Effect of Changing Climatic Conditions on Chill Units Accumulation and Productivity of Apple in Mid Hill Sub Humid Zone of Western Himalayas, India

The present study was carried out during 2014-15 in the Kullu district of Himachal Pradesh, which is situated between 31o52’00" to 31o58’00" North latitude and 76o13’00" to 77o44’00" East longitudes. The cumulative chill units hours available for apple crop were calculated by using UTAH model for the period of 1986 to 2015 and a decrease of 6.38 chill units (CU) hours per year was recorded at Kullu Valley of Himachal Pradesh. Chill units for the last three decades i.e. 1986-1995, 1996-2005 and 2006-2015 also revealed a decreasing trend of the order of 63.79 CU decreased per decade.Monthly accumulation of chill unit hours during the same period for each winter month (November, December, January and February) revealed maximum decrease of 2.186 CU per year was observed for the month of February. Trend analysis of last five years 2011-2015 showed there was a huge decrease of 14.98chill units per year. Data on apple productivity in Kullu district for last decade (2005-2014) showed a decreasing trend of the order of 0.183 tons/ha /year as per the regression equation y = -0.183x + 5.745. Thus the climatic conditions have been projected to become unfavourable for apple cultiivation in Kullu district for comming year.