STUDIES ON THE LIGHTER SOILS OF THE NORTH ISLAND.

New Zealand Journal of Agriculture, Volume XV, Issue 4, 20 October 1917, Page 196

STUDIES ON THE LIGHTER SOILS OF THE NORTH ISLAND.

I. COARSE PUMICE SOILS.

B. C. ASTON,

F.1.C., Chemist to the Department.

The soils referred to in these studies are the pumice lands of the Central Volcanic Plateau and the dune lands of the coast'. These are both soils of very recent and largely aerial origin (aeolian). The pumice soils have been ejected from volcanoes and rest loosely on the subsoil; the littoral sands have been thrown up by the sea and blown into position by the wind. Where either of these soils is laid down by water, or becomes so situated that water may collect and remain on the surface, swamp conditions appear, which give rise to a large admixture of decaying vegetable matter, and, on draining, a fertile soil results. Where the drainage is better and factors favourable to a stationary condition of the sand-particles are present, forest or scrub eventually appears, and a large amount of humus becomes mixed with the. sand. This when cleared of forest or scrub gives a soil which will grow pasture.

It is in the amelioration and successful utilization of these lands that it is hoped the following pages may prove suggestive. Owing to their large extent a very small improvement in the productiveness of these classes of country must mean a very great increase in produce, and it is the great desire to increase production to the maximum possible at the present troublous time.

POT EXPERIMENTS WITH COARSE PUMICE SOIL.

The following is a record of pot experiments carried out with red clover on pumice soil from the Mamaku Plateau (Rotorua County), situated 1,800 ft. above sea-level.*

The soil used was forwarded from the Mamaku Experimental Farm in clean sacks supplied from the Laboratory.

The seed was red clover from Blenheim, supplied by the Biologist, and germinated before planting on 15th September, 1916.

Fertilizers : The water-soluble fertilizers were shaken with water and sprinkled on the soil. The insoluble substances were applied in finely powdered form. The stable manure was shredded as finely as possible. All fertilizers were thoroughly incorporated with the soil before filling into the pots.

The Jots were kerosene-tins cut lengthwise, and treated inside with paraffin-wax. Holes for drainage were provided, and the soil was filled in over a layer of clean broken bricks. Twenty pounds of damp soil was used in each pot, all pots after filling being of a uniform weight of- 25 lb.

Watering.— The pots were watered at intervals, the original weight of 25 lb. being maintained.

Early Growth.' The pots were examined comparatively on 20th October, when the order of growth appeared to be as follows : Nos. 12, 6 13, 10 • 11 9—T 5, B—7, 3 —-1, 2. At 20th November the order of growth remained apparently the same. The basic - slag pot seemed of a darker green than the other phosphate pots. The leaves of the iron-oxide and ferrous-sulphate pots were also somewhat darker, but those of the spent-oxide pot were rather off colour. ,

• Cuttings. The clovers were cut and weighed at intervals, the following being the results, arranged in order of the dry weight (see manurial scheme for pot-dressings) .: —

NOTES ON THE RESULTS.

The position of the plants in their order of growth on 20th October is instructive. There are evidently some substances which stimulate young growth greatly (such as soluble and insoluble phosphates), some which do not affect the growth at this early stage, and some (carbonate of lime and spent oxide) which are then positively injurious on this soil. This is more clearly seen in the figures for the dry weight of the crop at the first cutting,- about ten weeks after sowing, , when the phosphated and dunged pots are about twice the weight of the control pots, whereas those on the limed pots are less than half of the control, showing deleterious action. It will be noted that the pots are arranged in the diminishing order of the dry weights, and that the green weights sometimes do not fall in the same order.

The effect of phosphates on the whole series is eminently satisfactory in every form in which used, whether the acid (superphosphate) or alkaline (basic slag) mixtures of these, or as the natural rock phosphate. The crescendo effect of. the basic-slag pot up to the fourth cut is remarkable, and is borne out by field experiments.* The excellent average result of the slag-super mixture is - fully shown by the present experiments, and confirms the opinions already expressed in the own'll as to the value of this mixture.'

