ADAPTATION OF THE “PENMAN - MONTEITH” METHOD WHEN USING DRIP IRRIGATION FOR APPLE TREES ON THE ROOTSTOCK M-9 IN THE CONDITIONS OF THE STEPPE ZONE

Optimization of drip irrigation regimes for intensive apple orchards is the basis of agrotechnology for their cultivation with fruit yields exceeding 50 t/ha. There are many different ways of controlling irrigation regimes that enable to use individually or comprehensively relevant instruments, tools, computer programs, mathematical models etc. Using any approach is based on data on weather and soil conditions, biological and varietal characteristics of crop water consumption. The purpose of the research was to adapt the calculated method of determining the total water consumption (ETs) "Penman-Monteith" when using drip irrigation for apple trees on the rootstock M-9 in the conditions of the Steppe of Ukraine. The scientific-methodological approaches set out in the FAO 56 guidance were used when conducting the experiment. In the experiments, CropWat 8.0 computer program and iMetos digital weather station were used as tools to obtain data and calculate water consumption. When using the Penman – Monteith method, 6–10 vegetation irrigations with the rates of 620–700 m3/ha were conducted during the study period. With that the average yield of marketable fruits was 32.9 t/ha, and the average coefficient of irrigation efficiency was 31.5 m3/t. In production conditions, the actual total water consumption of apple trees when using the Penman-Monteith method was established as 3269.7 m3/ha, the reference water consumption (ETo) for this soil and climate zone during the growing season. In all phases of tree development, the ratio of apple coefficients (Kc) - typical one based on the recommendations of FAO 56 and calculated one, obtained based on the experimental data was established. A comparison of the actual value of the ETc and the calculated one using apple Kc according to the FAO 56 guidance was done. It is recommended that when determining the parameters of the drip irrigation regimes for apple trees on the rootstock M-9 in the Steppe of Ukraine when using CropWat 8.0 computer program and iMetos digital weather station to use the adjusted values ​​of Kc.