Spatial assessment of length of growing period for selected districts in Tamil Nadu

Length of growing period (LGP) provides information for crop suitability of farming systems and to study the climatevariabilityand change. LGPwasanalyzedand mapped usingthe FAO (Food andAgricultural Organization) model for extraction of start and end of the season and its variability for three selected districts (Salem, Tiruvarur and Sivagangai) in Tamil Nadu based on the criteria of cropping patterns, agro-climatic zones and rainfall and terrain characteristics. The observed daily weather data for different locations of the three districts were collected from various government agencies and gridded data for the period of 33 years (1981–2012). The results showed that LGPs obtained from the weather station data were found to be 9 to 30 weeks for different districts and the longest period of continuous supply of moisture for crop growth was found in Salem which had a wide range of two to seven months while for Thiruvarur and Sivagangai the LGP was shorter ranging from two to four months. These findings have an important application in cropping systems to ensure a better choice of crops under climate variability.