INFLUENCE OF NITROGEN FERTILIZATION ON THE BACTERIA AND VEGETABLE SEED SYMBIOSIS|
Lucian HALMAGEAN, Monica ZDREMTAN, Liliana CANTAR, Ioan CALINOVICI
"Aurel Vlaicu" University, Arad, Faculty of Food Industry, Tourism and the Environment Protection, str. Dragoi nr. 3, 2900 Arad, Romania (contact e-mail: firstname.lastname@example.org)
Lately, there has been a great interest in the effect that the nitrate fertilizers have on the vegetable production and in the interaction that it has with the bacterization. This interest is national but also international. A lot of foreign research works showed the depressive or the stimulating effect of the fertilizers containing a small amount of nitrogen as compared to the reduced effect of the fertilizers containing a big amount and being bacterized. Some of the results shoe that the surplus of nitrates determines the deregulation of bacteria entrance biochemistry into the rooty system and thus the formation of a reduced number of nodosities.
Our aim was to study the efficiency of the symbiosis between the seeding garden bean and the shoot of the Rhizobium pheseole-Biotrofin depending on the nitrogen fertilization, clarifying in this way some aspects concerning the nitrogen nutrition of the seeding garden bean.
Material and methods
The experiments were made between 1996-2001, in the agro-ecological area of Arad, an area representative for the Western part of the country. We used the Valja kind we had continuously 55 plants/m2 on the field. The seeding period was 26-30 April.
The experiment with three differently graduated factors (irrigation, bacterial treatment and nitrogen fertilization) took place in lots under-divided with variants represented three time and the lot area was 15 m2.
The bacterial product used for treating the seeds was Biotrofin, a product with two live components: a nitrogen-catching bacterium, which catches its necessary nitrogen from the atmosphere, and another bacterium, Bacillus megaterum, which solubilizes the three-calcic phosphate making it accessible for the plants.
The data interpretation was made according to a variance analysis method applied for experiences made in the same area during several years.
Results and discussion
The action of the irrigation factor during the studied period has as results the crop improvement from distinct to very significant and, compared to the years average, very significant (the crop difference-0.297t/ha). The seeds bacterization previously to seeding was one of the conditions necessary for improving the crop of every year and for the whole period. The differences were very significant (2.076-2.281t/ha). The nitrogen fertilization had the best result for the dose of N30-60. For this dose the results were the best as compared to the unfertilized variant and the average variants. We retain the statistical evidence of this favorable effect obtained by using N30-60 fertilizer as compared to the witness N0 and the reduced effect we obtained when using variants with bigger doses N90-120 kg/ha. We had the same situation when we compared the poor crop of the un-irrigated field with the better one of the irrigate field where the differences are very significant.>
The effect of different nitrogen doses applied in close connection with the bacterization and in the conditions of humidity conducted into the soil, during the whole experimental cycle, contributes to the improvement of the production up to the dose of N60. The further growth of the nitrogen dose up to 90-120 kg/ha leads to a decline with relatively low differences and an obvious lack of the bacterization contribution, especially on an un-irrigated field.>
The average bacterization effect as compared to the other two factors mediated, nitrogen and irrigation, is 110%, with low variances from one year to another. The bacterization, made on the background mediated by nitrogen, leads to the highest level of production for the experimental cycle (2.438t/ha), in the conditions of irrigation.>
In the bilateral combination, nitrogen fertilization and bacterization, we get the best association for the variants N30+bacterization and N60+bacterization. The production change at the interaction of the two factors is sustained by indexes of statistical assurance. The production evolution is situated on a biological curve when the nitrogen dose is N60 and it is combined with the bacterization, growing continuously in accordance with the nitrogen dose. From the economical point of view, it is not justified to double the nitrogen dose (from 60 to 120kg/ha) and give up bacterization, because the production growth is only 4.4%.>
The number of nodosities determined, both total and active, grows during the vegetative stages, their maximum value being in the stage R4, in the beginning of the pods formation. The nodosities decrease numerically in weight. In the stage R2, the nodosities distribution is initially on the main root, and during the following stages on the secondary root formations. According to the data, the overestimated nitrogen doses, as compared to N60, prevent the symbiosis process, existing an obvious numerical decrease of the nodosities, of the weight and of the active state.>
The results obtained during the period studied offer us enough evidence of the usefulness of irrigation, seeds bacterization with Biotrofin (10l/ha) and proportioning the nitrogen doses on the background of these factors in order to get physical and economical productions of seeding garden bean.
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