2008 Joint Annual Meeting (5-9 Oct. 2008): Are Soil Microbial Community Composition and Soil Microbial Potassium in Glyphosate Treated No-till Soils Linked to Corn Potassium Deficiency?.

Our study analyzes Glyphosate treated no-till soils with main emphasis on upland non-potassium (K) deficient corn sites and lowland sites that have a history of corn K deficiency. Corn K deficiency at lowland sites occurred although soil K test values were adequate for corn nutrition (> 150 mg kg^-1). Our hypothesis is that potassium deficiency of corn is linked to a microbial immobilization of soil K whereas soil fungi might play an important role in potassium immobilization. There is evidence that fungi are more abundant in Glyphosate treated soils and that fungi have a high potential to incorporate K in their biomass.

Soil samples have been collected in winter, spring, and twice in summer during corn growth. We measured different soil K pools: Non-exchangeable, exchangeable, and microbial K. We also analyzed soil microbial community composition using a microbial fatty acid profiling method.

We have seen that certain K-deficient sites at lowland positions became fungal dominated and have high microbial K values during the early corn growing season which might explain the K deficiency of the corn. Other sites revealed no differences in soil microbial properties between K-deficient and non-deficient corn sites. Thus, soil mineralogy will be analyzed which might help to understand corn K deficiency.