Dependence of above-ground mass formation of sickle alfalfa on application of different doses of mineral fertilizers in terms of permafrost floodplain soils of Yakutia, Russia

The experiments were carried out on the permafrost floodplain soils of the Khangalassky region of Yakutia to study the effect of different doses of mineral fertilizers on the formation of the forage mass of sickle alfalfa, the variety Yakutskaya yellow. The aim was to substantiate the effect of different doses of mineral fertilizers on the development of sickle alfalfa cultured in the permafrost floodplain neutral and carbonate soils in combination with floodplain saline soils. The tasks included the following ones: 1) to determine the effect of different doses of mineral fertilizers on the formation of the leaf surface of alfalfa plants; 2) to determine the dependence of alfalfa fodder mass yield on the application of mineral fertilizers. The size of the plots was 20 m2, with fourfold repetition, systematic placement of variants, wide-row sowing method by row spacing of 45 cm. There were 5 variants with different doses of mineral fertilizers in the experiment: 1) Without fertilizers; 2) N30 (PK)60; 3) N60 (PK)90; 4) (NPK)90; 5) (NPK)120. After the conducted studies, it was revealed that the application of mineral fertilizers in the dose of N60 (PK)90 provides the formation of the largest leaf area of ​​alfalfa (37.2 thousand m2 ha-1). The maximum dose of mineral fertilizer (NPK)120 contributes to plant foliage increase (up to 42%) and to the highest yield of crescent alfalfa dry weight (4.2 ton ha-1). Sprouting of alfalfa does not show dependence on the application of different doses of mineral fertilizers. A complete relationship was established between the yield of forage mass and the area of ​​alfalfa leaves (r = 1) with the regression coefficient of 0.6 ton ha-1. A strong dependence of forage mass yield was observed on leafiness (r = 0.9) with the regression coefficient of 0.4 ton ha-1, as well as an average negative dependence of the aboveground mass of alfalfa yield on the number of shoots (r = -0.6) with the regression coefficient of -0,5 ton ha-1.