Assessing Exchangeable Soil Nitrogen in Cotton Fields from Different Best Management Practices

Undergraduate #54
Discipline: Ecology Environmental and Earth Sciences
Subcategory: Ecology

Raven Lewis - University of Arkansas at Pine Bluff
Co-Author(s): Oluwayinka Iseyemi,Delta Water Management Research Unit, USDA-ARS, Jonesboro, AR; Arlene Adviento-Borbe, Delta Water Management Research Unit, USDA-ARS, Jonesboro, AR

Everyone has heard of the benefits of using N fertilizer on your plants; but did you know that using N fertilizer could be harmful? There are many different types of fertilizers and application methods, some being less harmful than others. Fertilizer becomes harmful when nutrients are found at deeper depths in the soil. This is a problem because the deeper the nutrients are found, the more likely to cause contamination of groundwater. I tested for ammonium, nitrate, and nitrite in the soil of cotton plants at various depths managed under different tillage and fertilizer N management practices. The two furrow tillage treatments (4” standard sweeps cultivator: CT vs. conservation Buffalo plow: FT) and N fertilizer types and placements (Broadcast urea: UR vs. side-dressed 32% UAN: UA) at a rate of 90 lbs acre-1 fertilizer N were arranged in a randomized complete block design with three replications at the Judd Hill Research Farm, Trumann, AR. Across all treatments and sampling dates, soil exchangeable ammonium, nitrate and nitrite ranged from -0.03 to 1.02, 0.07 to 1.67, and -0.009 to 0.10 respectively. Following the application of N fertilizer, concentrations of nitrate increased in the 0-15 and 15-30 cm soil depths in both tillage treatments. Forms and placements of fertilizer N influenced the amounts in different soil depths. Lowest nitrate concentrations were found in deeper depths suggesting a less likely potential to cause nitrate leaching. Our findings suggest that conservation tillage (FT) and side-dressed UAN (UA) reduce potential fertilizer nitrogen losses in cotton production.

Funder Acknowledgement(s): Supported by NSF grant #1348389 to Srivatsan; ABI for space, funds and equipment, funds from Office of Diversity at A-State

Faculty Advisor: Arlene Adviento-Borbe, Arlene.AdvientoBorbe@ARS.USDA.GOV

Role: I was able to collect soil samples, analyze them for ammonium, nitrate, and nitrite, and input the data I received from analyzing the samples into graphs.