One of the basic factors of agricultural production intensification is using of mineral fertilizers, on the stake of that is no less as 30-50 % additional increase of harvest. Efficiency of mineral fertilizers is closely dependent on the soil-climatic conditions of a region, complex of growing technology and culture biology. Oat is called enough on improvement of soil nutrient regime, due to its well developed root system and to its high absorptive ability that is a substantial reserve of its grain productivity increase. However, in of Southern Steppe of Ukraine conditions this isue is not studied properly, since that crop is not widely grown. The purpose of our research is to define the influence of mineral fertilizers on soil nutrient regime in oat growing.

The research was conducted during 2006-2008 in farmstead «Ukraine» Ochakiv district of Mykolaiv oblast. The object of research were sorts of Chernihivsky 27 oat and Skakun oat. Soil of an experimental plot is chernozem southern weakly eroded clay loamy on loess’s, content of humus (for Тurin) is a 2,4 %, acidity – close to neutral (рН off 6,8).

The sowing plot area is 240 м², record – 25 м², repeated triple. The experiment agrotechnics was generally accepted for Southern Steppe of Ukraine. A predecessor was sugar beet. The following types of fertilizers were applied ammonium nitrate (N 34 %) and superphosphate simple (Р 20 %) with folding method under the preseed cultivating accordingly to experiment plan. The selection of the soil standards was carried out according to the generally accepted methodologies. Soil nutritive elements content was determined in a layer by a 0-30 cm during sowing and before harvesting of oat. Nitrate and ammoniacal nitrogen was determined for Кravkov, movable phosphorus and exchange potassium – for Chirikov.

The research has shown that of unfertilized variant of soil the content of nutritive elements in oat seedling stage for modern classification was average on nitrogen and potassium and there was an increase on phosphorus. Applying mineral fertilizers influenced the content of nitrogen connections in soil significantly. Applying nitric fertilizers in a dose of N₆₀ (on a background Р₄₀) increased the total amount of mineral nitrogen (N-NH₄ + N-NО₃) by 26,9 % compared to unfertilized background. Nitric fertilizers in a dose of N₉₀ (on a background Р₆₀) provided the most significant increase of total mineral nitrogen amount by 55,7 % compared with control.

Movable forms of phosphorus is one of important signs of soil fertility. In our research phosphorus was added in doses of Р₄₀ and Р₆₀ in different combinations with nitric fertilizers. It provided substantial increase of movable phosphates, but in lower percentage ratios compared with nitric fertilizers. The dose of Р₄₀ provided movable phosphorus content in relation to the control 5,1 % on average, and dose Р₆₀ – on 11,9 %. Our research has shown, that fertilizing of oat did not influence the content of accessible potassium in soil, that ranged within limits of a 26,2-26,7 milligram per kilogram of soil (mgs/kg) content without fertilizers 25 mgs/ kg.

During vegetation of oat accessible nutritive elements content in soil diminished due to their use by plants for forming harvest, microbiological activity, redistribution in soil layers and other processes.

At the end of vegetation the amount of nitrogen diminished by 1,64-2,06 mgs/kg depending on the variant of fertilizer. Most nitrogen was used by plants in the unfertilized variant (81,6 %), the least – on a background greatest in experimental dose of nitrogen N₉₀P₆₀ – 65,8 %.

Estimation of soil nutritive mode state on the amount of accessible nitrogen at the end of oat vegetation allows establishing the following changes: soil of unfertilized variant belongs to a group with very subzero content of nitrogen, fertilized – to the group with middle content of this element.

For completion of oat vegetation amount of movable phosphates in soil also diminished in all variants of experiment, but a phosphatization positively influenced on their content by comparison to control. There were less charges of movable phosphorus (7,6-9,2 %) on fertilized variants, than on unfertilized background (11,03 %). Charges of potassium for a vegetation were least and presented 1,0-1,7 mgs/kg to soil or 4,0-6,8 % depending on background of fertilizer.

Average three years greatest harvest on both sorts was got at bringing of most dose of fertilizers N₉₀P₆₀ – 3,45 т/ha, that on 16 % anymore than harvest on a control variant.

Thus, during oat vegetation most intensively from soil mineral nitrogen (65,8-81,6 %) is lost, and charges of phosphorus and potassium present according to 7,6-9,2 and 4,0-6,8 %. Maximal in experiment dose of mineral fertilizers (N₉₀P₆₀) allows more productively spending nutritive elements from soil, foremost, mineral nitrogen.

Thereby, on vegetation of plants used nutritive elements from soil, most nitrogen and phosphorus they consumed on the variant «without fertilizers» (accordingly 82 and 11 %), least – on a phone N₉₀P₆₀ (accordingly 66 and 8-9 %). An expense of potassium for vegetation was the least, and 4-7 % made depending on the fertilizer phone.

The greatest content of mineral nitrogen and movable phosphorus in soil was at use dose of N₉₀Р₆₀, this dose provided the most increase of harvest of oat grain.

Key words: oat, fertilizers, content of nitrogen, content of phosphorus, content of potassium, soil.