Soil moisture, as an important variable affecting water–heat exchange between land and atmosphere, is an important feedback to climate change. Soil moisture is of great concern in Northern China, where arable land is extensive, but water resources are distributed unevenly and extremely sensitive to climate change. Using measured soil moisture data collected by the China Meteorological Administration from 164 stations during 1980–2021, we explored the drivers of soil moisture variation by analyzing its spatiotemporal variability using linear regression, partial correlation analysis, and geostatistical methods. The results indicated that (1) soil moisture increased from northwest to southeast in Northern China, with the lowest soil moisture in the IM; (2) the overall trend of soil moisture in most regions decreased, especially in the arid northwest and northeast China. However, soil moisture in some regions began to increase gradually in recent years, such as in northwestern Xinjiang and the central-eastern part of IM; and (3) soil moisture in the whole region was negatively correlated with temperature and sunshine duration and positively correlated with precipitation and relative humidity. The results of the study can provide valuable guidance for timely agricultural irrigation and the adjustment of cropping structures, thereby ensuring agricultural production and food security.

The subtropical region of East China is characterized by abundant water and temperature resources conducive to crop cultivation, and large areas of lowland have been widely used for agricultural planting. The objectives of the study were to explore feasible methods of greenhouse gas (GHG) reduction for rice–wheat rotation systems and to explain the mechanism underlying the effect of drainage on GHG reduction. Shallow ditch (SD) and deep ditch (DD) treatments in the wheat season were set up for drainage to control the paddy soil water content, with conventional non-ditching as the control group (CG). CH₄ and N₂O emission fluxes were continuously measured, and related soil physical and chemical properties were also measured in this study. The results showed that CH₄ emissions from paddy soil accounted for most of the global warming potential (GWP) in the rice–wheat rotation system. Drainage led to a significant reduction in cumulative soil CH₄ emissions during the rice and wheat seasons; however, the overall cumulative N₂O flux increased significantly. The total GWP produced by SD and DD in the three years was reduced by 58.21% and 54.87%, respectively. The GHG emission intensity (GHGI) of SD and DD declined by 60.13% and 56.40%, respectively. The CH₄ emission flux was significantly positively correlated with the 5 cm ground temperature but negatively correlated with the soil redox potential (soil Eh). The drainage decreased the soil water and soil organic matter contents and increased soil pH, which were the mechanisms that reduced the CH₄ emissions. The drainage increased the soil nitrogen content, which is the main reason for regulating N₂O. The findings indicate that SD and DD not only ensured a stable increase in production but also effectively reduced GHG emissions, and we recommend SD treatment for agricultural production.

To make full use of cornstalks from biomass waste, a green method for producing high value-added chemical products like organic acid with nickel oxide (NiO) as a solid oxidant was studied. The results show that the liquid product contains formic acid, lactic acid, pyruvic acid, oxalic acid and fumaric acid, etc. The yield of lactic acid was studied primarily. It was found that when the dosage of NiO is 3.5 mmol, the concentration of NaOH is 3 M, the reaction temperature is 230ºC and the reaction time is 3 hours, the yield of lactic reached 15.3%. In addition, the principles behind the conversion of cornstalks into organic acid with NiO was preliminary discussed. These results can offer a new method of developing a sustainable way for the efficient utilization of biomass waste.

Due to the overuse of fossil energy, fossil energy is facing exhaustion. Agricultural biomass such as wheat straw waste is a kind of clean energy which can replace fossil energy and has important scientific research value and broad application prospect. In this paper, wheat straw was used as raw materials, and the straw was converted into lactic acid, oxalic acid and fumaric acid under alkaline hydrothermal conditions. Improve the yield of organic acid by optimizing the reaction conditions such as NaOH concentration, reaction time and reaction temperature. The optimum reaction conditions were as follows: NaOH concentration 1.5 mol/L, reaction temperature 250ºC, reaction time 3 hours, total organic acid yield 13.5%, lactic acid yield 12.1%. The results can provide a new way for the green production of organic acids, and realize the efficient utilization of agricultural waste, reduce environmental pollution. At the same time, can produce good economic benefits, ecological benefits and social benefits.