Degree Type

Creative Component

Semester of Graduation

Fall 2020

Department

Agronomy

First Major Professor

Mike Castellano

Degree(s)

Master of Science (MS)

Major(s)

Agronomy

Abstract

One of the biggest challenges with soil nitrate (NO3-) testing to help manage nitrogen fertilizer inputs is time. There is too much time between pulling soil samples, testing each soil sample, and waiting for receipt of the test results from a laboratory. Growers need data faster so they can better manage nitrogen fertilizer inputs. This study tested for correlations among soil NO3- measurements with two different measurement methods across three nitrogen fertilizer rates. The two measurement methods included the 360 SOILSCAN, which measured soil NO3- in the field without laboratory processing and conventional laboratory-based soil NO3- measurements. It is important to note that due to different measurement methods the 360 SOILSCAN and conventional laboratory measurements could produce different absolute measurements of soil NO3- that are well correlated with each other and yield response to nitrogen fertilizer. This is important because there is no ‘correct’ measurement of soil NO3-; rather the measure of a good soil fertility test is correlation with yield response to nutrient input. The 360 SOILSCAN measures a wet soil sample that is mixed with deionized water within minutes of pulling the sample. In contrast, laboratories typically require more than 24 hours after receiving a sample to provide results. Conventional soil labs air dry soil and grind soil before mixing the soil with a strong salt solution to extract NO3-. Hence, it is expected that the magnitude of soil NO3- measurements will differ between the two methods. Yet, we are unaware if the two methods are correlated. The conventional soil lab, KSI had a much boarder range compared to the 360 SOILSCAN. It seemed the 360 SOILSCAN results were consistently lower than the KSI results. Correlations between the two methods were poor within nitrogen fertilizer rate treatments (zero-N control, medium-N, and high-N) and especially at NO3- concentrations that are relevant for management decisions (i.e., XX-XX mg N kg-1 soil). However, looking at the data results across the broad range of nitrogen fertilizers rates, the data were well correlated.

Copyright Owner

Marley, Alexis

File Format

PDF

Embargo Period (admin only)

12-3-2020

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