Stability of soil structure for water movement in an aridisol

Graduation date: 1989Lack of stability of soil aggregates for water\ud movement is a major problem in arid soils due to low\ud organic matter and higher sodium contents. Soil\ud amendments for improving stability of structure and\ud increasing infiltration of water are essential to solve\ud water management problems in these areas.\ud Different rates of two amendments, gypsum and\ud polyacrylamide, were applied to determine the optimum\ud rate needed for maximum increase in infiltration of water\ud into soil columns under laboratory conditions. The\ud structural stability of soil samples taken from an\ud experimental area at the Malheur Experiment Station,\ud Ontario, Oregon was characterized by a wet sieving\ud method.\ud It was found that gypsum salt applied at the rate of\ud 25 tonnes/ha increased the infiltration. The wetting\ud front of saturated and half saturated gypsum solutions\ud moved faster into soil columns than that of water. The\ud effect was due to replacing sodium from exchange sites\ud by calcium ions. The saturated gypsum solution had\ud equivalents of calcium that were more than double the\ud total number of equivalents of exchangeable sodium in the\ud entire soil column.\ud Polyacrylamide (PAM) solution applied at 7.5, 15,\ud and 30 ppm concentration to soil columns did not increase\ud the rate of infiltration over the check. This was\ud apparently due to the adsorption of PAM on soil\ud particles. However, the wetting front of water moved\ud faster in PAM treated aggregates than in the check\ud without PAM treatment. The PAM was mixed with soil at\ud rates of 120 and 240 ppm by weight and aggregates were\ud made by pressing the PAM treated soil through a 2 mm\ud sieve. The columns were packed with these air-dried\ud aggregates. Furthermore, it was found that stability of\ud PAM treated aggregates was significantly higher than of\ud the untreated aggregates.\ud The data analysis of the samples taken from a field\ud trial at Malheur Experiment Station indicates that both\ud gypsum and PAM increased the stability of soil structure\ud over the check