Effects of increased ammonia on root/shoot ratio, grain yield and nitrogen use efficiency of two wheat varieties with various N supply

The effects of elevated atmospheric NH(3) on growth and yield parameters of two winter wheat varieties, the high water and fertilizer-demanding variety Xiaoyan 6 (XY6) and the drought-resistant variety Changhan 58 (CH58), grown with two levels of N fertilization, were studied in Open-Top Chambers. The results showed that in combination with the high N treatment increasing the atmospheric NH(3) concentration to 1000 nl/l from the ambient level of 10 nl/l NH3 significantly (P < 0.05) reduced the biomass and the root/shoot ratios of the plants, especially in XY6 plants, mainly because it negatively influenced root biomass production at anthesis and mature stages. In addition, the grain yield of XY6 was by 1.51% higher, while that of CH58 was 13.2% lower, following exposure to the elevated atmospheric NH(3) concentration rather than the ambient concentration in combination with the high N treatment. In contrast, in combination with the low N treatment, elevated atmospheric NH(3) had significantly and non-significantly positive effects on the grain yield of XY6 and CH58 plants, respectively. The Nitrogen Use Efficiency (NUE) and related parameters were all lower in plants of both varieties exposed to the high atmospheric NH(3) concentration together with either the high or low N treatment