SOME SOILS OF OTAGO PENINSULA.

New Zealand Journal of Agriculture, Volume XXVII, Issue 4, 20 October 1923, Page 219

SOME SOILS OF OTAGO PENINSULA.

F.I.C., F.N.Z.Inst., Chemist to the Department.

B. C. ASTON,

Otago Peninsula is one of those remarkable areas of volcanic origin in the South Island which occur as prominent features of the coastline physiography, but which rarely occur far from the coast, and then only in unimportant masses. Banks Peninsula and Otago Peninsula, with their related contiguous areas, are the -two great instances of this type of country that the South Island affords, which are highly important from an agricultural viewpoint, and therefore deserving of intensive study. As an instalment towards this consummation the following notes are offered.

Otago Peninsula was originally an island, isolated as a result of a submergence which drowned two valleys and the divide between their heads, forming a strait. The peninsula is now joined to the mainland by a sandy isthmus which originated as a bar across the southern entrance to the strait (Cotton, 1922). Over this isthmus runs the Anderson's Bay Road —the land means of access to the peninsula. In the early days of the Otago Settlement the country was forested, but now only isolated patches of “ bush ” remain, and the whole occupied area is practically devoted to dairy-farming. The peninsula presents some notable geological features. On the ocean or south-east side the sand has blown up from Sandfly Bay over a mountain more than 1,000 ft. high, so that as far as altitude is concerned Sandymount may be considered one of the most remarkable sandhills of the Dominion. Near here is also a blowhole and some basaltic pillars which are among the finest to be seen in New Zealand.

In February, 1920, the writer was able to. pay a visit to this district and to collect a few samples from the waste and other virgin lands which appeared likely to afford interesting information. The dune-sands of the coast were collected from two widely separated localities, and proved rich in mineral plant-foods, similarly to some sands of the North Island described in the Journal for May, 1920, page 274. Littoral soils of a volcanic origin, subject to the action of sea-spray or of sea-inundation, were also collected, and show a very high potash content, while phosphate was present in good proportion. In a virgin forest soil at good elevation and derived from a volcanic rock all plant-food was found to be present in good degree. This soil was classified as a silt loam, and would be much heavier to work if it were not for the excellent effect of the high amount of organic matter present.

Only two samples were collected which did not represent virgin soils. One on Tomahawk Head, down in good pasture, appears to have been depleted in phosphate, other plant-foods being present in good proportion. The other was from a grassed paddock on the slopes of Harbour Cone. This soil was extremely rich in available phosphate and potash, and exhibited a well-nigh perfect mechanical composition

or texture. This Harbour Cone soil is not singular among ■ peninsula soils in its high phosphate content. A soil from North-east Harbour which contained 0-04 per cent, of available phosphoric acid yielded in 1908 41I tons of turnips per acre without any manure.*

Sandy soils derived from the dune-sands of the coast occupy a comparatively large area of the low-level soils of the peninsula, and if the results obtained can be taken as true for the whole of these soils it is time that some scheme of improvement were set on foot ultimately to enable them to be grassed.

Further investigation of the soils of the Dunedin area will, be proceeded with as time and opportunity afford, with a view to the completion of a soil survey. -

NOTES ON THE SAMPLES ANALYSED (SEE TABLES).

L 856 was taken at the top of the cliff, 200 ft. above the Tomahawk Beach, in a discontinuous salt-plant association, consisting of patches of Chenopodium glaucum, Sonchus, and Senecio lautus. This association occupies a strip some yards wide from the edge of the cliff, and the sample was taken in this area, the following sample (L 858) being taken in the adjoining area, which was grassed with rye-grass. The difference between the ease with which the salty area and the difficulty with which the grassed area was sampled was great. The sampler was only with much difficulty inserted into the latter soil. These fine sandy loams are remarkable for the high amount of available and total potash they contain. It will be seen that,in. the subsoils of these samples the lime-magnesia ratio is abnormal, there being more magnesia than lime extracted by the citric-acid method, while in the surface soils the proportion of each element is about the same. It is probable that such magnesia owes its origin to the sea-water blown inland as spray. The writer considers that the proportion of citric-acid-soluble magnesia present in arable soils should not exceed that of the lime. It will be noted that the available phosphate is present in larger amounts in the soil (L 856) near the cliff than in the soil (L 858) farther away. These soils are derived from a volcanic rock, trachyte, which underlies them, according to Dr. Marshall (1906). Trachyte contains a large amount of silica, potash, and soda, whereas basalt contains much less silica and more lime, iron, and magnesia.

