Document Type

Thesis - Open Access

Award Date

2016

Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

Peter Sexton

Keywords

corn, fertilizer, nitrogen, no-till, South Dakota, tillage

Abstract

Nitrogen (N) is a vital factor of corn (Zea mays) production. Previous work in South Dakota has shown that there is uncertainty as to whether nitrogen requirements are the same for corn raised under no-till (NT) versus conventional till (CT) production systems. The objective of this study was to evaluate whether N requirements continue to be greater under long-term NT versus CT production systems in southeastern South Dakota, while also considering effects from cover crops and crop rotation. This was a two year study conducted at the SDSU Southeast Research Farm near Beresford, SD; it was superimposed on a long-term rotation and tillage study established in 1991. Treatments included applied N rates of 0, 40, 80, 120, 160, and 200 lbs N acre-1. Rotations were: corn/soybean (Glycine max) and corn/soybean/small grain; the three-year rotation was split additionally by ‘cover crop’ and ‘no cover crop’ treatments. Parameters measured included: soil plant analysis development (SPAD) chlorophyll readings, normalized difference vegetation index (NDVI) readings, ear leaf N content, total plant N uptake, yield, test weight, moisture, and grain protein. In 2014 small plot results were quite variable due to 13.5” of rainfall in June; the 2015 growing season was mild, producing more representative yields. Both N rate and tillage showed significant impacts on yield in the 2014 and 2015 three-year rotation. In 2014, spring soil nitrate levels tended to be 50 lbs ac-1 less in the ‘cover crop’ verses ‘no cover crop’ treatments, but there were no significant yield differences between cover crop treatments. Nitrogen that was not available in the spring likely became available later when cover crop residue decomposed. No-till corn was generally more sensitive to N application in the 2015 two-year rotation than CT corn, however, optimum N rates were the same across tillage regimes. In this study, long-term NT soils did not consistently require more N than CT soils. More research needs to be conducted to further define N recommendations and the impact of cover crops and crop rotation on soil N credits.

Library of Congress Subject Headings

Corn -- Fertilizers -- South Dakota

Nitrogen fertilizers -- South Dakota

Tillage -- South Dakota

Crop rotation -- South Dakota

Cover crops -- South Dakota

Crops and nitrogen -- South Dakota

Description

Includes bibliographical references (pages 123-135)

Format

application/pdf

Number of Pages

152

Publisher

South Dakota State University

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Rights Statement

In Copyright