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.

Stability management of high speed axial flow compressor stage through axial extensions of bend skewed casing treatment

This paper presents the experimental results to understand the performance of moderately loaded high speed single stage transonic axial flow compressor subjected to various configurations of axial extensions of bend skewed casing treatment with moderate porosity.The bend skewed casing treatment of 33%porosity was coupled with rectangular plenum chamber of depth equal to the slots depth.The five axial extensions of 20%,40%,60%,80%and 100%were used for the experimental evaluations of compressor performance.The main objective was to identify the optimum extension of the casing treatment with reference to rotor leading edge which results in maximum stall margin improvements with minimum loss in the stage efficiency.At each axial extension the compressor performance is distinctive.The improvement in the stall margin was very significant at some axial extensions with 4%–5%penalty in the stage efficiency.The compressors stage shows recovery in terms of efficiency at lower axial extensions of 20%and 40%with increase in the peak stage efficiency.Measurements of flow parameters showed the typical behaviors at near stall flow conditions.Hot wire sensor was placed at the rotor upstream in the tip region to capture the oscillations in the inlet axial and tangential velocities at stall conditions.In the absence of casing treatment the compressor exhibit abrupt stall with very high oscillations in the inlet axial and tangential velocity of the flow.The extents of oscillations reduce with bend skewed casing treatment.Few measurements were also performed in the plenum chamber and salient results are presented in this paper.