Methodical approaches to yield estimation on the example of sunflower varieties and F1 hybrids bred at VNIIMK depending on the content of mineral nitrogen and mobile phosphorus in the leached chernozem

In 1993–1995, in the laboratory of agro-chemistry and in the department of seed production of V.S. Pustovoit All-Russian Research Institute of Oil Crops, the field experiments were carried out on devel-opment of varietal agricultural techniques of cultiva-tion and producing agroecological passports of 17 va-rieties and F1 hybrids of sunflower of three maturity groups – very early, early, medium. The yield, its struc-ture and quality of the studied varieties depending on weather conditions of the growing season (April – August) were recorded, agrochemical parameters of leached chernozem under varieties and hybrids in spring (April – May) were determined: forms of min-eral nitrogen (nitrate and ammonium) in the layer 0–60 cm, mobile phosphorus, the degree of mobility of phosphates, exchange acidity (pHKCl) in the layer 0–20 cm. The dependence of yield of each studied va-riety and hybrid by maturity groups and in the average of all studied varieties on the value of exchange acid-ity, the content of forms of mineral nitrogen, mobile phosphorus and the degree of mobility of phosphates was established. In the conditions of field experiments, the optimal content of mineral nitrogen, mobile phos-phorus and the degree of mobility of phosphates in the soil in spring, at the beginning of sunflower growing season, for varieties and hybrids by maturity groups was revealed, exceeding of which does not lead to an increase in yield. The varietal specificity of respon-siveness of the studied varieties and hybrids of sun-flower to the levels of content of mobile forms of nitrogen and phosphorus in leached chernozem is shown.