EFFECTS OF MANURE AND MINERAL FERTILIZER APPLICATION ON CRUDE PROTEIN CONTENT OF LUCERNE (MEDICAGO SATIVA L.)
Effects of mineral and manure fertilization on crude protein content of lucerne (Medicago sativa L.) was studied in field trial carried out at the Institute of Forage Crops, Pleven, Bulgaria. The doses of 70, 140 and 210 kg N ha-1 were tested. Ammonium nitrate and well rotted cattle manure were used. It was found that the both types of fertilizers had strong influence on the crude protein yield in the first year of development of lucerne – for mineral fertilization from 15.6 to 31.6%, and for manure – from 33.4 to 47.0% compared with unfertilized control. With increasing age of sward the effect of fertilization significantly decreased, for mineral one. Manure had positive effect on crude protein yield during the whole experimental period. An average mineral nitrogen fertilization at the doses of 70 and 140 kg N ha-1 increased crude protein yield by 4.4 and 6.6%, while manure fertilization at the doses of three levels (70, 140 and 210 kg N ha-1 ) enhanced protein amount from 13.6 to 16.3%. Regardless their nitrogen fixing ability, lucerne utilizes soil or fertilizer nitrogen in the initial development, since nitrogen assimilation required lower rates of ??2 and energy, than for nitrogen fixation. This gives an impact on the crude protein yield from plants. In the following years the role of biological nitrogen increases gradually, enhancing the process of demineralization thereby the nitrogen fertilization has less influence on the synthesis of nitrogen compounds.