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

Abstract

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.