Concentrating Fertilizer Under Clumps of Grain Sorghum to Increase Efficiency.

Concentrating fertilizer in the plant root zone generally increases efficiency by reducing nutrient fixation, volatilization, and leaching. Recent studies have also shown that growing grain sorghum (Sorghum bicolor L. Moench) plants in clumps rather than equally spaced is a useful strategy under dryland conditions.  Greenhouse and field studies were conducted for two years to investigate the effect of concentrating application of fertilizer under clumps. The hypothesis was that fertilizer use efficiency would be greater for grain sorghum growing in clumps with fertilizer applied beneath the clumps than for equally spaced plants with fertilizer applied in a band. Plants were grown with two different fertilization methods   concentrating under clumps and applying as a band under equally spaced plants at different rates. Grain, stover, and root samples were analyzed to determine N and P uptake. First year results showed no differences in yield and nutrient contents between the two methods of application but the second year greenhouse study showed higher grain yield for clumps. Equally spaced plants produced more tillers than clumps during vegetative growth in all studies. Preliminary results are not sufficiently consistent to draw conclusions.