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Document Type

Thesis - University Access Only

Award Date


Degree Name

Master of Science (MS)

Department / School

Plant Science

First Advisor

C. Gregg Carlson


Combines equipped with yield monitors are being used to collect on-farm data. The accuracy of this information is in question. The objective of this research was to use yield monitor data to validate a variable rate seeding recommendation, and determined the economic feasibility of variable rate seeding for corn and soybeans. Yield monitor protocols were determined by comparing corn (Zea mays) handharvested and yield monitor data collected from 2 South Dakota corn fields. Analysis of variance (ANOVA) determined the yield monitor and hand-harvested yields were similar when the data was aggregated into plots 86 m long. On-farm research and yield monitor data was then used to validate two variable rate corn seeding recommendation at Webster, Winner, and Beresford, SD, and compare site-specific plant populations against the producer’s uniform plant populations at the same locations as well as Bruce, SD. At each site, five plant populations were planted in strips running perpendicular the field variability. Using yield monitor data, economic optimum plant populations were calculated at four landscape positions. Profitability due to variable rate recommendations increased with said variability. This result suggests site-specific plant populations depend upon soil and climate variability. The economic optimum populations were calculated using two plant population models at four landscape positions. Each population model was developed using separate data sets. At Webster, SD the second equation calculated recommendations similar to the economic optimum seeding rates, while at Winner the first equation was most accurate. These results suggest different recommendations should be used in different corn growing conditions. Similar studies using soybeans were performed at Hayti, SD and Beresford, SD in 2012 and 2013. Soybean plant populations were found to have no impact on yield at Hayti, SD in 2012. At Beresford the 432,750 seed/ha rate yielded higher than the other populations. Soybean variable rate plant populations at four landscapes followed a trend opposite of corn; however soybean grain yield did not vary based upon landscape position. This suggests variable rate seeding in soybeans can reduce cost; however yield benefits from the practice might be limited.

Library of Congress Subject Headings

Corn -- Sowing -- South Dakota
Corn -- Yields -- South Dakota
Soybean -- Sowing -- South Dakota
Soybean -- Yields -- South Dakota


Includes bibliographical references (pages 111-112)



Number of Pages



South Dakota State University


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