Effects of nitrogen fertilizer levels and split N application on N-use efficiency of irrigated rice (Oryza sativa L.) in the north of Iran

153/99 1399/07/28 مقالات علمی 80 امتیاز کار گروه

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Abstract Optimum rate and timing of nitrogen fertilizer application are crucial in achieving high yield and N-use Efficiency (NUE) in irrigated rice. Effects of nitrogen fertilizer levels and split N application on Agronomic Efficiency (Ea), N-utilization Efficiency (Physiological Efficiency; Ep), and N-uptake Efficiency (Recovery Efficiency; Er) of irrigated rice (Oryza sativa L.) Cv. Khazar was evaluated in a Randomized Complete Block Design (RCBD), with three replications in a light texture sandy soil at Guilan province in the north of Iran in 2003. Effects of six N fertilizer rates and and their split application: T1= control (no N fertilizer), T2= 40 (basal), T3 =40+40 (basal + midtillering), T4= 40+20+20 (basal + midtillering + panicle initiation), T5= 60+60 (basal + midtillering) and T6=60+30+30 (basal + midtillering + panicle initiation) kg/ha in the form of urea were compared. N contents of shoot and grain were measured by micro-kjeldal digestion and distillation at physiological maturity stage. Results showed that grain yield in triple split application of N fertilizer treatments (4832 and 4668 kg/ha in T6 and T4, respectively) were significantly higher than double splitting treatments (4367 and 4191 kg/ha in T5 and T3, respectively). Grain yield increment ratei n fourth and sixth treatments were 36.6% and 34.4% in comparison with control (3062 kg/ha). The highest Ea, Ep, and Er were observed in the fourth treatment by 20.1, 30.1, and 66.9% respectively. Grain N uptake increase rate in fourth and sixth treatments, were 77.8% and 95.3% compared to the control (32.1 kg/ha).The highest Nitrogen Harvest Index ( NHI ) was related to the fourth treatment too (0.44 ). The grain yield was not significantly differ in the fourth treatment in comparison with sixth one, but the higher Ea, Ep and Er may lead to economize nitrogen fertilizer application and its less leaching in light texture soils at the coastal paddy fields in the north of Iran.

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