Hybrid rice response to nitrogen fertilization for midsouthern United States rice production

Limited data representing the southern U.S. production area exists for N nutrition in hybrid rice (Oryza sativa L.) cultivars. Experiments were conducted to evaluate the effects of N fertilizer rates and application timings on grain and whole milled rice yield for 'XL723'(RiceTec, Inc., Alvin, TX) as compared with widely grown inbred rice cv. Cocodrie on clay soils and Cheniere on silt loam soils. A factorial arrangement of cultivar, preflood (PF), particle differentiation (PD), and panicle emergence (PE) N rates were established in Louisiana, Mississippi, and Missouri for a total of three site-years each for clay and silt loam soils. On clay soils, XL723 grain yield increased with increasing PF-N rate reaching 12,332 kg ha(-1) at a PF-N rate of 202 kg N ha(-1). 'Cocodrie' grain yield did not substantially increase with PF-N >151 kg N ha(-1). Averaged across cultivars, a PD-N rate of 50 kg N ha(-1) increased grain yields by 729 kg ha(-1) when 101 kg N ha(-1) was applied; however, as PF-N rate increased, the effects of PD-N were not significant. On silt loam soils, grain yields were 327 kg ha(-1) greater when 151 kg N ha(-1) was applied PF compared with 101 kg N ha(-1). Furthermore, a PE-N rate of 50 kg N ha(-1) increased grain yield by 333 kg ha(-1). On clay soils, maximum whole milled rice was obtained when a minimum of 151 kg N ha(-1) was applied PF and 50 kg N ha(-1) was applied at PE. On silt loam soils, the 101 kg N ha(-1) PF rate produced 625 mg g(-1) whole milled rice for Cheniere, whereas, the greatest concentration (613 mg g(-1)) of whole milled rice for XL723 was produced with 202 kg N ha(-1). Finally, yield potential was 17 to 20% greater for XL723 compared with the inbred cultivars; however, at equal N rates, whole milled rice was higher with conventional inbred cultivars compared with XL723. Hybrid rice can be used in the southern U.S. rice-growing region to increase rice yield per unit of land area. Preflood N rates on hybrid rice should be equal to or greater than inbred cultivars. For practical implications, N management for hybrid rice should include a PE application to increase yield, whole milled rice, and also decrease the potential for lodging. As straw-strength increases with new rice hybrids, PF-N management should be reevaluated for increased yield potential.