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Control Over Fundamental Soil N Cycling Process in Minnesota Cropping Systems: Nitrification, Nitrosation

Start Date: 2014
Principal Investigator: Michael Sadowsky
Organization: University of Minnesota, Department of Soil, Water, and Climate
Status: Complete

Background Info

This research seeks to understand the fundamental interactions of soil microorganisms with ammonium and with nitrite, in the two-step process of transforming nitrogen from its inorganic to its more highly mobile, mineralized form. Urea was applied at five rates across all the testing sites. Soil samples from eight different Minnesota locations account for the variety of textures from clay to sandy loam, as well as the impact of different cropping systems (corn/beans, corn on corn, and even one continuous soybean) and cultivation methods (conventional, no-till, etc.). In order to fully understand the interaction of soil, fertilizer and microbial communities, researchers are testing soils for carbon and nitrogen content, particle size, pH, ammonium sorption capacity and cation exchange capacity.

Objectives

Determination of the key factors regulating nitrification and nitrite accumulation in Minnesota soils by quantifying inorganic N dynamics and the separate activities of the ammonium-oxidizing microbes (AOMs) and the nitrite-oxidizing microbes (NOMs).

Determination of the key factors regulating the incorporation of NO2– into soil organic matter during nitrification

Determination of the susceptibility of the incorporated N to mineralization

Key Findings

The testing reveals the relative amount of the various forms of nitrogen in the soil, over time. DNA have successfully been extracted from microbes in six of the demonstrations soil, with two more analyses underway. The researchers also used quantitative polymerase chain reaction (PCR) to analyze the samples.

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