Population Dynamics of Chlamydomonas sajao and Its Influence on Soil Aggregate Stabilization in the Field

Abstract

Chlamydomonas sajao, a single-celled, eucaryotic microalga, was inoculated onto replicated field plots cropped to corn at two rates (5 x 10 and 5 x 10 log-phase cells ha) to assess colonization, reproduction, and persistence, changes in soil carbohydrate content, and wet stability of 0.92- to 1.68-mm-sized aggregates from the surface 2- to 3-mm soil veneer. The most-probable-number technique and extraction and fluorometric quantification of chlorophyll were used as indices of microalgal abundance. Cell numbers ranged up to 6.9 x 10 g of soil by most probable number and were significantly greater on high-rate than on low-rate and control plots over a 10-week period. Chlorophyll content and most probable number were positively correlated (r = 0.64) for the high-rate plots but not for low-rate plots or the controls. Increased wet aggregate stability measurements (33 to 77%) for the high-rate plots during the growing season were significantly greater than for low-rate and control plots, which were not different from each other. The work leads support to the hypothesis that mass-cultured palmelloid microalgae are a feasible means for conditioning soil biologically.