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The results of statistical modelling for the yields prediction of spring row crops, namely, maize, sorghum and soybean, depending on the values of the remotely sensed normalized difference vegetation index (NDVI) at critical stages of the crops growth and development were presented. The spatial NDVI data obtained from the Sentinel-2 satellite were used to create the models. Quadratic regression analysis was applied to develop the yielding models based on true yield data of the crops obtained in the period of 2017 and 2018 at the experimental field of the Institute of Irrigated Agriculture of NAAS, Ukraine. The results of statistical modelling revealed that the method is suitable for precise yield prediction, and the best stages for NDVI screening and use in this purpose are different for the studied crops. The best accuracy of prediction could be obtained at the stage of tasselling (VT) or silking (R1) for maize (the mean absolute percentage error MAPE is 8.75%); at the stage of second trifoliate (V2) for soybean (MAPE is 3.75%), and at the stage of half bloom (S6) for sorghum (MAPE is 17.62%). The yield predictions by NDVI are reliable at a probability level of 95% (p < 0.05).

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Efficient water management in agriculture is an important part of the general programme on water resources preservation. This study is devoted to the determination of the effects of soil processing system and mineral fertilization on the water use efficiency and productivity of grain corn (Zea mays Linnaeus, 1753). The trials were conducted in 2017–2018 on irrigated land in the South of Ukraine. The field experiments were carried out on the experimental plots of the Institute of Irrigated Agriculture of the NAAS in four replications. We studied the following agrotechnological parameters and their combinations: Factor A – primary tillage type and depth within different tillage systems in the short crop rotation (grain corn – grain sorghum – winter wheat – soybean); Factor B – application rates of mineral fertilizers (N0P0, N120P60, N180P60). We established that the highest yield of grain accompanied by the best water use efficiency was provided by the cultivation technology with disk cultivator tillage on the depth of 8–10 cm within the differentiated tillage system in the crop rotation under the maximum nutritive background of N180P60. This agrotechnological variant resulted in a corn grain yield of 14.51 and 14.59 t/ha in 2017 and 2018 years of the study, respectively. The coefficient of water use efficiency, which is the relation of the water used by the crop to the yield, in this variant was the lowest – 39.6 and 42.0 mm/t in 2017 and 2018, respectively, which indicates the optimum response of corn grain to watering. The worst indexes of water use efficiency and corn productivity were determined in the experimental variant with disk cultivator tillage on the depth of 12–14 cm within the subsoil tillage system within the crop rotation under non-fertilized conditions. We determined that strengthening of the crop nutrition under the rational tillage system in crop rotation is helpful in optimization of the crop water use in the irrigated conditions of the South of Ukraine, which is very important in the current conditions of freshwater scarcity.

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