Document Type

Thesis - University Access Only

Award Date

2007

Degree Name

Master of Science (MS)

Department / School

Plant Science

Abstract

Producers are facing complex issues in agricultural production today. Quantity and quality of water are major concerns throughout the world. With increased concern about aquifer depletion and use of irrigation water in the US, available water should not be wasted. In addition, there is increasing pressure to reduce the amount of agricultural herbicides to our agricultural land. Reducing herbicide use will reduce offsite pollution in water and non-target areas. Are we applying more herbicides than needed to maximize yields? Are there places where we can cut the use? In 2000 and 2001, this study investigated the relationship of weeds and water on crop yield and weed biomass at several eastern South Dakota locations. Four locations in eastern South Dakota were used to examine weed, water and landscape interactions in com and soybean production. The South Dakota State University research farms at Beresford and Brookings, SD that had 0-2% slope were used to investigate the two-way interactions of water (dryland vs. irrigated) and weeds (weedy vs. weed-free). Two fields that had topographic features of summit and foot slope were used to investigate landscape position relationships with the effects of weeds and water on weed biomass, and grain yield and plant residue of com and soybeans. Irrigated areas received about double the natural rainfall to insure that water was not limiting. At the Beresford location in 2000 and 2001, and Brookings in 2001, soybean yield and plant residue were both reduced by an average of 65% and 39% by weed interference, respectively. Additions of water to the treatments did not significantly improve soybean yield or plant residue in any of the study years at Beresford or Brookings. Com yield and plant residue reduce by weeds and water in all of the study years. Com grain yield and plant residue were reduced by an average of23% and 19%, respectfully, in dryland treatments over the four site years studied in 2000 and 2001 for Beresford and Brookings. The same studies revealed that weeds reduced grain yields and plant residue by 41 and 42%, respectively. Weed biomass was about 18% less on average in non-watered vs. watered treatments. Landscape position influenced biomass production. Water stress reduced grain yields in upper backslope positions.

Library of Congress Subject Headings

Corn -- Yields

Soybean -- Yields

Weeds -- Control

Plants -- Water requirements

Format

application/pdf

Number of Pages

76

Publisher

South Dakota State University

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