“…However, this dosage is insufficient to enhance the level of readily soluble potassium in the soil. The potassium contained in manure is part of organic matter, which is more difficult to transfer to the soil solution, and therefore plants in such conditions use other forms of potassium compounds in chernozem (Nikitina & Vasylenko, 2019). The authors' research revealed an insignificant, average relationship between the content of mineral nitrogen in the 0-25 cm layer and sunflower yield (r = 0.41 ± 0.24), but a significant strong relationship was established between the content of mobile phosphorus in the 0-25 cm layer and sunflower yield (r = 0.87 ± 0.13), exchangeable potassium and sunflower yield (r = 0.72 ± 0.18).…”