FIELD-EVALUATION OF METHODS OF INCORPORATING SOIL CONDITIONERS

A comparison was made of three methods of applying soluble anionic polymers to improve the structure of field soils: spraying and rototilling, spraying and mixing, and application through a drip irrigation system. Structural state improvement was determined in terms of changes in aggregate stability to water obtained from wet sieving. It was found that the most efficient method of adding soluble conditioners in the field was by irrigation. Conditioning by drip irrigation increased the mean diameter of water stable aggregates in the wetting zone around the drippers where highest root densities are found. Mixing soil and conditioner in a concrete mixer was effective in improving soil structure but was tedious. Application of this method was found suitable for conditioning of limited amounts of soil, and could be considered only for small operations. Repeated spraying followed by rototilling was found to be the least effective in terms of soil structure improvement. This method was also much less convenient and more complicated than application by irrigation.