L 860/1 and L 864/5 are coarse sandy soils, the dune-sands of the coast wind-carried to their present situation some distance from the seashore. The first soil and its subsoil (860/1) differ from the next (864/5) n that there are a comparatively recent dune-sand near sea-level, whereas the latter is from more ancient dune near the top of Sandymount, about 1,000 ft. elevation. The recent dune is very high in available phosphate, and is also high in potash. The ancient - dune, while still fairly high in phosphate, has a subsoil which is decidedly deficient in total phosphate. The richness of the wind-blown sands of this district in mineral plant-food shows that the soils only require

fixing and reclaiming in such a way with a plant covering that, when sufficient organic matter has been introduced, suitable grasses may be planted, and thus finally a permanent sward be established. An active foresting policy might prove the first stage to the economic reclamation of the most intractable of the sands. All the elements except nitrogen are present . in good proportions for the growth of ordinary farm-crops suitable for light sandy country. Nitrogenized organic matter could be accumulated in the soil by foresting the area or by growing suitable plants, such as lupins, &c. One would think that pine plantations would be a great asset to this thickly settled district for the timber produced as well as for the beneficial effect on the soil.

L 862/3, 866/7, an d 868/9 represent the type of soil which is the mainstay of the farmer in all countries-the loams.

L 862/3 were collected on the upper road of the peninsula, at an altitude of 500 ft., in the remains of forest consisting of rimu, totara, mahoe, fuchsia, broadleaf, bramble (Rubus australis), elderberry, coprosma (several species), Panax Colensoi, Drimys, and Muehlenbeckia australis.

L 866/7 were collected on the slopes of Harbour Cone in rye-grass, clover, and timothy pasture. This soil has an abnormally high phosphate content. Silt is the largest fraction, therefore the soil should possess a sufficient but not. too great power of retaining water. The fine silt is lower than the clay, which is present in satisfactory amount. As there is a. considerable amount of fine sand, the absence of coarse sand is no disadvantage. One would ' predict high fertility for this soil from a consideration of its physical and chemical characters and climate, and a profitable return to its owner owing to the proximity of the locality to the market.

L 868/9 were taken in a salt-marsh plant association at the foot of Harbour Cone, on the shores of Hooper's Inlet. The soil is a silt loam resting on a fine sandy loam, and is subject to inundation by the brackish water of the inlet. The abnormally high potash content and the unbalanced lime-magnesia ratio are characteristic of salty soils, as is also the good amount of phosphate present. ' The proportion of silt is rather too high, but this might be remedied by bringing up some of the sandier subsoil when these siltv soils come to be reclaimed.

Nosema apis, the prdtozoon occupying the epithelial cells of the chyle stomach of bees, has been traced to many parts of the Dominion, and it would appear to be almost universal. Its presence in bees, however, cannot be associated with any acute disorder in New Zealand, though minor troubles have been occasionally found present in bees harbouring the organism.

Phosphates in New Zealand. — new locality for the occurrence of phosphate rock in New Zealand apparently exists in the North Auckland district. Mr. H. Parsons, of Rawene, Hokianga, forwarded to the.Department’s Chemical Laboratory last year a specimen of rock which contained 11-12 per cent, phosphoric acid, equal to 24-4 per cent, tricalcic phosphate. A specimen of greensand, received from Mr. L. W. Kempthorne, of St. Andrew’s, near Timaru, was found to contain 40 per cent, phosphoric acid, equal to 8-95 per cent, tricalcic phosphate.

