Role of potassium on insect pests and diseases of puddled transplanted rice cv. Lalat in Odisha

Abstract

Potassium (K) is one of the most important essential nutrients for rice crop. The role of K in enhancing rice productivity is well established. It also imparts resistance against diseases and insect-pests. A field study was conducted to evaluate the effect of different levels of K application on the disease and insect pest incidence of puddled transplanted rice during dry season (DS) 2013–14 and wet season (WS) 2014 involving 9 potash management options in 3 replications. The experimental soil was highly deficient in exchangeable K (25.85 mg/kg). Increase in K dose from recommended 40 kg/ha to 80 kg/ha significantly reduced all insect pest and disease incidence. Recommended dose of K 40 kg/ha along with one foliar spray of 1% KNO 3 at flowering was also effective than other treatments. Reducing fertiliser K to 50% and adding straw (3 t/ha) was not as effective as full dose of K, but had moderate effect on pest incidence. Both blast and brown spot incidence correlated negatively with K content in leaf at maximum tillering (MT) and panicle initiation (PI) stages with more correlation at MT stage (r= -0.59, -0.69) than PI stage (r= -0.48, -0.37) in dry season and PI stage (r=-0.51, -0.73*) than MT stage (r= -0.48, -0.37) in wet season. Insect attack in both dry and wet seasons negatively correlated with K content in leaf at MT and PI stages with wet season having stronger correlation than dry season for all the major insects. From the study, it is also evident that not only the leaf K content, but K-N balance is also important for making the plant resistant to insect pest and disease attack. Thus, K nutrition is important for control of most common insect pests (stem borer, leaf folder, whorl maggot and Gundhi bug) and diseases (blast and brown spot) in rice.