Adubação nitrogenada na produção da alfafa (Medicago sativa L.) e na fixação simbiótica em solos de diferentes origens

Abstract

The research work was accomplished at the Animal Science Department of the University Federal de Lavras - MG - Brazil. The experiment was conduct in greenhouse, " Ana Dias " model, int he forage culture sector. It the was aimed to evaluate the effect of levels of nitrogen fertilization (0, 50, 125, 250 and 450 mg N/dm of soil) in soil native of lacation where it had been and cultivated to alfalfa before and with sowing performed in a inoculated and uninoculated soil. The design employed was a randomized block factorial with 5 levels of nitrogen, 2 origins of soils 2 soils conditions, amounting to a replications. Bromatological analysis of dry matter (DM), crude protein(CP), neutral detergent fiber (NDF), acid detergent fiber (ADF), calcium (Ca) and phosphorus (P) of alfalfa, for further calculations of the yields and contents expressed in g/pots and percentage respectively. The results obtained enabled to find that the use of growing levels of nitrogen fertilization increased the yield of the crops (P<0,05) concerning the accumulation of DM, CP and contents of NDF, ADF, Ca and P, but as to soil origin and soil inoculation, no effect was observed (P>0,05), suggesting an inhibition effect of the application of nitrogen on the biological fixation of this element. It follows that, under the conditions of this experiment, nitrogen fertilization in significantly increases yield and nutritive value with applications of 0 up to 450 mg N/dm3 of soil. Regardless of the soil origin and presence or not of inoculation, the application of370.22 mg N/dm3 of soil is that presents greater efficiency of utilization as for dry matter yield whereas the dose of450 mg N/dm3 of soil presents greater efficiency in a crude protein yield. The origin of soil and inoculation did not affect alfalfa yield since nitrogen fertilization may have inhibited the nitrogen biological fixation, therefore there being the need for a isolate study of those factors. As There was nodulation of the inoculation of the inoculated plants and there was no inoculation effect, it is probable that the strain of Rhizobium utilized (Br7407) has not been the most indicated.