NH_3 Volatilization from Aboveground Plants of Winter Wheat During Late Growing Stages

摘要

Ammonia volatilized from aboveground parts of winter wheat was collected with an enclosure growth chamber and measured from jointing to maturing stage. The results showed that ammonia released from unfertilized plants grown in high and low fertility soils remained at low rates of 2.3 and 0.9 μg NH_3 40 plant~(-1) h~(-1) respectively at late filling stage. However, fertilized plants rapidly increased the rates to 43.4 and 52.2 μg NH_3 40 plant~(-1) h~(-1) in the high and low fertility soils, respectively, at the same period. The released a-mount was different in different parts of plants. At filling stage, lower senescing stems and leaves volatilized more ammonia than upper parts, i. e., ears and flag leaves that grew normally, with an average of 1.4 and 0.7 μg NH_3 20 plant~(-1) h~(-1) respectively, strongly suggesting that it was the senile organs that released large amounts of ammonia. At the grain filling stage, shortage of water supply (drought stress) reduced ammonia volatilization. The average rate of ammonia released under water stress was 0.9 μg NH_3 40 plant~(-1) h~(-1), but 1.2 μg NH_3 40 plant~(-1) h~(-1) with moderate water supply. Application of N together with P fertilizer resulted in a higher ammonia volatilization than N fertilization alone at the maturing stage. The average rate released was 135.3 μg NH_3 40 plant~(-1) h~(-1) when 0.4 g N and 0.13 g P had been added to per kg soil, while 33.7 μg when 0.4 g N added alone. Ammonia volatilization from plants was closely related with plant biomass and N uptake; P fertilization increased plant biomass and N uptake and therefore increased its release.