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Effects of Ammonium Sulfate and Urea on the Growth of Chlorophycean Algae From Rice Fields¹

ABSTRACT

Algal growth in rice (Oryza sativa L.) fields is often abundant, but the quantitative effect of fertilization on algae is not well-understood. The growth of four unialgal isolates from fertilized rice floodwater, including Bracteacoccus minor, Scenedesmus sp., and two species of Chlamydomonas, was studied in soil water extract enriched with an inorganic algal medium and with N as either urea (CO(NH₂)₂) or ammonium sulfate ((NH₄)₂SO₄). Except for one species of Chlamydomonas, isolates had higher cell counts in urea-enriched cultures. There was no significant difference between the growth of cultures with 25 or 50 mg/liter N as urea added or between those with 25 or 50 mg/liter N as (NH₄)₂SO₄. The maximum biomass of all N-enriched cultures was significantly greater than that of cultures with no N added to the medium. Differences in final biomass among isolates were significant but were not proportional to that observed at earlier stages in the growth curve.

Key Words: Bracteacoccus • Chlamydomonas • Scenedesmus • fertilizer • biomass • chlorophyta • Oryza sativa • rice culture

¹ Research conducted at the University of North Alabama, Florence, AL 35630.

² Former Graduate Assistant and Assistant Professor, respectively, Biology Dep., Univ. of North Alabama. Senior author is currently Graduate Assistant, Agronomy Dep., Univ. of Arkansas, Fayetteville, AR 72701; the second author is Assistant Professor, Saginaw Valley State College, University Center, MI 48710.

Received for publication March 7, 1981.