EFFECT OF NITROGEN ON DEVELOPMENT OF ALTERNARIA BLIGHT CAUSED BY ALTERNARIA-SOLANI OF TOMATO (LYCOPERSICON-ESCULENTUM) IN RAINY AND WINTER SEASONS

Effect of nitrogen application in relations to concomitant weather fac tors was studied on the severity of the early blight [Alternaria solan i (Ell. & Martin Jones & Grout)] disease of tomato (Lycopersicon escul entum Mill. nom. Cons) in a field experiment for 8 growing seasons. Th e weather factors recorded 10 days preceding the disease observations showed augmentation in the severity at almost all dosage of N applied (0-250 kg N/ha at 11 levels at an increment of 25 kg/ha). Temperature (maximum and minimum) and the total precipitation increased the diseas e severity most significantly both in the rainy and winter seasons. Me an maximum temperature of 29.65 degrees C, minimum of 22.09 degrees C and the percipitation of 128 mm in the rainy season and those of 23.40 degrees C, 8.69 degrees C and 7.16 mm, respectively in the winter sea son favoured the disease-development. Higher relative humidity and the frequency of rain indirectly favoured, the disease-development. The d irect role of N levels in increasing the severity was not found signif icant. A dose of 150 kg N/ha in the rainy season and 175 kg N/ha in wi nter season was worked out to be optimum for the Alfisol of Chhotanagp ur plateau of Bihar.