Doctoral Dissertations

Date of Award

8-1974

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Plant, Soil and Environmental Sciences

Major Professor

Homer D. Swingle

Committee Members

Lloyd F. Seatz, David L. Coffey, Gordon E. Hunt

Abstract

The purpose of this investigation was to determine the effects of rates and sources of nitrogen on growth of Spinacia oleracea L. cultivar Chesapeake and on nitrate-nitrogen content of leaves and soil samples from 0-4 and 4-8-inch depths within the fertilized plots.

One hundred and 200 lbs N/A from ammonium nitrate, calcium nitrate, ammonium sulfate, and sulfur-coated urea was applied in split applications to spring and fall spinach.

Fresh weight of plants was determined at harvest stage and nitrate-nitrogen content of leaves and soil from 0-4 and 4-8-inch zones was determined periodically throughout the study.

Fresh weight of plants was highest when 100 lbs N/A was applied from calcium or ammonium nitrate. Response to nitrogen fertilization as indicated by nitrate-nitrogen content of leaves was negligible in the fall experiment, but much greater in the spring test. Nitrate-nitrogen content of spinach leaves from the fall test was significantly increased at only two of seven sampling dates by application of 200 lbs N/A from ammonium nitrate, calcium nitrate, or sulfur-coated urea. In contrast, increases were found in nitrate-nitrogen content of leaves from spring spinach at almost all sampling dates regardless of the source of nitrogen when 200 lbs N/A was applied.

In the fall study increased nitrate-nitrogen levels were found in soil at the 0-4 and 4-8-inch depths at two of six sampling dates when plots were fertilized with 200 lbs N/A from ammonium nitrate or calcium nitrate.

Large increases in nitrate-nitrogen content were found in 0-4-inch soil profiles in the spring experiment when plots were fertilized with either 100 or 200 lbs N/A from either calcium or ammonium nitrate. Moderate increases in nitrate-nitrogen were also found in 0-4-inch soil profiles from plots fertilized with either 100 or 200 lbs N/A from ammonium sulfate.

Levels of nitrate-nitrogen in the 4-8-inch profiles were increased slightly in the spring experiment when 200 lbs N/A was applied from ammonium nitrate or ammonium sulfate. Greatest increases were observed when 200 lbs N/A was applied from calcium nitrate.

In conclusion these data indicate that applications of 100 lbs N/A from calcium or ammonium nitrate was near the optimum rate for spinach growth under conditions of these experiments and that 200 lbs N/A from ammonium nitrate, calcium nitrate, ammonium sulfate, or sulfur-coated urea may result in excessive levels of nitrate-nitrogen in plant tissue. The data also suggest that application of 200 lbs N/A from calcium nitrate, ammonium nitrate, or ammonium sulfate provide a potential for nitrate-nitrogen buildup in the soil and pollution of groundwater aquifers.

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