Oxidic Soils [X]
The first grape vines in New Zealand were probably planted on these soils by an associate of Samuel Marsden at Kerikeri in 1817.
Oxidic Soils are clayey soils that have formed as a result of weathering over extensive periods of time in volcanic ash or dark volcanic rock. Despite high clay contents the soils are friable, with low plasticity and fine structure. They contain appreciable amounts of iron and aluminium oxides.
Oxidic Soils are only known in the Auckland and Northland regions. Parent materials are derived from strongly weathered andesite, dolerite or basalt rock or ash. They cover < 1% of New Zealand.
Soils have limited rooting depth, well-developed and relatively stable structure, slow permeability, and moderate or rapid infiltration rates. Clay contents are high, ranging from 50 to 90%. Soil water deficits are common in summer.
Oxidic soils are strongly weathered with low reserves of potassium, magnesium, calcium and phosphorus. Clays have low cation exchange capacity at the natural pH of the soil, and phosphate retention is high.
Soil orders are divided into soil groups based on variation in factors such as drainage status, parent material, chemical and physical properties