UDC 635.657:631.8 SYMBIOTIC NITROGEN-FIXING ABILITY OF CHICKPEA AND PRODUCTIVITY OF CROP AT DIFFERENT FERTILIZATION

Results of studying effect of mineral fertilizers in combination with inoculation with nitrogen-fixing bacteria on chickpea productivity in podzolic black soil of Right-Bank Forest-Steppe of Ukraine have been shown. Pre-sowing bacterization contributed to the active formation and functioning of the symbiosis, provided that the background of nitrogen fertilizers did not exceed 60 kg/ha. Under the influence of mineral fertilizers both separately and in combination with seed inoculation, chickpea yield increased by 10.8–15.2 hwt/ha compared to the variant without fertilizers and without inoculation. It was established that in order to obtain high and stable yields of chickpea seed in podzolic black soil of Right-Bank Forest-Steppe of Ukraine with low content of nitrogen of alkalihydrolyzing compounds and high content of mobile phosphorus and potassium, its fertilization system should include application of phosphate and potash fertilizers in the dose of 60 kg/ha during primary tillage, and nitrogen fertilizers – for presowing cultivation. Before sowing, seeds should be processed with the suspension of ammonium molybdate and Ryzobofit.

The development of nitrogen-fixing bacteria in the root systems of legumes is stimulated by molybdenum, which increases their productivity by 15-35 % depending on the soil-climatic conditions [6].
The inoculation of leguminous seeds reduces the need for nitrogen fertilizer application. Due to this, nitrogen nutrition improves and the immunity of plants to a number of fungal diseases increases [7].
The introduction of nitrogen fertilizers reduces the effectiveness of symbiosis, reduces the amount of nitrogen fixing nodules and their mass [10]. At the same time, one of the main factors providing stable nutrition of plants and improving the agrochemical parameters of soil in agrocenoses is a rational fertilizer system. To form a high chick-pea crop, plants must be provided with a balanced composition of nutrients in all phases of development, especially in critical periods [11]. In this regard, the objective of the study was to determine the effect of increasing doses of nitrogen fertilizers on the nitrogen-fixing capacity and productivity of chick-pea on a podzolic black soil of the Right-bank Forest-steppe of Ukraine, which seeds were inoculated with nitrogen-fixing bacteria. In the experiment, Rozanna variety of chick-pea was cultivated. The area of the experimental area was 54 m 2 , the accounting are -30 m 2 , the repetition of the experiment is three times with the randomised placement of variants. The technology of chick-pea growth in the experiment corresponded to the standard for the Forest-steppe of Ukraine. The predecessor is winter wheat.

Materials and methods
Fertilizers in the experiment were used as ammonium nitrate, carbamide, ammonium sulfate, double phosphate, potassium chloride, and ammonium molybdate. A two-year-old defecate with a CaCO 3 content of 70 % was used as the calcitic material; the dose of which was calculated by hydrolytic acidity.
The effect and interaction of two factors has been studied: Afertilization, B -Inoculation. Phosphate, potassium fertilizers and defecate were applied under fall plowing, nitrogen fertilizersunder pre-sowing cultivation and in a foliar mannerduring the phase of chick-pea beans formation as 20 % carbamide solution. Treatment of seeds by Ryzobofit suspension (based on the Mesorhizobium cicerii H-12) calculated as 10 6 bacteria per seed was carried out two hours before sowing.
The number and mass of nodular formations on the root system were determined by the method of H. S. Posypanov [12]; symbiotic nitrogen fixation was calculated on the basis of the accumulation of nitrogen by the mass of inoculated chick-pea plants. [13] Statistical analysis of the data was carried out by the analysis of variance method [14].

Results and discussion.
It was established that the formation of nodules on the roots of chick-pea plans significantly depended on nitrogen supply, as well as on the use of a bacterial preparation ( Table 1).
Determination of the total number and mass of nodules gives an opportunity to evaluate the potential of the symbiotic nitrogen fixation in plants. In the flowering phase, in variants with inoculation, a significant increase in the number of formed tubers on the roots of chick-pea plants was observed. The greatest number of them was formed in variants using Ryzobofit, in particular in the phosphoricpotassium background with starting doses of nitrogen fertilizers and liming of the soil. In variants with inoculation of seeds on phosphate-potassium background, the number of nodules The introduction of the maximum dose of mineral fertilizers P 60 K 60 + N 90 led to a decrease in the nodule formation activity. At the same time, the weight of the nodules was equal to the variant with calcification, the number of nodules increased by 13 units/plant, and their mass increased by 0.28 g compared to the control variant (without inoculation).
As for the inoculation of chick-pea seeds, this agro-measure was very effective. It contributed to an increase in the number of nodules and their mass in all variants of the experiment compared to the control variant. Mineral fertilizers to a lesser extent influenced the formation of nodules and their mass, in comparison with inoculation and their combined use, but among types of fertilizers it is necessary to note the positive effects of nitrogen fertilizers, provided that their dose should not exceed 60 kg/ha of active ingredient.
In order to take into account the role of culture as a nitrogen storage medium in soil, it is important to measure its content in the root plant remnants. Analyzing the data in the Table 2, it should be noted that the highest proportion of nitrogen in the root remnants (from its total content in biomass of plants) is noted in the variant without the introduction of mineral fertilizers -77.7 kg/ha or 43 %. Under the introduction of phosphorus and potassium fertilizers only, the accumulation of nitrogen in the root remnants was 74.0 kg/ha, and the share of total content in biomass decreased by 6 % compared with control. respectively, and its share was 32 and 29 % of total content in biomass. It was established that mineral fertilizers, as well as inoculation, contributed to the better formation of chick-pea grain. As seen from the data in Table 3