Fertilizer Nitrogen Uptake by Rice from Urea-Ammonium Nitrate Solution vs. Granular Urea
- C. E. Wilson ,
- B. R. Wells and
- R. J. Norman
Granular urea is the primary N fertilizer source for rice (Oryza sativa L.) production in the southern USA. New cultivars respond to higher rates of N fertilizer applied preflood. Application of high rates often results in distribution problems when granular urea is used as the N source. Because liquid fertilizer sources can reduce distribution problems, this study was initiated to evaluate the efficiency of urea-ammonium nitrate solution (UAN, 28-0-0) as a N source for rice. Each N fertilizer source was applied in three split applications at a rate of 84 kg N ha−1 just prior to flooding (preflood), 33.6 kg N ha−1 at 1.3-cm internode elongation (IE), and 33.6 kg N ha−1 10 d after IE (IE + 10d) onto ‘Newbonnet’ rice that was seeded into microplots (0.58 m2). The fertilizer sources consisted of granular urea or UAN with either the urea, NH4, or NO3 labeled with 15N at each application time. At all three application times, the highest fertilizer N uptake occurred when granular urea was the N source. Application of granular urea resulted in 72.5% recovery of the fertilizer N in the plant compared with 52.6% recovery of the fertilizer N from UAN. Application of granular urea also resulted in significantly higher grain yields than UAN. Granular urea was superior to UAN as a N source for rice production due to the inefficient uptake of NO3-N from the preflood application (9.8%). However, these data show that rice can efficiently utilize NO3-N from applications made at IE or later (73.7% recovery).Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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