Comparitive evaluation of evapotranspiration parameters of okra in polyhouse for alternate growing media

Abstract

Water is considered as a critical resource for agriculture and supplying the right amount in the right time is essential for healthy plants and optimum productivity. This objective can be met only through scientific water management and judicious water application, which in turn requires proper scheduling of irrigation events. For most of the agricultural crops a relationship can be found between evapotranspiration and climate by introducing a crop coefficient (K c ), which is the ratio of crop evapotranspiration (ET c ) to reference crop evapotranspiration (ET o ). Hi-tech horticultural systems use protected cultivation with soil and soil less media as substrates. Evapotranspiration in open field and inside of polyhouse will differ due to the micro climatic variation. Water balance components in the mini lysimeter will be influenced by the atmospheric condition and the media used in the mini lysimeter. At present water requirement for open field vegetable cultivation is adopted as such as in polyhouse cultivation. Hence there is a need to study the consumptive use of crops in soil and soilless media inside the polyhouse. Field experiment on the comparative evaluation of evapotranspiration parameters in a naturally ventilated polyhouse for alternate growing media was done in a Naturally ventilated polyhouse in the research plot of the Department of Irrigation and Drainage Engineering, in KCAET campus, Tavanur. In the study, Non-Weighing Mini-Lysimeters were used to determine evapotranspiration parameters and to develop crop-coefficient curves for Okra for soil and soil less media. The study compares the data for soil and soil less media in order to quantify the properties of these medias on evapotranspiration. ET 0 was estimated by Penman montieth equation using CROPWAT model. Studies on crop morphological parameters indicated that plant growth and yield parameters were higher for soil media than soil less. Seasonal average ETc values of Okra for soil and soil less media were 4.23 and 3.1mm/day. The calculated values of Kc for the initial, mid and late seasonstages were 0.98, 1.5and 0.74 in soil. Soil less media values were 0.72, 1.16 and 0.5 for different stages respectively. It was observed that soil less Kc values were lower than the soil. This may be due to the higher water holding capacity of the soil less media, which resulted in lesser evapotranspiration. The results implied that water requirement is lower for soil less media compared to soil. The results of this study can be used as a guideline in the computation of water requirement of soil and soil less in polyhouse for Tavanur region. If the poly house irrigation is scheduled in such a way as to apply the right quantity of water enough to meet the evapotranspiration requirements of crops, considerable water saving can be achieved.