Abstract: Culturing an alga with known flocculant production capability on the soil for the purposes of aggregating soil particles is disclosed. According to the disclosure, flocculant producing algae are known in liquid culture medium as disclosed in pending application Ser. No. 421,527 filed Dec. 4, 1973. The nitrogen in the culture medium is maintained so that cellular nitrogen does not fall below 10%. The algae are then inoculated onto soil which is provided with supplemental nutrients and moisture sufficient to produce a multiplication on the order of several hundred fold. The nutrients other than nitrogen are provided in sufficient quantity to permit a further period of growth during which algal flocculants are produced which have the property of binding soil particles into workable aggregates.

Abstract: Cultivation of algae to produce long chain polymers having flocculating properties is disclosed. Algae are cultivated in an aqueous nutrient medium until relatively high culture densities are achieved and thereafter under conditions in which the cells become deficient in nitrogen thereby causing the cells to shift from a growth phase in which protein production predominates to a growth phase in which extracellular polymer production predominates. An adequate supply of other nutrients as well as CO.sub.2 and light are maintained in the culture medium during the latter phase to insure that a change in cell metabolism is produced by a deficiency in nitrogen. The algae then produce high molecular weight polymers exhibiting strong flocculating activity.