* See K 2709, fine sandy loam, in the annual report of the Dominion Laboratory, 1909 (page 54). K 2708, loam, and L 50 and 51, fine sandy loams (referred to in the same report), are also from the same locality, but do not exhibit the same excellence in chemical composition.

Laboratory No. Locality. Matter. Total Nitrogen. i-per-cent. Citric-acid Extract, Dyer’s Method ; Hall’s Modification (“Available” Plant-food). Hydrochloric-acid Extract (“Total ” Plant-food). I Total Nitrogen. r-per-cent. Citric-acid Extract, Dyer’s Method ; Hall’s Modification (“Available” Plant-food). Hydrochloric-acid Extract (“Total ” Plant-food). At C. On Ignition. Lime, CaO. Magnesia, Mgo. Potash, k Phosphoric Acid, Lime, CaO. Magnesia, MgO. Potash, o. Phosphoric Acid, 856 Tomahawk Head 4’44 10-13 0-238 o-iio 0-104 0-064 0-022 o-94 I-II o-55 0-18 857 Subsoil of 856 .. 4-68 7-30 0-150 0-083 0-109 0-045 0-008 o-88 1-08 _ o-57 0-12 858 Tomahawk Head 2-98 8-04 0-202 0-082 0-079 0-043 0-008 0-89 0-64 o-6o 0-07 L Subsoil of 858 .. 2-70 5-5i 0-095 0-052 0-066 0-038 0-005 o-86 0-70 o-59 0-03 L Tomahawk Beach 0-18 1-06 0-025 0-115 0-022 0-033 0-061 o-8i 0-24 0-13 0-14 861 Subsoil of 860 .. O-I2 0-64 0-014 0-092 0-020 0-037 0-058 > 0-70 . 0-21 0-12 0-09 L 862 In virgin forest 7-70 - 25-01 0-516 0-157 0-102 0-039 0-024 0-50 0-65 0-29 O-II 863 Subsoil of 862 .... .. 6-90 12-69 0-210 0-056 0-057 0-036 O-OII 0-29 0-72 0-25 o-io . 864 Sandymount .. .. ... 0-48 1-91 0-050 0-062 0-025 0-026 0-022 o-44 0-21 0-09 0-08 865 Subsoil of 864 .. 0-48 x-55 0-039 0-068 0-033. 0-021 0-026 0-46 0-22 0-08 0-03 L Harbour Cone .. 3-92 12-59 0-338 o-i74 0-077 0-070 0-063 0-84 0-50 o-68 0-15 867 Subsoil of 866 .. 2-86 9'63 0-167 0-080 0-05 r 0-055 0-019 0-72 0-52 0-70 0-06 L Harbour Cone (foot) .. 6-48 18-03 0-614 _ 0-151 0 •200 o-i73 0-020 o-74 o-6i 0-57 o-r8 L 869 HeadTomahawk of . 3'20 8-14 0-209 o-n8 0-140 O-I93 0-021 0-92 0-62 o-45 O-II ■ V MECHANICAL ANALYSES. (Results are percentages on air-dried soil.) Analysis of “ Fine Earth ” passing mm. Sieve. 1 Stones • and Lab. (Classification of United No. States Department of Agriculture modified.) Fine Gravel. Coarse Sand. FineSand. Silt. Fine Silt. Clay. and Loss on Gravel Ignition. L856 Fine sandy loam 0-2 8-6 2 I-I 28-7 13-6 14-9 13'8 Nil. L 857 Nil 9’4 21-4 28-4 io-i 20-7 n-6 ** L858 •.. 9-8 22’4 31-4 ro-3 i7-4 ro-8 L 859 5-6 24-9 29-1 IO-I 23-3 8I L 860 Coarse sand .. 82-8 14-5 0-5 0-4 Nil 1-3 «« L 861, Silt loam 80-9 16-9 o-4 o-3 «« o8 Trace L 862 2-7 9’4 23’3 13-7 21-7 . 