Rainfall study for dry land areas of selected districts of Tamil Nadu for crop planning

Abstract

Monthly rainfall data for 90 years from 1911 to 2000 and recent years weekly rainfall data from 1981 to 2010 for 30 years were collected from India Meteorological Department and used for analysis to propose alternate crops under dry land situation of three selected districts of Tamil Nadu (Dharmapuri, Tirunelveli and Villupuram). Based on the geographical location, the annual mean rainfall of the three selected districts did vary indicating spatial variability of rainfall in Tamil Nadu. The length of growing period was analysed employing three different methods namely Hargreave’s Moisture Availability Index, Jeevananda Reddy 14 weeks moving average and FAO water balance model. Conditional probability index was also computed for weeding and plant protection measures for the three districts. Under dry land situation, the shorter scale weekly rainfall analysis revealed 16 weeks growing period for Dharmapuri district and suggested crops were maize, ragi and mixture of sorghum, red gram and mochai. In respect of Tirunelveli district, the identified growing weeks were 12 and scientifically lesser Evapo-Transpiration requirement crops like pulses and minor millets had been suggested. For Villupuram district, the growing period was16 weeks and hence groundnut, sesame, maize, varagu and soybean had been suggested against cotton.