NH3 Volatilization from Aboveground Plants of Winter Wheat During Late Growing Stages

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. 9μg NH3 40 plant-1 h-1 respectively at late filling stage. However, fertilized plants rapidly increased the rates to 43. 4 and 52. 2μg NH3, 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 0.7μg NH3 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. 9μg NH3 40 plant-1 h-1, but 1.2μg NH3 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 NH3 40 plant-1 h-1 when 0.4 g N and 0.13 g P had been added to per kg soil, while 33. 7μg 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.

Determining N supplied sources and N use efficiency for peanut under applications of four forms of N fertilizers labeled by isotope^15N

Rational application of different forms of nitrogen（N） fertilizer for peanut（Arachis hypogaea L.） requires tracking the N supplied sources which are commonly not available in the differences among the three sources：root nodule,soil and fertilizer.In this study,two kinds of peanut plants（nodulated variety（Huayu 22） and non-nodulated variety（NN-1）） were choosed and four kinds of N fertilizers：urea-N（CONH_2-N）,ammonium-N（NH_4~＋-N）,nitrate-N（NO_3^--N） and NH_4~＋ ＋NO_3^--N labeled by^（15）N isotope were applied in the field barrel experiment in Chengyang Experimental Station,Shandong Province,China,to determine the N supplied sources and N use efficiency over peanut growing stages.The results showed that intensities and amounts of N supply from the three sources were all higher at middle growing stages（pegging phase and podding phase）.The accumulated amounts of N supply from root nodule,soil and fertilizer over the growing stages were 8.3,5.3 and 3.8g m^（-2） in CONH_2-N treatment,which are all significantly higher than in the other three treatments.At seedling phase,soil supplied the most N for peanut growth,then root nodule controlled the N supply at pegging phase and podding phase,but soil mainly provided N again at the last stage（pod filling phase）.For the whole growing stages,root nodule supplied the most N（47.8 and 43.0%） in CONH_2-N and NH_4~＋-N treatments,whereas soil supplied the most N（41.7 and 40.9%） in NH_4~＋ ＋NO_3^--N and NO_3^--N treatments.The N use efficiency was higher at pegging phase and podding phase,while accumulated N use efficiency over the growing stages was higher in CONH_2-N treatment（42.2%） than in other three treatments（30.4%in NH_4~＋-N treatment,29.4%in NO_3^--N treatment,29.4%in NH_4~＋ ＋NO_3^--N treatment）.In peanut growing field,application of CONH_2-N is a better way to increase the supply of N from root nodule and improve the N use efficiency.