COMPARISON OF THE EFFECTS OF LATEX AND POLY(DADMAC) ON STRUCTURAL STABILITY AND STRENGTH OF SOIL AGGREGATES

Two types of high molecular weight polymers having contrasting charge properties and molecular shapes [latex and poly(DADMAC)] were applied at different rates to three Alfisols and a Mollisol to examine the eff ects of these polymers on soil strength and structural stability, and to identify some of the mechanisms by which these polymers act to stab ilize soils. Wet aggregate stability, mechanically dispersible clay, a nd soil friability tests were used to assess treatment effects, which were found to be greatest in soils having a poor structural condition. Each polymer acted differently. Latex, which acted like a coat of pai nt (because of its inability to penetrate beyond the surface of aggreg ates), dramatically increased the proportion of water stable aggregate s >2 mm in all soils examined, and this was achieved without the tradi tional (expensive) use of aromatic oils and stabilizers. The latex coa ting produced a conglomeration of smaller soil aggregates, but did not extensively alter either the dispersibility of the aggregates in the face of mechanical action, or their strength and friability. Results i ndicate latex may be best suited to minimum tillage cropping systems. Poly(DADMAC), by contrast, was capable of entering most pores accessib le to water. This enabled it to minimize clay dispersion, increase soi l friability, and to modestly increase the size of water stable aggreg ates. In many ways, poly(DADMAC) would appear to be an ideal soil cond itioner, although the economic suitability of this polymer and its eff ects on erosion control and plant growth have yet to be assessed.