Determination of Crop Water Requirement and Crop Coefficient at Different Growth Stages of Green Gram Crop by Using Non-Weighing Lysimeter

Abstract

Designing, establishing and managing irrigation projects, and scheduling irrigation requires estimating a crop seasonal water requirement. Lysimeter experiment conducted on green gram during Kharif season. His experiment was aimed at determining the seasonal crop evapotranspiration (ETc) and crop coefficient (Kc) of green gram crop for different development stages. Three non-weighing type lysimeters with dimension of 1 m × 1 m × 1.2 m were used to determine the daily ETc of green gram crop. Crop coefficient (Kc) was determined for each growth stages as the ratio of crop evapotranspiration (ETc) to that of reference crop evapotranspiration (ETo). The ETc was determined by soil water balance equation and ETo was computed by DSS-ET version 4.1. (A decision support system for estimation of crop evapotranspiration). Using FAO Penman-Monteith equation, the seasonal ETc was found to be 36.83 mm, 86.78 mm, 67.12 mm and 16.52 mm of water calculated for initial, crop development, mid-season and late season stages, respectively. The measured crop coefficient (Kc) values were 0.34, 0.45, 0.57, 0.69, 0.8, 0.99, 1.05, 1.13, 1.1, 1.04, 0.92, 0.66, 0.57, 0.42, 0.37 and 0.17 for the respective. Some of the crop coefficient values found in this experiment differed slightly from the average of FAO estimation but some lie in the range put for different environment. Thus, the observed difference indicates that there is a need to develop Kc values for a given local climate conditions and cultivars. Some crop yield and growth parameters were also collected in a sage-wise. The plant height and Number of primary, secondary and tertiary branches per plant were obtained at the mid-season stage, which was the highest from the four growth stages. The number of fruits per plant is 16 in mid-stage and 25 in late stage and the average maximum dry fruit weight per plant of Green gram was 8.12 gm.