The results of the study devoted to assessment of accuracy and reliability of the CROPWAT 8.0 software application calculations of the evapotranspiration and crop water requirements are represented in the article.The study was based on the results of the perennial field experiments, conducted during the period from 2012 to 2017 at the irrigated lands of the South of Ukraine with different crops, namely: sweet corn, grain corn, soybean, sorghum. We assessed accuracy of the CROPWAT 8.0 software application by the comparison of the calculated values with the real ones. We determined considerable differences between the calculated crops evapotranspiration values and crops irrigation requirements and the real ones obtained in the field experiments. The difference was the most essential in case of the drip-irrigated sweet corn crop and averaged to 46.05% for evapotranspiration and 89.20% for irrigation water requirements, correspondingly. Overhead sprinkler irrigated crops are likely to be more suitable for accurate evapotranspiration prediction by using the CROPWAT 8.0. The slightest discrepancy between the calculated and actual values of the studied parameters were determined on the overhead sprinkler irrigated grain corn crops, where the differences averaged just to 15.86% for evapotranspiration and 41.63% for irrigation norm. The results of the study gave us an opportunity to conclude that CROPWAT 8.0 software application should not be used without previous calibration and adjustment of the crop coefficients for the concrete agricultural production conditions.
Expansion of variety and sustainable production of quality oilseed crops both in the world on the whole and in Ukraine in particular, is actual. The main factors of this are: the urgent need for raw materials, changes in weather and climatic conditions, changes in the structure of phytocenoses, development and spread of specific diseases and pests, and adaptive ability of species and varieties, etc. This problem is especially crucial when cultivating crops under stressful conditions of the Southern Steppe of Ukraine. In the cultivation of sunflower varieties and hybrids of modern plant breeding, we observe a pronounced reaction to changes in agricultural meteorological conditions of their cultivation. Our research was carried out for three years (2017-2019) in the Southern Steppe region of Ukraine, which has low rainfall. The methods of the analysis were field and mathematicalstatistical methods. We evaluated the levels of environmental plasticity in 23 sunflower hybrids. We used the Eberhard and Russel method (the plasticity and stability analysis) to fully evaluate new hybrids with regard to their adaptability to growing conditions and investigate the appropriate rate of response of genotypes to the growing technology. We have found that under the conditions of the Dry Steppe zone of Ukraine sunflower embodies its genetic potential by 45%. Based on the experimental data, we conducted the regression analysis resulting in a linear regression model that indicates the dependence of sunflower yield on agricultural meteorological indicators. The hydrothermal coefficient in 2017 was 0.75. Despite this, the sunflower plants formed the highest yield that year due to the sufficient minimum relative humidity of the air during flowering (BBCH 61-65) was 54.7%. Creating genotype shave an average value of plasticity of the yield (ranging from 0.83 to 1.19), namely: EU Arcadia SU, EU Genesis, NS-X-496, EU Generalis SL, EU Loris KLP, SI Bacardi KLP, SI Arizona. Hybrids of different intensity levels, that are genetically and biologically diverse, can be cultivated efficiently in different agricultural ecological growing zones.
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