Rice Grain Yield and Nitrogen Uptake as Affected by Urea Amendment and Rainfall Timing. (1st November 2017)

• Record Type: Journal Article
• Authors: Dempsey, Randy J.; Slaton, Nathan A.; Roberts, Trenton L.; Norman, Richard. J.
• Is Part Of: Agronomy Journal. Volume 109:Number 6(2017)
• Page Start: 2966
• Page End: 2973
• Publication Date: 2017-11-01
• Subjects: Agronomy -- Periodicals; 630
• DOI: 10.2134/agronj2017.04.0216
• Languages: English
• ISSNs: 0002-1962

Abstract

Abstract : Core Ideas: Use of NBPT‐treated urea maximized N uptake and grain yield of rice regardless of soil moisture. Rainfall between urea application and flooding may be detrimental to rice grain yield. Dry soil conditions before and after urea application maximize fertilizer‐N recovery by rice. Nitrogen loss in the delayed‐flood method of rice ( Oryza sativa L.) production is minimized by applying urea to a dry soil, use of a urease inhibitor, and immediate flooding. The time required to flood fields is often a factor limiting fertilizer‐N recovery. Our objectives were to compare the effects of simulated rainfall timing, N‐(n‐butyl) thiophosphoric triamide (NBPT) rate, and nitrapyrin (NP) rate on rice aboveground‐N content and grain yield. Field experiments evaluated rice growth as affected by NBPT rate (0 and 0.89 g NBPT kg −1 urea), NP rate (0 and 572 g NP ha −1 ), and three simulated rainfall timings (no simulated rainfall [NOSR], simulated rainfall before nitrogen [SRBN], and simulated rainfall after nitrogen [SRAN]). Yield was unaffected by simulated rainfall timing when rice was fertilized with NBPT‐treated urea (7904–8264 kg ha −1 ). When rice was fertilized with untreated urea, grain yields were greater with NOSR than with SRAN or SRBN. Within each simulated rainfall timing, rice yields were 6.9 to 21.3% greater when NBPT‐treated urea was applied. Nitrapyrin rate had no effect on yield in 2013, but, compared to untreated urea, NP‐treated urea decreased yield by 5.6% in 2014. Application of urea to moist soil followed by dry conditions or dry soil followed by rainfall are field environments that result in lower yields presumably to fertilizer N loss than when urea is applied to a dry soil that remains dry until rice is flooded. Use of urea amended with NBPT maximized grain yield in each simulated rainfall scenario.