Tips on managing preflood nitrogen (N) under various soil conditions:
Dry soil: Use urea treated with a recommended NBPT product to minimize volatilization losses which occur when urea is left on the soil surface unincorporated by flood or adequate rainfall. Potential N shortfalls can be caught and corrected with no yield penalty postflood.
Muddy soil: Wait until around the final recommended time to apply N (based on a up-to-date DD50 report) before making risky decisions. Once you’re around that date, use urea treated with a recommended NBPT product and apply to field. Attempt to let the soil dry beneath the urea if possible, but if rain or conditions do not allow, then flood the field once you’re moving on past the final N date.
If muddy conditions are present and unlikely to dry before next rains, increase preflood rate by 10-20 lb N/acre and begin flooding. Under very poor conditions, consider a 20-30 lb N/acre rate increase.
Flooded field: If conditions create standing water through the final N date, set spills and begin applying N in a “spoon-feed” manner – 100 lb urea/acre once a week for 3-4 weeks. For hybrids, a minimum of 3 and possibly 4 applications of 100 lb urea/acre are needed to maximize yield. For varieties, a minimum of 4 and possibly 5 applications of 100 lb urea/acre are needed to maximize yield.
Nitrogen Rate Recommendations
The Nitrogen Rate Calculator is available to help get immediate N rate recommendations for most available cultivars. The calculator is built to account for N rate adjustments based on cultivar, soil texture (soil type), and previous crop. These are base recommendations and actual N rate used should be adjusted based on experience and additional tools such as N-STaR sampling and GreenSeeker readings.
* Base recommendations for rice following soybean on a silt loam soil.
† SPF = single preflood; PF = preflood; MS = midseason.
See 2021 Rice Management Guide for more details.