Masters Theses

Date of Award

5-2022

Degree Type

Thesis

Degree Name

Master of Science

Major

Environmental and Soil Sciences

Major Professor

Dr. Forbes Walker

Committee Members

Drs. Nutifafa Adotey, Debasish Saha, and Sean Schaeffer

Abstract

Healthy soils are critical for optimized yields and sustainability in agriculture. Soil health testing can provide valuable information on how management practices are affecting soil health. In west Tennessee, existing soil health tests were unable to discern between significant differences in management practices. A new soil health test called microBIOMETER® has been developed by Prolific Earth Sciences® (Montgomery, NY). MicroBIOMETER® utilizes a new methodology for estimating microbial biomass and uses that estimate as a soil health score. This test has not been validated for use in west Tennessee. This research was focused on the validation of microBIOMETER® in a continuous cotton crop on a Lexington silt-loam at the West Tennessee Research and Education Center (WTREC) in Jackson, TN. The continuous cotton experiment at WTREC has undergone the same tillage, cover crop, and nitrogen fertilization treatments since 1981. Tillage treatments are conventional tillage and no-till. Cover crop treatments are no cover crop, hairy vetch (Vicia villosa), crimson clover (Trifolium incarnatum), and winter wheat (Triticum aestivum). Nitrogen application rates are 0, 34, 67, and 101 kg N / ha. Treatments present significant differences in management practices. It is expected that a functional soil health test can distinguish between these treatments. Three sets of samples were taken at WTREC and tested with microBIOMETER®, substrate induced respiration (SIR), and chloroform fumigation extraction (CFE). CFE and SIR are two lab standard methods for estimating microbial biomass and were included as comparisons for microBIOMETER®’s estimate of microbial biomass. Environmental conditions were analyzed to isolate impacts of management treatments. Environmental conditions may have had a role in observed temporal variability of microbial biomass but did not appear to impact scores within an individual sample. Temporal variability may also have been impacted by cotton growth stages. CFE and SIR were able to consistently distinguish between management treatments, but differences were not significant. MicroBIOMETER® was unable to consistently distinguish between treatments. MicroBIOMETER® estimates of microbial biomass were more variable and less reliable than SIR or CFE estimations. It is not recommended that microBIOMETER® be used as a stand-alone soil health test in the conditions tested in this research.

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