TREND ANALYSIS OF RAINFALL IN FCV TOBACCO GROWING AREA OF HUNSUR UNDER KARNATAKA LIGHT SOILS

Abstract

Tobacco (Nicotiana tobacum) is grown in red sandy loams called as Karnataka Light Soils as a Kharif crop as rainfed and irrigated when required. The study area Hunsur is in southern transition zone of Karnataka with a mean annual rainfall of 748 mm is a part of Mysore district which contributes about 80 % FCV tobacco grown during Kharif as rainfed. Crop growth generally affected when there is a moisture stress during the critical stages, it is more applicable to FCV tobacco where the economic produce is leaf. It is become more pertinent when crop is grown in light textured soils. Hence, a trend analysis was done for detecting and estimating trend in time series of annual values of monthly rainfall of Hunsur area (2001-2015) under FCV tobacco. The used statistical techniques were the nonparametric Mann-Kendall test for testing the presence of the monotonic increasing or decreasing trend and the nonparametric Sen’s method for estimating the slope of a linear trend. It was found that a decreasing trend in monthly rainfall during MayJune-July months significantly during June with z test value: -0.79, -1.68 and -1.54 and Sen’s estimator of slope (Q) i.e. magnitude of change was highest significantly (- 9.44 mm/year) in June followed by July (- 4.55 mm/year) and May (- 3.60 mm/year) which is a critical period of Kharif grown FCV tobacco. Such aberrations in rainfall during this period result in poor yield and quality which can be mitigated to avoid moisture stress. Practicing rainwater storage and recycling (farm pond technology) for providing life saving irrigation is essential to maintain required soil moisture in the root zone of the crop. Little adjustment in planting time, if required may help in better yields and quality in FCV tobacco in the study area.