Nitrogen effect on the incidence of Strigahermonthica (Del.) Benth in upland rice

Abstract

Field trials were conducted in the dry (Experiment I) and wet (Experiment II) seasons of 1997 at Samaru (11°11' N, 7°38' E, 686 m above sea level) in the northern Guinea Savanna ecological zone of Nigeria to study the effects of nitrogen rates on the reaction of upland rice (Oryza sativa L.) varieties to Striga hermonthica (Del.) Benth. The results indicate that FARO 48, a variety normally susceptible to Striga hermonthica, exhibited resistance. FARO 11 exhibited tolerance, while FARO 38, FARO 46 and FARO 45 exhibited susceptibility. The application of 90 and 120 kg N/ha delayed and reduced Striga emergence on the crop, induced a low crop reaction score and produced grain yields that were the maximum or significantly higher than the least. No significant differences in Striga infestation were observed between nitrogen rates of 30-120 kg N/ha. The significant interaction between upland rice varieties and nitrogen rates indicates that the susceptible varieties require higher rates of nitrogen to ameliorate the effect of Striga compared with the resistant varieties.