Abstract
Nitrogen (N) fertilizers have their use efficiency adversely affected by the rate and source of N. A two-year field experiment was conducted to examine the yield response of upland rice by using NBPT (urease inhibitor), PCU (polymer-coated urea) and uncoated urea under different N application rates. It was hypothesized that either NPBT or PCU may result in increased yield components of upland rice when compared to conventional urea. The experiment was set up in a randomized block design in a 3 × 4 + 1 factorial scheme, with four replicates. Treatments comprised three sources (conventional uncoated urea, NBPT-treated urea, and polymer-coated urea) and four rates (30, 60, 90 and 120 kg ha-1) of N, in addition to a control treatment (no fertilizer application). Nitrogen fertilizers were applied in two split doses: 50% at the seedling stage, and 50% at the tillering stage (~80 days after planting). The results revealed that the use of enhanced-efficiency N sources increased the productivity and plant height of upland rice crop when compared to conventional urea. As compared to when it is untreated or polymner-coated, treating urea with NBPT resulted in increased 100-grain weight.
Highlights
Rice (Oryza sativa L.) is one of the major food crops for more than 3.5 billion (> 50%) people in the world (CGIAR, 2016)
Statisitical analysis show the differences in plant height, number of panicles, 100-grain weight, and productivity of rice between or among growing seasons, N sources and N rates (Table 2)
When the effect of N rates was analysed for each N source, maximum plant height was obtained with the application of N at a rate of 119 kg ha-1 by untreated urea (UU), 102 kg ha-1 by polymer-coated urea (PCU), and 81.25 kg ha-1 by NBPT-treated urea (NBPT) in the 2013/14 season
Summary
Rice (Oryza sativa L.) is one of the major food crops for more than 3.5 billion (> 50%) people in the world (CGIAR, 2016). In the case of rice, N fertilizers have their use efficiency adversely affected by the rate and source of N. The equilibrium of NH3-NH4 is shifted more to NH3, increasing volatilization losses that lead to lower fertilizer N use efficiencies (Ladha et al, 2005). Urease inhibitor NBPT [N-(n-butyl) thiophosphorictriamide] has been reported to significantly inhibit the activity of the urease enzyme, which reduces NH3 volatilization losses due to urea application to rice (Buresh et al 1988; Norman et al, 2009). A two-year field experiment was conducted to examine the yield response of upland rice by using NBPT, PCU and uncoated urea under different N application rates. It was hypothesized that either NPBT or PCU may result in increased yield components of upland rice when compared to conventional urea
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