Effect of long-term irrigation on stony soils of the Canterhury Plains

Abstract Five unirrigated sites on Lismore soils were sampled in 1945. The same sites, four of which had been irrigated for 25 years and one which had remained unirrigated, and an additional site irrigated for 33 years, were sampled in 1971. Irrigation and fertiliser had caused increases in organic matter and its elemental con stituents, and in exchangeable calcium, pH, and cation-exchange capacity. The effects of irrigation plus fertiliser were greater than the effects of fertiliser alone. Irrigation also affected the distribution of exchangeable magnesium and potassium in the soil profiles. Profile descriptions of the six soils recorded in 1972 showed no notable morphological differences due to irrigation.