Effect of Mineral Fertilization and Manure on Some Characteristics in Alfalfa (Medicago sativa L.)

Field trial was carried out at the Institute of Forage Crops, Pleven, Bulgaria (2000-2003) to study the effect of mineral fertilization and manure on nitrate reductase activity, plastid pigments content and dry root mass in alfalfa. The experiment was carried out on slightly leached chernozem soil subtype and no irrigation. Mineral fertilizer (ammonium nitrate) and manure (well rotted cattle manure) at the doses of 70, 140 and 210 kg N ha were applied. A tendency for increase of nitrate reductase activity in leaves compared to unfertilzed 1 control and decrease in roots regardless of dose for the both type of fertilizers was found. By increasing the dose of mineral fertilizer nitrate reductase activity in leaves and stems decreased and when manure was applied the values were similar. Mineral fertilizer and manure decreased the total chlorophyll content (chlorophyll a+b) and the decrease was less at high doses. Content of carotenoids increased for all treatments. Dry root mass formed after manure fertilization was from 25.2 to 51.7% greater than that after mineral.