higher OC and pH, an appropriate nitrogen application rate is more effective in reducing N2O emissions. While increasing irrigation can reduce soil NO3− concentrations, it also raises the risk of significant NO3− leaching. Overall, nitrogen and irrigation management should be tailored to local soil physicochemical properties to concurrently regulate soil NO3− concentrations and N2O emissions in greenhouse environments. [ABSTRACT FROM AUTHOR]

This study was conducted to determine whether plants in the presence or absence of competition differ in their responses to warming, and whether density modifies the effect of warming. Picea purourea seedlings were grown under ambient and warming (ambient +2.2 °C) conditions in climate control chambers with two different planting densities. After 4 years, seedlings were harvested and measured for height, stem diameter, leaf area, structural biomass, carbon, nitrogen, chlorophyll and carbohydrate levels of needles, branches, stem and roots. At low density, warming increased height, stem diameter, total leaf area biomass production and carbohydrate concentration per seedling, while it decreased C/N ratio for all plant parts, but did not affect chlorophyll content. By contrast, at high density, although warming increased biomass and total leaf area, it did not affect plant height and stem diameter. At the same time, it had different effects on chlorophyll content, C/N ratio and carbohydrate levels among plant parts. On the other hand, high density limited plant growth and altered resource allocation pattern. Our study demonstrates that planting densities decreased the temperature-induced growth enhancement of P. purpurea seedlings and the effects of warming on resource allocation not only showed density-dependence, but also vary with tissue age classes and root diameter; the responses of plants to elevated temperature, acquired from plants growing as individuals, may not be applicable to plants grown under intraspecific competition as typically found in the field. [ABSTRACT FROM AUTHOR]

In a pot experiment, the aqueous extract of 10 years old Zanthoxylum bungeanum's leaves was used to water Z. bungeanum seedlings to test its effects on soil microbes and enzyme activities. The results showed that the leaf extract decreased the total amount of microbes and the quantity of bacteria, fungi and actinomyces in rhizosphere soil, but increased the total amount of microbes in non-rhizosphere soil. After watering with the extract, the proteinase, invertase and acid phosphatase activities in rhizosphere soil were considerably lower than those in nonrhizosphere soil, while catalase and polyphenol oxidase activities were in adverse. Soil proteinase activity had a significant positive correlation with invertase activity, but a significant negative correlation with actinomyces amount. Soil polyphenol oxidase activity had a significant negative correlation with invertase activity, but a positive correlation with the total amount of microbes and the quantity of bacteria, fungi and actinomyces. Soil actinomyces only had significant correlations with proteinase, polyphenol oxidase and invertase activities and fungi.

Pot experiment was carried out to study the effect of application bioorganic manure on soil nitrogen supplying characteristics. Compared with the application of raw rice straw, a combined application of bio-organic manure and inorganic nitrogen fertilizer could boost the content of microbial biomass carbon and nitrogen, and the increased percentage could be 300-400%. A strong immobilization of nitrogen by microorganisms was always followed by a net N mineralization, which was mostly favorable for the growth and development of plant, and improved the use efficiency of nitrogen fertilizer.