Effect of mineral and organic fertilization of alfalfa on some seed yield characteristics, root biomass accumulation and soil humus content

Abstract

A field trial at the Institute of Forage Crops, Pleven, Bulgaria (2000-2003) was conducted to study the effect of mineral and organic fertilization on seed yield of alfalfa, root biomass accumulation and soil humus content. Alfalfa variety 'Victoria' was grown on a leached chernozem soil without irrigation. Rates of 70, 140 and 210 kg ha^-1 mineral nitrogen (active ingredient) were tested as ammonium nitrate and well-matured cattle manure. It was found that mineral and manure fertilization at 140 and 210 kg ha^-1 increased seed yield by 9.9% and 20.9% for mineral, and by 30.3% and 40.6% for manure. Seed yield was more stable under manure fertilization compared with mineral fertilization. Alfalfa accumulated between 2669 and 3098 kg ha^-1 dry root mass after mineral fertilization and between 3310 and 3570 kg ha^-1 after manure application. Additional root mass of 482 to 698 kg ha^-1 was found to be accumulated for manure treatments compared to mineral fertilization. High ratios of nitrogen yields (192 - 216 kg ha^-1) and plant available nitrogen (77 - 86 kg ha^-1) have been obtained from the treatments with manure. The highest amount of humus remained in the soil after fertilization of alfalfa with manure at the rate of 210 kg ha^-1.