Determining the Length of Growing Period (LGP) for efficient crop planning and sustaining farm productivity in the rainfed STZ of Karnataka

Abstract

The Southern Transitional Zone (STZ) of Karnataka with 70% of the area under rainfed farming is characterized by dry-sub humid to semi-arid climate. Even though the zone comes under the transitional belt, productivity levels in most of the rainfed crops is either low or uncertain due to uncertain rainfall, high rainfall variability and poor crop planning. Based on the Weekly rainfall or precipitation (RF) and Potential Evopotranspiration (PET) data of 52 Standard weeks for 20 years period (1996-2015) the length of the growing period (LGP) was worked out for the Zone. Successful crop production activities were possible for a period of 210 days starting from April 2nd Fortnight to November 1st week in this zone during which the precipitation is sufficient enough to satisfy the minimum Potential Evapotranspiration (PET) demand (RF/PET ratio of >0.50). However, the 26th standard week (RF/PET ratio of <0.50) in the growing season (May 4th week and partly July 1st week) was found critical for moisture for the kharif sown crops during which precipitation is not sufficient enough to meet the minimum PET demand of the crops/vegetation in the region. On the other hand, 41st- 42nd standard weeks (RF/PET ratio of >1.50) from middle September to 1st week of October could create water logged /saturated conditions in the field for the Rabi crop. Based on the LGP and the occurrence of dry or wet spells in the growing season, planting /sowing time and mid course correction measures can be planned for a particular zone/region for optimizing and sustaining the farm productivity.