OPTIMIZATION OF FERTILIZATION AND ITS ROLE IN FORMATION OF PHYTOMASS PRODUCTIVITY OF RED CLOVER VARIETIES

Abstract

Sowing areas under red clover in Ukraine occupy more than 25% of the total cultivated area under perennial grasses, or more than 300 thousand hectares. Clover responds well to manure and peat-manure compost in an amount of 20-40 t/ha. When applying organic fertilizers it is necessary to consider their impact on cover crops, that there was no formation of a large vegetative mass and lodging. Therefore, manure is applied under forecrop. Among mineral fertilizers they are mostly used phosphorus-potassium, and if necessary nitrogen ones. Phosphate and potash fertilizers Р_60-90К_60-90 are applied under plowing. They are used by cover crops and clover plants. The rate of nitrogen fertilizer in barley should not exceed N_30-60, to prevent the lodging of crops. In the second year of vegetation the need for nitrogen fertilizers disappears. They are used only in weakened crops and marginal soils in small doses up to 30-45 kg/ha. In the fall or spring clover sowings are fed with phosphate and potash Р_30-60К_30-60 fertilizers. Clover refers to crops that grow well under acidic and neutral reaction of soil solution, at pH 5.5-7.0. Therefore, acidic soils are limed if necessary. The lime dose depends on the hydrolytic acidity of soil. Lime is applied in full rate by hydrolytic acidity under plowing or in terms of the lack of calcareous materials - surface before sowing in doses of 1-2 tons/ha. When pH is 4.5 the activity of legume bacteria almost stops. The methods of primary soil tillage depend on forecrop and cover crop. After cutting predecessor stubble forecrop they provide disc primary tillage. Plowing is carried out in mid-September at a depth of 25-27 cm. The areas with tilled forecrops, after which there are almost no crop residues, are usually immediately plowed. After harvesting corn and other crops, when there are many remains, the field is disked with disk tiller, and then plowed. In some cases plow is replaced by top soil dressing using heavy harrows or other equipment. This option is possible, but in these conditions the root system loses its ability to penetrate into the depth that can affect the grass stand productivity. In the first vegetation year red clover in terms of usage N₆₀Р₆₀К₉₀ and providing pre-sowing seed inoculation forms higher yield of leaf-stem mass with high content of dry matter by 12.2-12.3% when compared to the control. As it was found during research forming of the yield of red clover leaf-stem mass is largely influenced by the studied factors, namely: varietal features of the crop and fertilizers. It should be noted that the norms of mineral fertilizers and the growing method have also influenced the content of crude protein and fodder units in red clover. In the second vegetation year of red clover the highest content of dry matter showed the variant where it was provided seed inoculation with applying mineral fertilizers in the norm of Р60К90. The lowest content of dry matter approved to have the variants without applying mineral fertilizers and with no inoculation. Dispersive analysis demonstrated that among the studied factors the productivity of red clover plants is mostly affected by fertilizers and mowing. In addition, in the second year of vegetation higher productivity was formed by red clover stands cultivated with the use of seed inoculation. The lowest fodder productivity of red clover plants was found in the control, i.e. without using fertilizers and seed inoculation. Accounting of leaf-area duration in red clover during the vegetation period demonstrated that its value depends on the varietal features, the norms of mineral fertilizers and the growing methods. At the time of the first mowing red clover plants of the second vegetation year form higher indices of leaf-area duration when compared to the second mowing. This can be explained by the longer vegetation period and better water supply conditions. Red clover varieties cultivated with the use of mineral fertilizer (N₆₀Р₆₀К₉₀) and seed inoculation showed leaf-area duration higher than the variants without fertilizing and using rhizotorphin, but lower than the variant with using phosphate-potassium fertilizer. It was established that net photosynthesis productivity (NPP) of red clover stands increases with leaf-area index of 3.5. At that the values of other indices decrease gradually regardless of the variety, the fertilizing level, and the plant density. To obtain high and stable yields it is very important to have not only durable, but also high-performance photosynthetic apparatus, which is an indicator of net photosynthesis productivity, which characterizes the growth of dry matter per area per time. It’s revealed that the average net photosynthesis productivity in working productive crops reaches 5.6 g/m², maximum – 10-14 g/m² per day. Net photosynthesis productivity of clover is relatively low – on average during the vegetation season of about 3-4 g/m² per day. Analyzing how the indices of net photosynthesis productivity of different red clover varieties are influenced by cultivation methods and levels of mineral nutrition, it was found that the highest indices of NPP (3.39 g/m² per day) of Marusia red clover variety of the second vegetation year were seen in the variant without treating with rhizotorphin and without applying mineral fertilizers.