Date of Graduation

12-2016

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Trenton L. Roberts

Committee Member

Edward Gbur

Second Committee Member

David Miller

Third Committee Member

Jeremy Ross

Keywords

Biological sciences, Arkansas, Cover crops, Nitrogen credits

Abstract

Soybean farmers in Arkansas need best management practices (BMPs) that maximize the benefits of using cover crops including planting date and fertilization recommendations. An evaluation of cover crop species, planting dates, seeding rates, fertilizer rates, and N accumulation aids in providing these BMPs. The first objective of this research is to assess the effect of planting date on biomass production, as well as looking at the interaction of seeding rate or fertilizer rate for legumes or non-legumes, respectively, using Austrian winter pea (Pisum sativum), cereal rye (Secale cereale), black oats (Avena strigosa), wheat (Triticum aestivum), and tillage radish (Raphanus sativus). Crops were planted on five dates in three locations across the primary crop production regions of Arkansas, using either variable Agrotain-treated urea rates or variable seeding rates. Agrotain is a N fertilizer additive that inhibits urease activity and limits ammonia volatilization loss potential. A 0.9 x 0.9 m sample of above-ground biomass was oven-dried and weighed to determine total cover crop biomass production. This research found that earlier planting dates were preferable for all species and that fertilizer or seeding rates did not have much effect on establishment and biomass across all planting dates.

The second objective was to gauge the potential N credits by assessing the N accumulation via biological N fixation of three legumes in two locations. Three species were evaluated and compared for N accumulation at termination – Austrian winter pea, hairy vetch (Vicia villosa) and crimson clover (Trifolium incarnatum). Pea biomass was taken from the above study, and pea, vetch, and clover biomasses were taken from an herbicide tolerance study. A 0.9x0.9 meter sample of above-ground biomass was oven-dried, ground, and analyzed for total N. This study found that Austrian winter pea generated more biomass on average, and accumulated the most N.

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