日光温室番茄-西瓜轮作系统不同水氮处理氨挥发特征

为探究黄土高原地区日光温室果蔬栽培中氨挥发特征,在陕西省杨凌区选择当地典型的日光温室,设置4个不同的水氮处理,采用密闭式间歇抽气法监测番茄-西瓜轮作季的氨挥发特征.结果表明: 日光温室栽培土壤氮素转化快,施氮处理施肥后第1～2天氨挥发出现峰值,氨挥发峰值为0.26～2.02 kg N·hm^-2·d^-1,7 d左右各处理氨挥发通量相近;施氮处理间氨累积排放量无显著差异;相同施氮量条件下,降低灌溉量氨累积排放量两季平均增加了46.7%;不同种植季氨平均排放通量和累积排放量均表现为西瓜季高于番茄季,西瓜季高温促进了氨排放;土壤铵态氮含量、土壤孔隙含水量、0～5 cm地温和温室气温均对氨排放通量有极显著影响,而土壤pH值与氨挥发通量呈显著负相关关系.不同种植季氨挥发通量和累积排放量存在差异,降低施氮量可减少氨排放,相同施氮量条件下降低灌溉量增加了氨排放.

Ammonia volatilization under different nitrogen and water treatments of tomato-watermelon rotation system in solar greenhouse in Losses Plateau,China

To understand the characteristics of ammonia volatilization in Losses Plateau, an experiment was conducted in a typical solar greenhouse involving four treatments. Intermittent ventilation chamber method was used to measure NH₃ volatilization over the period of tomato-watermelon rotation. The results showed that nitrogen transformation was rapid in solar greenhouse system. The peak NH₃ volatilization rate appeared one to two days after fertilization with the range from 0.26 to 2.02 kg N·hm^-2·d^-1. The NH₃ volatilization lasted for about one week in all treatments. No significant differences were recorded in terms of cumulative NH₃ volatilization among all nitrogen fertilizer input treatments. The cumulative NH₃ losses further increased about 46.7% in two seasons under the same nitrogen application rate, however when irrigation application was decreased. The average NH₃ vola-tilization rate and cumulative NH₃ losses in watermelon season were higher compared to tomato season, which might be attributed to high temperature during watermelon season. Soil NH₄⁺-N content, water filled pore space, soil temperature of 0-5 cm layer and air temperature all had extremely significant effect on NH₃ volatilization rate, while a negative correlation was observed between soil pH and NH₃ volatilization rate. Between the different cropping seasons, the rate of NH₃ volatilization and cumulative NH₃ losses were different, and decreased with decreases in nitrogen input, while reduced irrigation volume increased NH₃ volatilization under the same nitrogen application rate.