Nutrient composition of Amaranthus species as affected by nitrogen fertilization and harvest date

Author

Robert D. Walters

Date of Award

8-1985

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant, Soil and Environmental Sciences

Major Professor

David L. Coffey

Abstract

A study was conducted to evaluate the proximate composition, carbohydrate, mineral and nitrate content of selected Amaranthus acces-sions from Latin America, Africa and Asia. The effects of varying levels of nitrogenous fertilizer, accession, and harvest date on these nutrients was assessed and compared. Three rates (0, 150 and 300 kg/ha) of ammonium nitrate were applied to an Etowah silt loam in 198A. Whole leaf tissue samples from six accessions were obtained during the growing season at 25, 35, 45, 55 and 65 days after germination. Grain samples from four accessions were obtained at the end of the growing season. The results from laboratory chemical analyses for proximate composition, carbohydrate, mineral and water soluble NO₃^- concentration were evalu-ated. Differences in plant growth habit in vegetable vs. grain ama-ranths accounted for the divergence observed in crude protein response among accessions. Prolonging the vegetative state in vegetable ama-ranths would likely result in levels of leaf crude protein, and other nutrients, that fluctuate more during the growing season than in the grain types. While amaranths possess several unique nutritional attributes, early harvesting of tender stems and leaves must be done for maximum nutritional and culinary utility. Early leaf harvests typically had high crude protein and K concentrations, and relatively low fiber con-tent. Water soluble NO₃^- concentration was highest during early growth stages, and declined rapidly thereafter. Overall, levels of leaf NO₃^- within two accessions did not exceed 239 mmol/kg dry weight for any of the NH₄NO₃ or harvest date treatments. The proximate and carbohydrate composition of four grain amaranth accessions was not significantly affected by the application of NH₄NO₃. Grain calcium concentration declined in three accessions as a result of the NH₄NO₃ treatments. Significant differences among accessions in grain composition were observed. Split applications of fertilizer, as practiced in other agronomic crops, may prove more satisfactory as a means of enhancing yields and/or nutritional composition of amaranth grain.

Recommended Citation

Walters, Robert D., "Nutrient composition of Amaranthus species as affected by nitrogen fertilization and harvest date. " Master's Thesis, University of Tennessee, 1985.
https://trace.tennessee.edu/utk_gradthes/7423