Accumulation of Fertilizer Nitrogen-15 by Rice at Different Stages of Development
- D. Guindo,
- B. R. Wells and
- R. J. Norman
Results from fertilizer N recovery experiments with 15N have indicated high values of fertilizer 15N lost by rice (Oryza sativa L.). Field experiments were conducted to evaluate uptake of fertilizer 15N applied at preflood and at midseason and to determine the growth stage for maximum recovery of fertilizer 15N by rice under a dry-seeded culture system. Aboveground plant portions were sampled throughout the season for total dry matter, total N, and fertilizer 15N. Total N accumulation when N was applied in a single preflood application was maximum at heading + 21 d and then declined at maturity. When N was applied at preflood and midseason, total N accumulation continued until maturity. Fertilizer 15N recovered in the rice plant from the preflood N application was maximum (62%) at 21 d after application, and declined 10% by maturity. Fertilizer 15N from the midseason N application had maximum recovery (75%) in the rice plant at 7 d after application, and declined by 18% by maturity. Accumulation of total N in the panicle between heading + 21 d and maturity for the midseason N application was significant; however, it was nonsignificant for the preflood N application. Recovery of fertilizer 15N in the panicle did not differ between heading + 21 d and maturity for either the preflood or midseason N application. These results confirm earlier findings that sampling plants only at maturity will underestimate maximum fertilizer 15N uptake by rice.
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