30-7 Nil. L863 3’9 n-9 24’3 15-8 28-1 18-7 L864 Coarse sand .. 84-3 1 r-4 I-I o-3 Nil 2-4 Trace L865 85’5 10-5 I-I o-5 16-7 20 Nil. L 866 Fine sandy loam i-5 18-3 37-6 n-3 16-0 Trace ' L 867 " . P-5 24’3 31-6 12-4 18-2 12I Nil. L 868 Silt loam 2-6 9-3 38-1 13'3 II-2 23’3 Trace. L 869 Fine sandy loam 5’5 3 r-6 33'2 8-2 10-4 III Nil. Subsoil of 856 . . Tomahawk Head Subsoil of 858 .. Tomahawk Beach Subsoil of 860 .. In virgin forest Subsoil of 862 .. Sandymount Subsoil of 864 .. Harbour Cone .. Subsoil of 866 .. Harbour Cone (foot) ... Subsoil of 868 .. 4'44 4-68 2-98 2-70 o-x8 0-12 7-7o 6-90 0-48 0-48 3’92 2-86 6-48 3'20 10-13 7'3° 8-04 5-5i x-o6 0-64 25'01 12-69 1-91 1'55 12-59 9'63 18-03 8-14 0-238 0-150 0-202 0-095 0-025 0-014 0-516 0-2X0 0-050 0-039 0-338 0-167 0-614 0-209 O-IIO 0-083 0-082 0-052 0-115 0-092 o-i57 0-056 0-062 0-068 o-i74 0-080 0-151 0-118 0-104 0-109 0-079 0-066 0-022 0-020 0-102 0-057 0-025 0-033. 0-077 0-051 0-200 0-140 0-064 0-045 0-043 0-038 0-033 0-037 0-039 0-036 0-026 0-021 0-070 0-055 o-i73 O-I93 0-022 0-008 0-008 0-005 0-061 0-058 0-024 O-OII 0-022 0-026 0-063 0-019 0-020 0-021 0'94 o-88 0-89 o-86 o-8x 0-70 0-50 0-29 o-44 0-46 0-84 0-72 o-74 0-92 i-ix 1-08 0-64 0-70 0-24 0-21 0-65 0’72 0-21 0-22 0-50 0-52 o-6x 0-62 o-55 o-57 o-6o o-59 0-13 0-12 0-29 0-25 0-09 0-08 o-68 0-70 o-57 0-45 0-18 0-12 0-07 0-03 0-14 0-09 O-II o-io 0-08 0-03 0-15 0-06 0-18 O-II MECHANICAL ANALYSES. (Results are percentages on air-dried soil.) Descrintion of Soil. Analysis of “ Fine Earth ” passing mm. Sieve. V Stones and Gravel Lab. No. (Classification of United States Department of Agriculture modified.) Fine Gravel. Coarse Sand. Fine Sand. Silt. Fine Silt. Clay. Moisture and Loss on Ignition. L856 L 857 L858 L 859 L 860 L 861, L 862 L863 L 864 L 865 L 866 L 867 L 868 L 869 Fine sandy loam Coarse sand .. Silt loam Coarse sand .. Fine sandy loam Silt loam Fine sandy loam 0-2 Nil 89'4 95'6 82-8 80-9 2-7 3'9 84'3 85'5 i-5 o-5 2’6 5’5 2I-I 2224'9 14'5 ’ 16-9 9'4 n-9 n-4 io-5 18-3 24'3 9'3 31'6 28-7 2831'4 29-o-5 0'4 23'3 24'3 X-X i-i 3731'6 3833'2 13'6 io-i 10-3 IO-I 0-4 o-3 13'7 15'8 o-3 o-5 ii'3 13-8-2 14'9 20-7 1723'3 Nil 21'7 28-1 Nil 16-7 18-XI-2 10-4 13-8 ix-6 10-8-r i'3 0-8 30-7 18-7 2'4 2-0 16-0 I2-I 23-3 11Nil. Trace. Nil. Trace. Nil. Trace. Nil. Trace. Nil.

SOILS OF OTAGO PENINSULA.-CHEMICAL ANALYSES. (Results, except *, are percentages on soil dried at 100º C.)