11.—34

The soil is thin and very bouldery on type 35. It is used for grazing, but the excessive number of surface boulders detracts from the value of the land. Pastures parch readily on these shallow soils. Type 36, the semi-mature soil, is more leached than the preceding types, and pastures show a more marked response to lime than on the less-leached brown loam. Types 37 and 38, the submature and mature soils, are the most leached soils of the brown-loam group.' A great part (especially of type 38) is scrub-covered, but patches of the original forest cover still remain. On flattish areas the soils and subsoils arc so leached that the original forest must, for a long period, have derived its mineral nourishment almost entirely from the decay of its own leaf litter. These soils are locally known as the " ironstone " soils because of the characteristic layer of ironstone nodules in the subsoil. In type 37 the iron nodules are generally small and they rarely form a definite band, whereas in type 38 the nodule layer is marked and in places it thickens and extends to the surface. The nodule horizon appears to have been formed not from iron leached from upper horizons, but to have grown in situ owing to extreme fluctuations of soil moisture. The " ironstone " soils are definitely problem soils, and although both grazing and dairying is practised on selected areas much is still unfarmed. The only hill-soil complexes which can be shown on a map of this scale are the semi-mature types 39 and 40. Much of type 39 is bouldery and where farmed is used for grazing. Type 40 is only tentatively placed in this group, and is probably more nearly related to the brown granular clays described below. The soils on the flattish ridge-tops are greyish-brown and the soil granules are coarser than those of a typical brown loam; on the slopes the soils are more fertile and a brighter brown in colour. The original forest cover contained much kauri. The area is used for grazing and dairy-farming. E. The Brown Granular Clays. The brown granular clays are soils formed from rocks which are largely intermediate in composition between the basalts that give rise to the brown loams, and the rhyolites and dacites which give rise to normal podsolic soils. They are high in alumina and iron and consequently are closely related to the brown loams, but the soil clay is generally more sticky and the soil crumbs coarser, especially on the more leached types. Under special conditions of heavy leaching the most mature phase of these soils is the peculiar podsol described under type 17. The immature and semi-mature soils cover easy country (types 41 and 42). They occupy only small areas. The lowland submature type (43) is a brown to greenish-brown infertile granular clay developed under a rainfall of 70 in. to 80 in. per annum. It is used in part for grazing, but pastures are poor and need heavy dressings of lime and phosphate. The upland submature type (44) is a purplish to greenish-brown mottled granular clay occupying the flattish to easy rolling summit of Tutamoe Plateau (2,000 ft. to 2,500 ft. above sea-level), which receives ah annual rainfall of over 100 in. per annum. The underlying rock is in many places close to the surface and the soil is saturated for a great part of the year. Much of the area is still covered with the original forest, but in places pastures have been established. Most of them are poor, and contain much moss, flatweed, and rush. Hill complexes covered by soils of this group occupy a large area. Type 45, a complex of skeletal and immature soils, covers the steep hills. When first converted into pasture these soils are fertile, but the soils on the steeper slopes are, however, shallow and erode easily. The rainfall is heavier over the areas covered by type 46, slips are more common, and the steep hills are more difficult to farm. Much of the forest covering of types 45 and 46 has been cleared, but it is doubtful if the pasture can be permanently retained. Types 47 and 48 cover the rolling to steep slopes ; they are naturally fertile soils, and where cleared make good grazing-land. The soils of type 48 appear to be more leached than those of type 47, but the distinction is tentative. The soils of type 49 are lighter brown and more leached than the preceding types. Some areas are grazed, but pastures are for the most part thin and poor and there is much reversion to second growth. Types 50 to 52 arc complexes of brown granular clays derived from igneous rocks and podsolized soils derived from sediments. They are fairly fertile soils used for grazing and dairy-farming. P. The Ground-Water Soils. All the meadow clays derived from alluvium are included in type 53, although the soils near Ruawai and Dargaville are more fertile than those near Waipu and Hikurangi. The topsoils are grey and the subsoils whitish and mottled. Dairy-farming is carried out on these soils, despite the fact that natural drainage is poor and the soil tends to poach badly in winter. The areas lying within the Hikurangi Swamp are subject to frequent flooding and are consequently but poorly farmed. Adequate drainage is the prime need on this type of land. The meadow granular clays arc derived mainly from basaltic alluvium, and both topsoil and subsoil have a strong granular structure. When drained these soils will support good pastures if adequately manured. Type 55, the peats, have little agricultural value except in some marginal areas where alluvium is intermixed. Drainage of the peat is of little use unless accompanied by consolidation. Type 56 is a complex of sand ridges and peat-filled hollows. The areas on the west bank of the Wairoa River are mainly sandy peats which in many places contain much timber. The soils near Ruakaka are more complex. Close to the sea, ridges of young sand podsol alternate with hollows of peaty sandy loam; farther inland the sand ridges are older and the soils more leached. This area has recently been developed for dairying.

52