EFFICIENCY OF MOISTURE USE BY WINTER WHEAT UNDER VARIOUS SOIL TREATMENT METHODS AND USE OF SIDE VEGETATIVE MASS FOR FERTILIZATION IN THE WESTERN FOREST-STEP OF UKRAINE

Abstract

The scientific article presents the results of studies on the influence of soil tillage methods and the use of crop rotation by-products on the yield and water consumption of winter wheat. The research was conducted in a long-term stationary field experiment under the conditions of the Western Forest-Steppe of Ukraine within a short-rotation crop sequence: winter wheat – sunflower – maize for grain – soybean. The results concerning the effect of applying crop rotation by-products, both without and with compensatory nitrogen, under different primary soil tillage systems are presented for the period 2021–2023. The stationary experiment tested the following tillage systems: plowing to a depth of 20–22 cm, disking to 15–17 cm, and disking to 10–12 cm. The results of winter wheat grain yield assessment demonstrated a significant increase due to the application of by-products (soybean straw as the preceding crop residue), amounting to +2.1% under plowing, +2.8% under disking at 15–17 cm, and +2.7% under disking at 10–12 cm. The incorporation of the preceding crop straw together with a compensatory nitrogen dose (N7) resulted in an increase in winter wheat grain yield compared to the straw removal treatment by 5.6% under plowing, 6.0% under disking at 15–17 cm, and 7.9% under disking at 10–12 cm. The study established a consistent pattern of a significant decrease in winter wheat grain yield with decreasing tillage depth, due to reduced access to soil nutrient reserves: under plowing, yield was the highest (7.00 t/ha), whereas under disking at 10–12 cm it was lower by 9.7%, and under disking at 15–17 cm the reduction was only 1.9%. The use of the preceding crop by-products as an organic fertilizer contributed to an increase in winter wheat yield by 0.15 t/ha under plowing, 0.19 t/ha under disking at 15–17 cm, and 0.17 t/ha under disking at 10–12 cm. Nitrogen compensation in the application of preceding crop by-products proved to be most effective under minimum tillage (disking at 10–12 cm), resulting in a yield increase of 0.33 t/ha, or +5.1%, compared to the same treatment without nitrogen compensation. Overall, the effect of nitrogen compensation was also significant in other treatments, leading to an increase in winter wheat yield by 3.4% under plowing and by 3.1% under disking at 15–17 cm. On average over the years of study, total water consumption during the period from spring vegetation renewal to full maturity varied across treatments within the range of 356–369 mm (3.6%), indicating that neither tillage methods nor the use of by-products had a significant effect on this parameter. The water consumption coefficient primarily depended on yield; accordingly, depending on the methods of by-product utilization, the lowest values (49–51 mm/t and 50–52 mm/t) were observed under disking at 15–17 cm and plowing at 20–22 cm, respectively. The highest value of the water consumption coefficient (53–56 mm/t) was recorded under disking at 10–12 cm, which is explained by the significantly lower yield of winter wheat compared to other primary tillage systems.