H.—34

CHEMICAL WORK ON THE SOILS OF WESTERN TARANAKI AND NORTH AUCKLAND. (By T. Rigg.) The chemical work necessary for the characterization of soil types identified by the field-workers in Taranaki and in the Waikato has been done partly at the Dominion Laboratory, Wellington, and partly at the Cawthron Institute. Mr. F. T. Seelye, of the Dominion Laboratory, has continued his work in connection with the fusion analyses of samples taken from different soil profiles, and has supplied much valuable information concerning the chemical processes which have operated in soil formation. The work at the Cawthron Institute has been connected mainly with a study of the surface soils. Determinations of textural characteristics, of lime status, of soil acidity, and of plant-food content have been carried out by Miss E. B. Kidson and L. Hodgson on a large range of Taranaki soils, and much information has been gained thereby. Taranaki Soils. Texture of Taranaki Soils. —Mechanical analyses made by Troell's method of soil samples taken to a depth of 6 in. have shown the great uniformity in texture of soils derived from the Egmont ashshower. Samples collected from different points in both south and north Taranaki reveal the great constancy in the percentages of the sand, silt, and clay fractions. Typical analyses of samples taken from Waitara in the north and Manaia in the south are shown in Table I below. In both cases the soils belong to the loam group and contain 10-12 per cent, of clay and 18-20 per cent, of the silt fraction.

Table I.—Typical Mechanical Analyses of Taranaki Soils.

Notes.—Sample 487 from Bell Block, junction of main VVaitara and Inglewood roads; sample 443 from Manaia State Farm, Waimate West; sample 431 from Toko Railway-station; sample 429 from virgin soil, Stratford Demonstration Farm; sample 487 taken 1-7 miles north of junction of Lepperton and Mountain Roads; sample 455 from upper end of Hastings Road. The soils derived from the Stratford ash-shower show much greater variation in textural properties. At Stratford and its immediate vicinity the texture of the soils falls into the coarse sand group. At Inglewood soils belonging to the sandy loam group are more typical. The presence, however, of a considerable amount of fine gravel, both in the surface and sub-strata of Inglewood soils, makes them more open in texture than is indicated by the mechanical analyses. Samples taken from Kaimata and Toko show that, at these centres removed some distance from the centre of volcanic eruption, very coarse particles are generally absent from the surface soils. The soils contain large percentages of the sand fraction, and fall into the medium sand category. Soil samples taken from the very recent ash-shower (the Burrell Shower) were found to belong to the gravelly sand texture. The coarse-sand fraction amounted to over 45 per cent., and, in addition, the soils contained 14-15 per cent, of small stones. Lime Status of Taranaki Soils. —Determinations of lime requirement and of pH value have been made on a number of soil samples taken from the different soil types. The pH values show, with few exceptions, a very small range, figures between 5-85 and 6-08 being usually obtained for the top 0-3 in. spit. As a rule, the pH value for the 3 in.-6 in. spit is a little lower than the top 0-3 in. spit, and in both cases indicate that the soils require only small applications of lime for pasture purposes. The Patua soil, derived from mixed volcanic ash in the high-rainfall belt of Mount Egmont, has a lower pH value (5-71) and shows more need of lime treatment. As might be expected, the peaty soils of Eltham have a marked acid reaction, and beneficial results should be obtained from lime treatment. Considering the large percentage of organic matter associated with Taranaki soils, the lime-require-ment figures are not high. They show that the soils are unsaturated in regard to lime, but do not necessarily indicate high lime-deficiency in the soil. Average lime-requirement figures and pH values for all the more important soil types are shown in Table 11.

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Ash-shower Bgmont. Stratford. Bnrrell. Locality .. .. .. Waitara. Manala. Toko. Stratford. Inglewood. Stratford. Laboratory No. .. .. 487A. 487b. 443a. 443B. 431A. 431b. 429a. 429b. 483a. 483b. 466a. 466B. Depth of sampling O-Sin. 3-61d. 0-3in. 3-6in. 0-3in. 8-6in. 0-3in. 3-6in. 0-31n. 3-6in. 0-8in. 3-6ln. Coarse sand .. .. 17-9 22-4 18-6 22-4 25-3 27-2 41-7 45-4 28-8 32-3 47-4 43-6 Finesand.. .. .. 16-5 17-6 21-9 22-2 19-7 21-8 14-1 17-6 16-4 16-4 13-1 19-1 Very fine sand .. .. 8-9 6-7 8-3 9-5 7-4 7-9 6-0 7-8 5-1 6-3 8-2 7-2 Silt .. .. .. 18-8 19-5 22-0 21-8 17-5 18-9 10-2 10-4 14-5 13-9 11-4 12-6 Clay .. .. 12-4 11-2 10-5 8-5 3-3 3-2 2-4 1-1 9-6 8-3 4-2 3-0 Loss on ignition .. 30-2 24-0 22-7 17-2 23-4 19-1 23-2 14-3 26-8 21-2 17-9 11-9 Difference.. .. —4-7 —1-4 —4-0 —1-4 3-4 1-9 2-4 3-4 —1-2 1-6 —2-2 2-6 Stones .. .. .. 2-5 3-3 Nil Nil 5-2 11-2 Nil 8-8 10-9 16-1 15-4 14-1 Fine gravel contained in coarse Nil 2-9 3-4 5-9 1-5 2-6 3-1 4-9 8-6 10-2 15-9 10-0 Soil type .. .. .. Loam. Loam. Medium Coarse sand. Coarse Gravelly sand. sandy loam. sand.