The effect of the limestone (carbonate of lime, CaCO 3 ) dressings is most instructive compared with the control (unmanured) pots. For the first six weeks there is a deleterious effect produced, which is accentuated with increased dressings. In the next two months the best of the limed pots had caught up and not only passed the control, but had given a better crop than any fertilizer except some of the phosphates and stable manure. Finally, in the last three months of the experiment the limed pots were the best of any.

Of the iron-treated pots the iron oxide (red) has had so little effect that it may be taken as a control pot. The ferrous-sulphate pot (copperas, FeSO 4 in the latter stages of growth has shown > a slight deterioration, while the spent oxide (gasworks refuse), after showing a markedly deleterious action for. the - first three cuttings, improves in 1 the fourth and fifth. Iron . dressings are therefore unsatisfactory though the spent oxide might be further experimented with. Any final beneficial result may be attributed possibly to the large amount of sulphur which this dressing naturally contains.

These experiments were not primarily designed for the purpose of comparing the .relative yields given by soil differently manured, but to ascertain the effect of certain substances on the chemical composition of the clovers. This work is not completed, but the

record of the crop-yield is sufficiently complete and interesting to

publish at the present stage of the investigation, and certain tentative

conclusions may be drawn which should be checked by field experi-

merits before 1 being adopted. It must be remembered that the conditions were artificial, and towards ,the close of the season the plants in some pots would no doubt be suffering from those conditions,

whereas in the earlier stages of growth the conditions were doubtless more favourable than they would have been in the field. If, therefore, it is tentatively assumed that the amount of dry matter produced (i.e., the clover less all water which may be expelled by heating in a water-oven at a temperature not greater than that of boiling water) represents the relative . value of the crop, the following somewhat important deductions may be arrived at and should form the basis of experimentation with similar soil in field experiments.

SUMMARY

On coarse pumice soils phosphates in any form may be expected to produce an excellent result on pasture, owing to the stimulation of the clovers and the stimulation of root-development generally of both grasses and clovers. Limestone exerts a deleterious effect for the first few months, but afterwards a highly beneficial effect. This suggests that lime carbonate gradually becomes changed in the soil into a state more favourable for plant-growth, and that a practicable method of applying lime without loss would not be as a top-dressing for grass, but by its application to ploughed land some months before the seed is sown.

The result with iron dressings is disappointing but not unexpected. Soluble iron salts are well known to be plant-poisons, and insoluble compounds of iron are so insoluble as not to affect the quantity of the yield, though possibly the quality may be improved.

Improvement of the quality of pasture on the type of soil experimented with may be best met by phosphate dressings. Increasing the store of humus by means, of dung or by ploughing-in green manure where practicable, or by increasing the clovers, is to be recommended as a sound proceeding. The effect of liming requires to be ascertained in field trials, and the best method of proceeding determined. It is suggested that a solution •of the 1 difficulty of applying lime to pumice soils may greatly mitigate the necessity for, and therefore the expenditure on,, so much phosphates.

of Storage and Shipping-space.— ln accordance with an arrangement made with the Imperial authorities, the meat-freezing works will this season cut and pack for space-saving purposes all freshly killed mutton and lamb carcases intended for export, subject to labour conditions enabling the work to be carried out. . The method finally adopted differs slightly from that described in the July issue of the Journal, the carcase being severed about 2 in. below the pin-bone, thus leaving ,two chops on the hind quarters. In consideration of ' the extra labour involved by the cutting and packing, the freezing companies will be paid per pound on all carcases so treated.

* Articles on pumice soils which may be consulted with advantage will be found in the Journal for May, 1912 (p. 374), and June, 1913 (p. 622).

* Calculated for 12 plants (11 plants in pot)

* Nos. 4 and 7 (controls) were weighed together and averaged as regards dry weight

* See Journal for November, 1913, p. 525.

