关键词: 甜瓜, 土壤湿度, 减氮, 菌渣, 土壤酶, 营养, 微生物

Abstract: To investigate the effects of nitrogen reduction combined with mushroom substrates application on the growth characteristics，fruit quality，nutrient absorption，and soil microbial environment of sweet melon under different soil humidities，the thin‑skinned sweet melon Super Sweet White Phoenix was selected as the test object.Four nitrogen reduction+mushroom substrates treatment levels were set at two soil humidities（60%，90% soil moisture content），including conventional nitrogen application of 210 kg/ha（N₁₀₀），nitrogen reduction of 50%（N₅₀），nitrogen reduction of 50%+500 kg/ha mushroom substrates（N₅₀+SMS₁），and nitrogen reduction of 50%+1 000 kg/ha mushroom substrates（N₅₀+SMS₂），for a total of eight treatments. The results showed that with the increase of soil moisture content，the growth characteristics and fruit quality of melon showed an overall increasing trend. Under the same soil moisture conditions，compared with N100，sweet melons treated with N₅₀+SMS₂ had the highest plant height，stem thickness，and leaf area during the flowering and fruit setting stage and fruit enlargement stage. The soluble total sugar，vitamin C，soluble protein，and soluble solids content in sweet melon fruits increased by 29.6%—36.2%，9.3%—10.8%，11.3%—12.4%，and 13.7%—14.3%，respectively.The nitrogen，phosphorus，and potassium content in sweet melon stems and leaves also significantly increased，and the yield of sweet melons treated with N50+SMS2 under 90% soil moisture content was as high as 15.46 t/ha. In addition，the activities of sucrase，urease，and polyphenol oxidase in different soil layers of sweet melon soil showed a trend of 20—40 cm>0—20 cm. Nitrogen reduction combined with mushroom substrates could increase the activities of sucrase，urease，polyphenol oxidase，and catalase to varying degrees at different soil depths. Compared with N₁₀₀，the microbial biomass carbon（MBC）and microbial biomass nitrogen（MBN）in various soil layers treated with N50+SMS2 increased by 38.6%—79.2% and 56.5%—76.9%，respectively，while MBC/MBN showed no significant change. Soil soluble carbon（DOC） and soluble nitrogen（DON） increased by 52.8%—57.7% and 43.0%—81.5%，respectively，while DOC/DON also showed no significant change.The conclusion is that N₅₀+SMS₂ treatment under different soil moisture can effectively improve the soil environment，enhance the absorption of nitrogen，phosphorus，and potassium by melons，and is an effective way to reduce nitrogen fertilizer application，improve quality，and increase yield.

Key words: Melon, Soil moisture, Nitrogen reduction, Mushroom substrates, Soil enzymes, Nutrition, Microorganisms