H.—34,

The Kaharoa soils cover the western part of the Bay of Plenty and extend south to the Mamaku Plateau. Farther to the south and east they reappear from beneath the Tarawera ash in the neighbourhood of Galatea and To Whaiti. Three main divisions are recognizcd —viz., the scrub soils, the slightly more leached soils under bush, and those in which a grey A 2 layer is developed under the heavier rainfall on the Mamaku Plateau. All the Kaharoa group have medium sand topsoils and gravelly subsoils, and hence are inclined to be droughty. They are most fertile where the ash is thinnest and the gravelly subsoil least developed, as 011 the shores of the Bay of Plenty. The Taupo soils cover a much larger area, extending from Putaruru in the north to the neighbourhood of Napier in the south, and from Taumarunui in the west to the summit of the ranges north-east of Gisborne. Older Taupo showers extend still farther to the north-east. As with the Kaharoa, three main stages are recognized—viz., the immature soils of the scrub and tussock country, the browner soils of the forest zone, and the mature soils of the wetter uplands where the profiles show both a leached A 2 horizon and in places a well-developed humus pan. The Podsolic Soils from the Sedimentary Rocks.- -These are well developed north of Auckland, in the neighbourhood of Wellington and parts of southern Wairarapa, and on the very extensive areas of hill country from which the later showers of volcanic ash have been eroded and where the rainfall is over 60 in. Young podsolic soils on recent sand-dunes lixed by vegetation are developed extensively on the west coast. The largest area is in the Manawatu, where the soils carry a good mixed pasture. The subsoil is loose and overdrained. Closely-related soils on sandhills fixed by weathering occur near the west coast from Raglan northwards. These fertile soils are slightly acid and are well supplied with bases. The subsoil is loamy, and hence they retain the moisture well. Young and immature podsolic soils derived from calcareous sandy inudstone are best developed in the King-country and in the Gisborne area, where the rainfall is more than 60 in. per annum. These fertile soils are neutral or slightly acid and are well supplied with bases. Immature podsols derived from sandstone and greywacke cover relatively large areas, especially in North and South Auckland. These soils, which have developed under a forest cover, are normally clay loams in texture with brown clay subsoils. The topsoils are moderately acid and have a moderate supply of bases. Hence they need top-dressing with lime as well as phosphates. The subsoils are strongly acid and are poorly supplied with bases, consequently even moderate sheet-erosion on hilly land greatly reduces the general fertility. Heavy grey and brown flecked clays representing the semi-mature stage of podsolization are well developed in North Auckland. They are markedly acid and fairly low in bases. Because of their heavy texture and high base exchange capacity these soils improve but slowly. For pasture they need heavy dressings of lime and phosphate. The mature soils (gum lands) are practically confined to North Auckland. These have welldeveloped posdol profiles with strong grey A 2 horizons. They are strongly acid and well leached of bases. Owing to their low capacity, pasture responds well to lime and phosphates where the topsoil is loamy. Where, however, the topsoil is a sand and pans are well developed, even heavy top-dressing does not greatly improve the fertility because of the wide fluctuations in soil moisture. The podsolic soils derived from acid igneous rocks occur on the eastern side of the Coromandel Peninsula and scattered throughout the North Auckland Peninsula. Although immature soils are found, most of them arc semi-mature and mature. They closely resemble the soils from the sedimentary rocks described above. The Brown Loams. The brown loams are in three main sub-groups—viz., the yellow-brown loams derived from andesitic volcanic ash, the brown granular clays derived from andesite and dolerite rocks, and the red-brown loams derived from basalt. All the brown loams are characterized by a low silica/sesquioxide ratio, and show marked powers of phosphate fixation. The Yellow-brown Loams.—The yellow-brown loams are developed in fine-textured ash of andesitic and rhyolitic composition which formerly covered the North Island from near Wanganui and Napier in the south to Auckland in the north. In the central part they are overlain by later volcanic ashes which do not give rise to yellow-brown loams. The yellow-brown loams are all friable soils with a fine granular to " fluffy " structure ; the soil clay is high in alumina and moderately high in iron. Stretching from the Northern King-country to the Waikato River mouth are free silt loams derived from the Mairoa ash of mixed andesitic and rhyolitic composition. On the scrub and fern-covered lowlands, where the rainfall is less than 60 in., the soils are but slightly acid and moderately saturated with bases. They respond well to phosphate top-dressing. Where the rainfall is heavier (60 in. to 80 in.) and the cover is forest, subsoils are more compact. On the wetter uplands (rainfall over 80 in.) the soils are markedly leached of bases with faint A 2 layers in the profile and in places thin iron pans. To the east of the Mairoa ash, in the Tirau, Waihi, and Tauranga districts, ash beds lighter in texture and more rhyolitic in composition mantle the surface. The Tirau sandy loam and its finer counterpart in the Morrinsville district are developed under a moderate rainfall. They respond well to phosphate. The Tauranga-Waihi soils are coarser in texture and they show well the progressive stages of leaching. The least leached are the black coastal soils and the brown sandy loams of the rolling a-nd moderately-steep hills, formerly covered with mixed bush. On the Waihi plains and the foothills south of Katikati the soils are more leached and respond to phosphate and potash top-dressing. A similar series of soils covers the rolling and moderately steep land in the eastern Bay of Plenty, East Cape, and northern Gisborne districts.

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