Determination of the crop evapotranspiration (ETc) and crop coefficient (Kc) of the tomato crop grown in the greenhouse in spring season

In this study, it is aimed to obtain the water consumption in spring growing season in plastic greenhouses and plant coefficients in different development periods of tomato plant, which has the highest production and commercial potential in the Mediterranean Region where our country's greenhouse production is the most intense. The study also examined the relationship between leaf area index (LAI) values and the amount of photosynthetic active radiation (PAR). The experiment was carried out in the spring growing season in 2020, in a total of 6 drainage-type lysimeters, with three replications for tomato plants and turf, in a plastic greenhouse half covered with grass cover, located in Experimental Area of the Akdeniz University Faculty of Agriculture. Tomato seedlings were planted in the greenhouse on 24.02.2020 and the experiment was terminated on 29.06.2020. Irrigations were based on soil moisture deficit. All climatic data used in the study were obtained from automatic meteorology station in the greenhouse. The actual water consumption of the reference crop (grass) and tomato plant was measured in lysimeters in the greenhouse, and the plant coefficients of the tomato plant in different development periods were revealed. During the study, the reference crop (grass) water consumption (ETo value) was determined as 329.12 mm and the average ETo value was 2.61 mm day-1. Crop water consumption (ETc value) during the 127-days development period of tomato plants grown in the spring growing season under greenhouse conditions was obtained as 526.91 mm and average ETc value as 4.18 mm day-1. The average Kc values of the tomato plant grown in the spring growing period in greenhouse conditions were determined as 0.73 up to the 21st day (initial period) after planting tomato seedlings in the greenhouse; 1.49 between 21-84th days after planting (development period); 1.88 between 85-105th days after planting (maximum Kc period); and 1.63 between 105-127 days after planting (late period).Tomato yield was determined as 21.2 t da-1 in spring growing season. During the study, the average PAR values obtained from photosynthetic active radiation (PAR) sensors placed at three different heights such as the top, middle and bottom of the tomato plant canopy has been determined as 293.8, 162.4 and 149.2 μMol m-2 s-1 respectively. It is concluded that as the length of the plant increases, the radiation to the lower leaves of the plant decreases. A strong relationship (R2 = 0.83) between the leaf area index (LAI) and photosynthetic active radiation (PAR) ratiowas determined, and as the leaf area index value of the tomato plant increased during the study, the PAR ratio value measured in the canopy of the plant decreased.