Nitrogen Uptake Efficiency of a Hybrid Compared with a Conventional, Pure‐Line Rice Cultivar

Hybrid rice ( Oryza sativa L.) hectarage has increased substantially in the southern United States and necessitated research into the N nutrition of this new type of rice and how it compares to the traditional pure‐line rice. Consequently, a study was conducted utilizing 15 N‐labeled urea applied at a range of N rates on two silt loam soils differing in native soil N to evaluate and compare the N fertilizer uptake efficiency, the native soil N uptake, and total N uptake of a RiceTec hybrid and a pure‐line rice cultivar. The hybrid (60.5 kg N ha −1 ) had greater soil N uptake compared with the pure‐line cultivar (51.7 kg N ha −1 ). The hybrid had a higher fertilizer N uptake efficiency (FNUE) compared with the pure‐line at the location with the lesser native soil N (62.2 vs. 56.2%, respectively), but had a similar FNUE at the location with the greater soil N (63.8 vs. 60.0%, respectively). Also, the pure‐line had a higher FNUE and greater N fertilizer response at the location with the greater soil N while the hybrid had a similar FNUE at both locations. The greater total N uptake by the hybrid compared with the pure‐line was due to greater soil N uptake at both locations and fertilizer N uptake at the location with the lower native soil N. The results suggest that if the native soil N is below a critical level a pure‐line rice cultivar might benefit from a higher rate of N fertilization to maximize FNUE.