Soil's physical and chemical properties have greatly changed the soil nutrient with the increasingly severe global warming in recent years. As the largest grain reserve base in China, the farmland black soil in Northeast China can depend mainly on climate warming. The increase in winter temperature can lead to some change in the soil moisture, the number of freeze-thaw cycles, snow depth, and freezing depth, particularly in the accumulation and release of soil available nitrogen and phosphorus. The purpose of this study is to clarify the response of nitrogen and phosphorus in the black soil of farmland in Northeast China to global warming. A total of 12 plots were divided in the field test, where 6 plots were subject to the treatment of temperature increasing, and 6 plots were the control treatment. Two types of treatments were used for the field in situ experiments. The infrared radiation warming technology was used to simulate climate warming. Field experiments were then conducted to measure the soil environmental factors, including the concentration of ammonium nitrogen, nitrate nitrogen, total nitrogen, microbial biomass nitrogen, available phosphorus, and total phosphorus during the 6-month experimental period. A systematic analysis was made to explore the impact of temperature rise on the availability of nitrogen and phosphorus in the black soil of farmland. The results showed that the heating treatment significantly increased the soil temperature, soil humidity, and the number of freeze-thaw cycles. At the same time, the heating treatment with no snow cover on the soil surface delayed the freezing time, and then advanced the melting time, compared with the control. In addition, the heating treatment significantly reduced the concentration of ammonium nitrogen, nitrate nitrogen, total nitrogen, microbial biomass nitrogen, and total phosphorus, whereas, the content of soil available phosphorus significantly increased by 25.54 % (P <0.05). There was a decrease in the ratio of the soil's available nitrogen and phosphorus, while the ratio of the total nitrogen and phosphorus in the soil under the warming group. Compared with the control, the soil available nitrogen: available phosphorus ratio, and the soil total nitrogen: total phosphorus ratio decreased by 331.82% and 41.05%, respectively (P<0.05). Moreover, there was no same correlation between soil available nitrogen and available phosphorus with the environmental factors. A positive correlation was found between the soil's available nitrogen, soil temperature, and the number of freeze-thaw cycles, while there was a significant correlation between the available phosphorus, soil humidity, and freezing depth. The increasing soil temperature at various stages posed a significant impact on the soil's available nutrients during winter warming. Therefore, there was a significant loss of soil available nitrogen during thawing. A significant increase was found in the soil phosphorus, leading to the eutrophication of water bodies and the pollution of groundwater. Winter warming shared a profound impact on the effective terms of soil nitrogen and phosphorus. The heating treatment can be expected to alleviate the coupling effect of soil nitrogen and phosphorus. Particularly, the negative impact was previously found in the coupling mechanism between nitrogen and phosphorus on the ecosystem in Northeast China. The finding can provide a theoretical basis for efficient fertilization and the rational regulation of ecosystems for the better overall quality of farmland black soil in Northeast China in the context of future global warming.

This study aims to explore the effects of the fertilization strategies on the soil N₂O emission and nitrogen use of greenhouse tomatoes. A reasonable fertilization model was proposed to reduce the soil emission for the high yield of tomatoes in a greenhouse. A field trial was also conducted at the A-Cheng Experimental Research Base of the Northeast Agricultural University, Heilongjiang Province, China in 2023. Among them, the soil N₂O emission was monitored using a static box-gas chromatography. A systematic analysis was made to explore the patterns of soil nutrient contents, crop yield and nitrogen utilization efficiency. The soil N₂O emission and nitrogen use of tomato were then determined under different fertilizer treatments. A series of experiments were carried out on two types of fertilizers (compound and microbial fertilizers) and three nitrogen dosages (0, 120 and 180 kg/hm²). Five treatments were set as CK (no fertilizer), CF (constant compound fertilizer), RCF (reduced compound fertilizer), OF (constant microbial fertilizer), and ROF (reduced microbial fertilizer). The results showed that: 1) The total N₂O emission of microbial fungal fertilizer was reduced by 51.94% and 71.45% under the macronutrient and reduced nitrogen application, respectively, while the N₂O emission per unit of yield was reduced by 27.11%-47.75% (P<0.05), compared with the compound fertilizer. 2) The application of bacterial fertilizer increased the soil pH from 5.58 to 6.03, compared with the soil base value. There was the great potential to the soil acidification. Mycorrhizal manure was elevated the MBC and MBN, which increased by 20.47%-80.08% and 8.84%-59.15%, respectively, compared with the compound fertilizer. As the experimental period progressed, the total nitrogen content of the fungal fertilizer showed a continuous upward trend, and then increased under normoxic and reduced conditions, respectively, compared with the compound fertilizer. 3) The fungal fertilizer increased the tomato yield by 9.09%-13.68%, the agronomic efficiency of nitrogen fertilizer was improved by 25.85%-56.21%, and the nitrogen fertilizer utilization by 12.19%-17.99%, compared with the compound chemical fertilizer treatment under equal nitrogen. In conclusion, the reduced application of microbial fertilizers can be expected to serve as a promising fertilization strategy for less nitrogen losses and high yields of greenhouse tomatoes. Some recommendations can be given in greenhouse tomato systems for the green and sustainable production.