Impact of the proportionally applied organic and inorganic fertilizers on the damaging potentiality of yellow stem borer on rice

Abstract

Degree of deterioration to the paddy cultivar Swarna mashuri [MTU 7029]  by yellow stem borrer [YSB], Scripophaga incertulas [Walker] under different alternative doses of organic and inorganic N fertilizers was carried out during the kharif crop season of 2008-2010 at Cooch Behar, West Bengal, India. There was nine different proportional combinations of N fertilizers from both organic and inorganic sources. Farm yard decomposed manure, pressed mud, green manure with Sesbania acculeata and vermin-compost were the chief organic N sources. While commercially available urea granules was the only inorganic N source. Maximum incidence of adult YSB population [1.93⁺ 0.12 individuals /5n hills] and egg masses [2.82+ 52 egg mass / quadrate] were observed when 160 kg N/ha was applied as urea grannules. Incidence of YSB population [0.56+0.12 individuals /5 hills] and egg masses [1.12+0.35 egg mass / quadrate] were minimumn when the field fertilized was with 3.5 tons of verrmicompost alone. The count of dead heart’[16.12%] and ‘white head’[ 12.56%] was maximum when high doses of inorganic N fertilizers [160 kg N/ha] was applied. These value differed significantly from all other treatments. Lowerr yield under this treatment was due to comparatively higher incidence of the pest and excessive vegetative growth of the plants. Best yield was noted when bil-fertilizers in combination with chemical fertilizers are used. The yield was maximum [36.74q/ha] when green manure with S. Acculeata 45kg seeds/ha + 80kg N/ha was applied to the field. The next best yield obtained from the application of 80 kg N/ha +5 tones of farm yard manure/ha and the value was 32.80q/ha. Extend of pest infestation [1.06+0.13individuals/5hills and 2.05+0.35 egg mass/quadrate] and the yield [34.15q/ha] was moderate under combined application of green manure at 45 kg/ha and 80 kg N/ha.