Effects Of Nitrogen Fertilizer And Winter Wheat Varieties On Canopy-atmospheric NH₃ Exchange

This study aimed to further explore the contribution of canopy ammonia exchange to ammonia volatilization in wheat field,and to reveal the mechanism of canopy ammonia emission in agronomic and physiological perspectives.The study was carried out in the winter wheat growing season of 2016²017 and 2017²018.The experiment set up‘Xiaoyan22’without nitrogen application,‘Xiaoyan22’nitrogen application 180kg N·hm^-2,‘Zhengmai 366’without nitrogen application,‘Zhengmai 366’nitrogen application 180kg N·hm^-2 four treatments,used a vented ammonia volatilization collection device to monitor the ammonia volatilization dynamics throughout the growth period.In this paper,the canopy-atmosphere NH₃ exchange dynamics of winter wheat in different growth stages were studied.The effects of dry and yellow leaves on NH₃ emission;the relationships between NH₃ volatilization and nitrogen metabolism indicators including nitrate reductase,glutamine synthetase activity,apoplast NH₄⁺and soluble protein content in leaves.At the same time,the grain yield and yield components of winter wheat,ammonia volatilization intensity,biomass,nitrogen use,nitrogen transport,and their relationship with canopy NH₃volatilization were examined.The main results of this study are as follows:（1）The NH₃ was absorbed by the shoots before Booting-flowering,which cut down ammonia volatilization in wheat field with 23%⁴0%;While NH₃ was emission from the shoots after the Booting-flowering,which contributed to total field ammonia volatilization17%²7%.Canopy ammonia exchanges under nitrogen application or fertile soils were more than that in the infertile conditions and without nitrogen.The effects of dry and yellow leaves on the canopy NH₃ emission were affected by variety,growth period and soil fertility.（2）The canopy ammonia emission had a significantly positive linear relationship with soil temperature,apoplast NH₄⁺concentration and soluble protein,and a negative linear relationship with glutamine synthetase activity and nitrate content markedly.（3）Nitrogen application had a significant positive relationship between grain yield,grain number per spike,thousand grain weight and wheat biomass and canopy ammonia volatilization（P<0.05）.The soil ammonia volatilization intensity was affected by nitrogen fertilizer and soil fertility.Nitrogen application can reduce soil ammonia volatilization intensity by 52%,high fertility land,soil ammonia volatilization intensity was 4.12 kg N·t^-11 grain,and low fertility land was 2.16 kg N·t^-1 grain.The intensity of wheat field was affected by nitrogen fertilizer and variety.Nitrogen application can reduce the volatilization intensity of ammonia in wheat field by 65%,and the volatilization intensity of ammonia in wheat field was 5%-6%higher than that of Zhengmai 366.（4）The nitrogen uptake and grain nitrogen uptake of winter wheat were affected by nitrogen fertilizer and soil fertility.Nitrogen application could increase nitrogen uptake and grain nitrogen uptake by 15%-229%and 13%-210%.Nitrogen transport in winter wheat was affected by nitrogen application and variety.Nitrogen fertilizer can increase nitrogen transport in leaves,stems and hulls by 10%-410%,17%-37%and 38%-72%.Nitrogen transport in stems and hulls were 4%-13%,0.7%-76%and 27%-31%higher than Zhengmai366.There was a significant positive linear relationship between ammonia volatilization and nitrogen uptake and nitrogen uptake（P<0.1）.Nitrogen transport in winter wheat leaves was significantly positively correlated with canopy ammonia volatilization（P<0.1）.The nitrogen transport efficiency of winter wheat leaves and stems was significantly negatively correlated with canopy ammonia volatilization（P<0.01）.