NITROGEN FIXATION ACTIVITY, EMISSION OF N2O AND CO2 IN PEA AGROCOENOSES UNDER THE INLFUENCE OF FERTILIZERS AND PRE-SOWING SEEDS BACTERIZATION Volkogon V.V., Zhurba M.A. Institute of Agricultural Microbiology and Agricultural Production NAAS

The dynamics of nitrogen fixation, emissions of N2O and CO2 in pea agrocoenoses under the influence of different fertilization systems and pre-sowing seeds inoculation with microbial preparation Rhizohumin were studied in stationary field experiment on leached black soil (short crop rotation potatoes – spring barley – peas – winter wheat). It was observed that symbiotic nitrogen fixation process had become active on the second year aftereffect of 40 t/ha of cattle manure, green manure and use of low (N30P30K30) and medium (N60P60K60) doses of mineral fertilizers. Rhizohumin had significantly increase nitrogen fixation activity in all variants except of the one with manure. Increase of N2O emissions had corresponded to the increasing doses of mineral fertilizers. The use of biological preparation had ensured the reduction of gaseous nitrogen losses due to the initiation of plants development. Carbon dioxide emission values had depended on the type and dose of fertilizers. Rhizohumin had reduced the emission of gaseous carbon compounds in variants with different fertilizer backgrounds due to its extensive use in the formation of additional yield.

Recently, more attention is paid to the study of carbon changes in ecosystems associated with both global changes in carbon dioxide in the atmosphere and with the need in additional CO 2 to the metabolic processes of cultivated plants in order to improve their performance.
Thus, the purpose of our research was to determine the intensity of the processes of symbiotic fixation of atmospheric nitrogen, N 2 O and CO 2 emissions at peas growing on different fertilization backgrounds. Experiment crop rotation was as following -potatoes, spring barley, peas and winter wheat.

Materials and methods
Experiments replication -four fold. Plots location -randomized. Plots accounting area 50 m 2 .
The second year aftereffect of 40 t/ha manure (applied under potatoes) was studied. Fertilizers were applied in doses N 30 P 30 K 30 , N 60 P 60 K 60 and N 90 P 90 K 90 . Organic and mineral fertilization systems had stipulated the second year aftereffect of manure in combination with the direct effect of fertilizers applied in low doses (N 30 P 30 K 30 ). For green manure the oil radish was grown as an intermediate crop. Plant residues were put into the soil in spring by shallow (10 cm) plowing.
Peas of Deviz variety were grown in two experimental blocks -with and without pre-sowing seed inoculation with biological preparation Rhizohumin, included an active rhizobia strain and physiologically active substances of biological origin (TU U 24.1-00497360-003:2007). As it was established previously the use of biological preparation increases field germination and seeds vigor, promotes developed of root system and active legume-rhizobial symbiosis [4].
Symbiotic nitrogen fixation activity was determined in a dynamics with chamber method using the acetylene test [5]. Ethylene content in the samples was determined on a gas chromatograph "Chrom-4" with a flame ionization detector. Thermostat temperature 40 ºC; gas flow: hydrogen -15 cm 3 /min, nitrogen -100 cm 3 /min, air -500 cm 3 /min. Sorption steel column 3 m filled with Parapak Q 60-80 mesh sorbent was used.
To evaluate the emissions of carbon dioxide and nitrous oxide in the "soil -plant" system the closed chamber method with our modification was used [6,7]. Direct N 2 O emissions were observed by gas chromatography "Tsvet-500 M" with electron capture detector. Column temperature 40 ºC, temperature of evaporator 120 °C, temperature of detector 330 °C. Gas consumption -medium (argon and methane 95/5) -35 cm 3 /min. Sorption steel column 3 m filled with Parapak Q 60-80 mesh sorbent was used.
Peas yield and statistical analysis of the results was carried out by standard techniques [9]. Determination of the emission of nitrous oxide characteristics in the dynamic indicates a significant loss of gaseous nitrogen in the variants with the second year aftereffect of manure and variants with the second year aftereffect of manure + N 30 P 30 K 30 (Fig. 2). Rhizohumin in these variants has almost no effect on the process. In variants with mineral crop fertilization N 2 O emission had increased along with the increasing doses of fertilizers. Minimal losses at this we observed in the variants with N 30 P 30 K 30 .

Results
It should be noted that in variants with high dose of fertilizers N 90 P 90 K 90 the reduction of losses of gaseous nitrogen compounds were observed under the use of biological preparation. In our opinion the impact of microbial preparation on reduction of losses of gaseous nitrogen is occurred due the improvement of symbiotic properties of legume-rhizobial system (see Fig. 1) and the formation of additional yield (see below). Green manure had not influenced the increase of nitrous oxide emissions as compared with a control variant pea growing technology.
Average readings of nitrogen losses due to the N 2 O emissions are given in Table 1. The highest losses had occur at aftereffect of 40 t/ha manure and in the variant with organic and mineral fertilization.
The lowest values were observed on green manure background. Application of Rhizohumin had reduced the total losses in the variant without the fertilizers, with fertilization and green manure background.     The aggregated values of CO 2 losses are presented in Table 2 (Table 3).  Rhizohumin was shown to be an important factor influencing crop productivity. Efficacy of biological preparation was observed in all versions, but most of the yield increases from inoculation were detected in the variants with the lowest and average dose of fertilizers. Effect of Rhizohumin on those backgrounds was equivalent to the impact of fertilizer in dose not less than N 30 P 30 K 30 . It should be noted, that in those variants the highest indices of nitrous oxide losses reduction were observed, which confirms the hypothesis of additional nitrogen uptake to the constructive metabolism of plants.
Application of Rhizohumin combined with green manure and manure aftereffect was less effective, however, because of the low cost of used technologies still economically viable.
Thus, the relationship between the peculiarities of symbiotic nitrogen fixation, N 2 O and CO 2 emissions were established. Application of microbial preparation Rhizohumin at growing of pea plants on leached black soils and low mineral backgrounds enhances the activity of nitrogen fixation and reduces the emissions of nitrous oxide. The gain of additional yield in variants with Rhizohumin was accompanied by increased binding of CO 2 . Hence, it was shown that pre-sowing seeds inoculation can actively influence the circulation of carbon in ecosystems.