Irrigation investigations in Otago, New Zealand: VIII. Physical properties of soils of the Lower Waitaki Plains

Terrace soils of the Lower Waitaki Plains have a high volume of stones, ranging from 17.5% to 61.2% by volume over the 0.24 in. depth. Although these soils are silt loarns, with a high percentage of organic carbon, the moisture-holding capacity is considerably reduced by the volume of stones. The average available moisture for the 0-12 in. depth is 1.95 in., considerably lower than that of similar soil groups studied in this series of investigations. Soils of the downlands are stone-free and have an average available moisture of 2.81 in. for the 0-12 in. depth. Some of the soils studied have low macroporosity values in the depths below 4 in. Any tendency for the macroporosity to decrease after irrigation could result in increased drainage problems.