Pot No. Dressing. .. . Weight per Pot I Finely ground lime carbonate . . . . >. Grams. 246-00 2 82-00 3 16-40 4 Control (no manure) 16-40 4 Control (no manure) 5 Spent iron oxide from gasworks 8-20 6 Superphosphate (19-5 per cent. PO S 4-10 7 Control (no manure) . . . . . . 8 ■ Ferrous sulphate (pure) .. . . .... - 1-23 9 Iron oxide (red hydrated as used at gasworks) . . 8-20 IO Basic slag (17-8 per cent. P 2 O 5 ) ... 4-10 . ii Makatea phosphate (37-4 per cent. PO 5 ) . . . . 4-10 12 Basic slag and superphosphate (equal parts) . . 4-10 13 Rotted stable manure . . - .. .. .. 164-00

The manurial scheme was as follows: —

Green Dry Green Pry Pot No. Green Weight. Weight. Pot Nd. Weight. ■ Weight Grams. Dry Weight. Grams. Pot No. Green Weight. Grams. Dry Weight Grams 12 . . 70-8 9‘I 9 • • . • • : 32’8 ' 4'5 IO . . • • 73’3 8-9 4 • • .. 29-2 4-2 13 • • 69-8 8-7 . 3 •• . . 12-7 i;9 6 . . 71-6 8-6 5 • • • • ii-5 i.’7 II . . •• 67-7 8-2 2 . . ■ .. 6-i . 1-0 ■ 8 . . ■ • • 35-2 5-o , . . 1 . . 5-2 o-8 7 • • •• 34'3 4’5

FIRST CUTTING, 2ND DECEMBER, 1916.

Green Dry Green Dry Pot No. '.. Green Weight. Weight. Pot No. Weight. Weight ■ Grams Dry Weight. Grams. ■ Pot No. Green ■ Weight. Grams. Dry Weight. Grams. '' 6 . . • ■.. 78-8 ic- 1 7 •• • • 39'9 " 5'5 12 . . • • 77‘ 8 ' 9'7 J 4 •• • • 37’7 ■■ 5'2I .3 • . • • 79'4 9-4 3 •• . •• 25-7 ■ 3-6 II.. • • 70’7 ■ .8-5 ’ 5 •• . . 19-2 2-6 IO . . . • 67-6 8-3 2 . . 109 i-6 9 • • • • 45’ 8 6-o 1 . . •• .8-5 •• 8-5 I;I i-i 8 . . •• 41’7 . 4. 6-o

SECOND CUTTING, 22ND DECEMBER, 1916.

Green Dry Green Dry' Pot No. . Weight. Weight. Pot No. Weight. Weight Grams. WeightGrams. Pot No. . Weight. Grams. Weight Grams. II . . . . 66-2 8’5 3 • • 5. 44-7 6-7 12 . . .. 68-1 8-4. 4 • ■ ; ... 41-2 6*2 IO . . • . . 60-7 8'2 8 ... ' 40-8 ■ 5-8-6 . . . • 60-3 • ' 7-6 2 . . 27-0 4 -i 13 • • • • 59-6 7-1 5 •• 21*1 3’0 7 • • • • 45’3 7-0 1 . . . . 20’9 3’0 9 • • • • 44'9 6-7

THIRD CUTTING, 16TH JANUARY, 1917.

Green Dry Green Dry Pot No. Weight. Weight. Pot No. Weight. Weight Grams. Grams. Grams. , Grams. IO . . • • 96-5 ■ 15-9 3 •• •• 51-9 ii-4 2 . . • • 85-3 14-8 7 • • •• 40’5 8-7 II . . • • 93’2 14-7. 5 •• • • 47'4 7-8 13.. •• 94' 1 • 14-7 9 • • . • • 38-6 7-8 *12 . . . . 94-8 . 14-6 4 • • ' • • 32'6 7-i . 6 . . • • 93'i 13-4 8 . . . • • 32-9 6-6 . 1 . . 72-8 12’5 2.

FOURTH CUTTING, I7TH MARCH, 1917.

Green Dry Green -- Dry Pot No. , ' Weight.. Weight. Pot No. Weight. Weight G: ams. Grams. Grams. Grams. I . . .• . 58-0 12-8 5 • • •• 17-7 4’3 2 . . • • 56-4 II-7 3 • ■ • • 19’7 3’9 13 • • • • 53’7 1 n-6 . 4 . • 9-4 2’7* IO . . • • 55’6 io-6 7 • • •• ■ 15’4 2’7* 12 . . • • 49-1 . 9’4 8 .. . 8-6 2-5 6 . . .. 48-4 9’1 9 • • 10-6 i-9 11.. •• 54’1 . 9-o

FIFTH CUTTING, 22ND JUNE, 1917.