Document Type

Thesis - Open Access

Award Date

2018

Degree Name

Master of Science (MS)

Department / School

Agronomy, Horticulture, and Plant Science

First Advisor

Sharon A. Clay

Keywords

abrasive grit management, nitrogen, organic cropping systems, weed Science

Abstract

Weeds are one of the biggest challenges for organic growers because of the alternative weed control methods. Air-propelled abrasive grit management has been reported to control weed seedlings in corn and soybeans while maintaining yield. This research examined the weed control, corn and soybean yields, nitrogen mineralization, and nitrogen yield responses from grits. The grits used in this research included: Phytaboost Plant Food 7-1-2 (soybean meal), Sustane 8-2-4 and 4-6-4 (turkey litters), and two non-fertilizer grits: Agra Grit (walnut shells) and corn cob meal. Field studies were conducted from 2015 to 2017 in Aurora, SD, Beresford, SD and Morris, MN. Nitrogen mineralization and total nitrogen release from selected grits in two different soils were evaluated in 100 d incubations. The response of corn, wheat, red russian kale and velvetleaf to Sustane 8-2-4, Agra Grit and corn cob meal amended soil was investigated. Agra Grit consistently reduced in-row broadleaf weed biomass in all four site years, whereas when grass weeds were dominant, in-row weed biomass was not reduced with two grit applications. When grit treatments reduced in-row weed density, corn yield increased with fertilizer grits higher than the weed-free check. In-row weed biomass in soybeans was similar among treatments, but when total weed biomass was reduced, the soybean yields were 31 to 55% greater in the grit treatments than weedy checks. Organic fertilizer grits increased soil available nitrogen with 50 to 70% of nitrogen mineralized. Non-fertilizer grits immobilized soil available nitrogen. Plant height and dry weight of wheat, red russian kale, and velvetleaf were greater when the soil was amended with Sustane 8-2-4 compared with Agra Grit, corn cob meal, and no-grit control, although fresh weights and relative greenness were similar among treatments. The use of organic fertilizer grits provide a source for nitrogen for all plants in the targeted area, whereas non-fertilizer grits may immobilize nitrogen. Corn and soybean yields can be increased when two applications of air-propelled grits reduce weed density, regardless the type. Grits may provide nitrogen for the crop but weed control is critical as additional nitrogen also may stimulate weed growth.

Library of Congress Subject Headings

Weeds -- Control.
Organic farming.
Nitrogen.

Description

Includes bibliographical references (pages 151-178)

Format

application/pdf

Number of Pages

210

Publisher

South Dakota State University

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Rights Statement

In Copyright