Growth response of alfalfa to Azomite composite micronutrient fertilizer on four lime-amended Virginia soils

The growth responses of alfalfa (Medicago sativa L.) to azomite, a natural composite earth mineral, were assessed in a greenhouse experiment at Virginia State University, Chesterfield, VA. Alfalfa plants were raised on lime-amended Bojac, Bourne, Emporia and Cullen soils that received 224 kg K/ha in 14 × 16 cm pots. Azomite, a natural composite micronutrients fertilizer, was applied at 0, 200, 400, 600 kg/ha and experiment replicated three times. Over 29 weeks, plant heights and forage biomass were recorded and growth rates calculated at four different cuts. The data were analyzed using the PROC GLIMMIX procedure in SAS 9.3 to test for effects of soil type and azomite rates on the performance of alfalfa. Results indicate that, compared to the control, azomite application increased plant heights, forage biomass and growth rates of alfalfa and more so on Bojac and Bourne than Emporia and Cullen soils. This was most likely due to good water permeability and high nutrient activity in the semi-active Bojac and Bourne compared to the sub-active Emporia and Cullen soils. Plant heights, biomass and growth rates were greatest for plants receiving 200 kg azomite/ha while those on the 600 kg/ha rate performed worse than the control. Alfalfa on lime-amended and K-sufficient soils responded positively to 200 kg azomite/ha, but was impacted negatively at the higher rates.