Date of Award

1963

Degree Type

Thesis

Degree Name

Master of Science in Agronomy

Department

Agronomy

First Advisor

C. Richard Skogley

Abstract

This thesis covers field, greenhouse and laboratory studies that were conducted to determine the effect of various soil phosphorus levels on the herbicidal properties of calcium and copper arsenates. These studies were conducted during 1961 and 1962.

The greenhouse study involved work with annual bluegrass (Poa annua L.) and crabgrass (Digitaria ischaemum Schreb.) grown on two soil types. Levels of soil phosphorus were adjusted to low, medium and high for each soil type and copper and calcium arsenates each at two rates were added to each soil. It was found that the low rate of calcium arsenate was as effective in controlling crabgrass and annual bluegrass as were the other treatments. Soil types and phosphorus levels did not affect the degree of arsenic injury.

The purpose of the field test was to determine the response of annual bluegrass (Poa ~.L.), colonial bentgrass (Agrostis tenuis Sibth.), red fescue (Festuca rubra L.), Kentucky bluegrass (~ pratensis L.) and smooth crabgrass (Digitaria ischae:rm.un Sehreb.) to a single conventional rate of calcium arsenate under two levels of soil phosphorus. Each plot was (a) seeded and treated with arsenic the same day, (b) seeded three weeks after arsenic treatment and (c) seeded six weeks after the arsenic application. The high phosphorus level generally promoted better cover and growth than the low phosphorus level but did not effect arsenic activity in any measured way. Arsenic significantly reduced germination, rate of establishment and growth in height.

Chemical analyses of plant tops and roots showed that soil phosphorus level did not affect uptake of arsenate or movement of arsenate in the soil.

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