Grain yield, economics and disease severity of rice (Oryza sativa L.) in response to foliar application of potassium nitrate

Keeping in view the physiological role of potassium and nitrogen in alleviating various stresses and reported yield improvement thereof, investigations were planned to study the effect of foliar application of potassium nitrate (13:0:45) on growth, yield, disease severity and economics of paddy. Investigations included three experiments over two years with five rice genotypes of varying maturity duration and grain number. Study revealed that foliar spray of potassium nitrate(1.0, 1.5 and 2.0 per cent) at boot stage caused numerical gain in number of filled grains per panicle as well as spikelet fertility (per cent), leading to improvement in grain yield of PR 124 and PR126 to the tune of 1.4 to 1.8 and 1.9 to 3.0 q ha⁻¹, respectively. Another study comprised two factors i.e. application stage (Boot, Anthesis, Boot + Anthesis) and potassium nitrate concentration (Control, 1.0, 1.5, 2.0 and 2.5 per cent). Application stages had no significant effect on yield, yield attributes and disease severity but application at boot stage was found promising as it gave highest net returns. Data also suggested that foliar spray of potassium nitrate @ 1.5 percent induced improvement in grain yield of PR 128 (4.1 q ha⁻¹), PR 129 (3.2 q ha⁻¹) and PR 121 (3.7 q ha⁻¹) over control (water spray) by way of improvement in spikelet fertility and panicle weight. Similarly, net returns with 1.5 per cent potassium nitrate spray were higher than control (water spray) by a margin of Rs. 3735 to 6339 per ha⁻¹. Potassium nitrate spray did not affect the severity of rice diseases(grain discoloration, false smut and brown spot). It is therefore suggested that foliar spray of potassium nitrate @ 1.5 per cent at boot stage enhanced productivity and net returns particularly in varieties having more grain number per panicle.