Effect of mineral nutrients on spot blotch severity in wheat, and associated increases in grain yield

Spot blotch, caused by Cochliobolus sativus, is a serious disease of wheat (Triticum aestivum L.) in the warm lowlands of South Asia. A field study was conducted using two wheat varieties (Bhrikuti and Sonalika) during the 2001 and 2002 wheat seasons in Rampur, Nepal, to determine the effect of nitrogen, phosphorus, potassium, and chlorine fertilization on reducing spot blotch severity in wheat, and its associated increase in grain yield. Application of N alone reduced spot blotch severity by 8% in 2002. Phosphorus fertilization had no effect on spot blotch development. The balanced application of N, P, and K reduced disease severity by 15 and 22% in 2001 and 2002, respectively. Application of KCl as well as CaCl2 reduced spot blotch severity, but the former caused 11% greater reduction than the latter. The two varieties responded differently to the mineral nutrients’ effect on spot blotch severity, suggesting the nutrients’ importance in cultivar selection when considering the effect of soil fertility on susceptibility to foliar diseases. The lower disease severity and higher grain yield observed after the application of KCl compared to CaCl2 showed that KCl should be used on K-deficient soils in the warmer wheat growing regions of South Asia where spot blotch is a serious perennial wheat disease in intensive rice–wheat cropping systems.