Influence of Environmental Factors on Algae in Rice-Field Soil from the Iraqi Marshes PDF

Keywords

algae, rice field, nitrogen

Abstract

A study is reported of the algae in one sample of rice field soil from the Iraqi marshes. 43 taxa were revealed by enrichment culture techniques as opposed to II by direct microscopy. Microcoleus cluhonoplas/es and Nos/oc muscorum were the dominants in the field, but the latter was more successful in laboratory culture (which was carried out only under fully aerobic conditions). The effects of temperature, nitrogen source, phosphate and NaCI were tested. Substantial growth occurred al 45°C, but all algae cultured at 48°C eventually died. Species which were heterocystous and therefore presumed nitrogen-fixers were an important component of the algae crop in the field and dominated laboratory cultures lacking combined nitrogen. 6 taxa showed good growth in medium enriched with 0.5 M NaCl; 3 taxa grew in I M NaCl, but growth was very slow. It is suggested that field research on these algae might indicate ways of modifying cultivation practices to increase the nitrogen status of the soil without the need for introducing nitrogenous fertilizers to this region.