Soil microbial response to nitrogen fertilizer and tillage in barley and corn

It is hypothesized that inorganic nitrogen fertilization rates may affect soil microorganism amounts and diversity. This study examined the differences in soil microbial mass, functional diversity, and community level physiological profiles (CLPPs) of microorganisms obtained from soils treated with recommended (agronomic) inorganic nitrogen fertilization rates and excess inorganic nitrogen fertilization rates under conventional tillage and no-till treatments from 2004-2006. Barley (Hordeum vulgare L.) in a Black Chernozem soil and maize (Zea mays L.) in a Orthic Gleysol were used. Nitrogen applied at recommended rates increased or did not effect soil microbial mass and diversity, but increased fertilization rates lowered biomass. No-till practices in maize resulted in 30-102% increases in biomass. These results support the claim that application rate of inorganic nitrogen can impact soil microflora and soil fertility testing is necessary to avoid any negative impacts on soil microorganisms.