Evaluation of nitrogen efficiency on grain sorghum (Sorghum bicolor L. Moench) genotypes

Yield increase of crop along with human health and environment persistence could obtain from correct use of nitrogen fertilizer. In this study the effect of different regime N application on N efficiency grain sorghum genotypes in 2009 growing season at the Khorasan Razavi Agriculture Natural Resources Research Center Mashhad was investigated. Split plots experiment in base of randomized complete block design was conducted with three replications. The main plots were allocated to three genotypes (Sepideh cultivar, M2 and M5 promising lines) and the subplots consisted of photosynthesis status (non disturbance and disturbance current with potassium iodide) in factorial combination with three N regimes (0, 100, 200 kg/ha from urea fertilizer). The results of variance analysis showed that the nitrogen had significant (P ≤0. 01) effect on nitrogen recovery efficiency (NRE) agronomic N use efficiency (ANUE), physiological N efficiency (PNE), grain yield and harvest index (HI). NRE percent in no N application and N application at 100 kg.ha-1 treatment were 82.34 and 68.31, respectively and increased 43.05 and 18.67 compared with 200 kg.ha-1.The highest agronomic N use efficiency and physiological efficiency obtained in no N application (36.23g grain per N g N applied and 43.45 g grain per g N absorbed respectively) and had107% and 43.02% increased compared to 200 kg.ha-1 treatment. In spite of increased in nitrogen efficiency (three traits) by decreased in N applied, the highest and significant yield obtained in N application at 100 kg.ha-1 (6.47 t.ha-1) compared to no N application(5.44 t.ha-1). Photosynthesis status had significant effect on ANE, RNE and PNE also. Non disturbance in current photosynthesis dramatically increased amount of these three N efficiency traits (29.26 g.g-1, 72.33% and 39.55 g.g-1) respectively.