Document Type

Thesis - University Access Only

Award Date

2006

Degree Name

Master of Science (MS)

Department / School

Plant Science

Abstract

Corn (Zea mays) yields are limited by a variety of stresses in different environments that are difficult to quantify. The carbon-13 discrimination method has been used to assess and quantify the impact of water and nitrogen stress in corn and wheat. Research was conducted in Aurora in eastern South Dakota in 2004 and 2005 to assess the impact of velvetleaf (Abutilon theophrasti) and shade (2 004) and shade, nitrogen fertilization and irrigation (2 005) on corn grain yields and corn carbon-13 discrimination(􀃫 ). Corn grain and stover samples were analyzed using a Europa 20-20 isotope ratio mass spectrometer to determine􀃫, N%, C% and o 15N. In 2004, the presence of velvetleaf resulted in decreased corn grain yields and increased grain􀃫 values. Based on􀃫 values, the effect of plant competition for resources was attributed to competition for N and light. In 2004 and 2005, shade decreased corn grain yields and increased grain􀃫 values compared to corn under full sunlight. Supplemental water via irrigation in 2005 did not result in significant increases in corn grain yields, but did tend to decrease corn grain 􀃫 values. In the full sunlight treatment in 2005, yields were increased by N fertilizer. However, in the 40% and 60% shaded treatments, yields were not influenced by N fertilizer. These results show that corn yields decreased with increased shade and that grain Li increased with shade. In this C4 plant, water and light stress had similar effects on Li, while N stress had a different influence on Li. There is the possibility for light stress to be assessed in corn using the Carbon-13 discrimination (Li) method as long as water stress is not also present. This new technique may then allow for a better understanding of the conditions of the corn field and enable producers to make adjustments in the following growing seasons.

Library of Congress Subject Headings

Corn -- Effect of stress on

Corn -- Yields

Format

application/pdf

Number of Pages

106

Publisher

South Dakota State University

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