Effects of Micronutrients on Seed Yield and Yield Components of Alfalfa

Effects of micronutrients [molybdenum (Mo), boron (B), iron (Fe), zinc (Zn), manganese (Mn) and copper (Cu)] on seed yield and yield components (seed yield per unit area, fertile shoots per unit area, number of racemes per shoot, number of pods per raceme, number of seeds per pod and 1000-seed weight) of alfalfa were investigated in the northwest region of China, over two seasons (2003-2004) on a torrifluvent soil and a site of 1720 m altitude. After two years study, it demonstrated that molybdenum and boron were more critical for alfalfa seed production. Molybdenum increased seed yield by 27-47%, the number of racemes per shoot by 38-55%, the number of pods per raceme by 100-133%, the number of seeds per pod by 48-61% and 1000-seed weight by 24%, and boron increased seed yield by 22-35%, fertile shoots per unit area by 17-35%, the number of racemes per shoot by 38-64%, the number of pods per raceme by 100%, the number of seeds per pod by 41-52% and 1000-seed weight by 16%. Iron, manganese, and copper had any effect on yield components, but they had no effect on seed yield. Zinc had no positive effect on seed yield and yield components. Among seed yield components, the number of pods per raceme was the most important factor to determine alfalfa seed yield. Results from this study will be used to recommend further evaluation of molybdenum and boron across a number of environments around the world and as a basis for developing recommendations to the alfalfa seed production industry.