TREATING LIGHT LAND.

Auckland Star, Volume LX, Issue 227, 25 September 1929, Page 23

TREATING LIGHT LAND.

METHODS WITH PLOUGHABLE COUNTRY. GREEN MANURING AND OTHEB PRACTICES. (By SUNDOWNEE.) In previous articles dealing with "commercial fertilisers," I have briefly covered the composition, effect on growth and nutritive value and suitability foi particular soils and climates, of the chemical fertilisers of chief interest to New Zealand farmers, and have touched also on the principal soil "amendments, 5 ' which, while not in themselves manures, have a chemical action on insoluble matter already present in the soil, converting this to a soluble form. . There is, however, a large area of land in the Dominion which, cither because of its remoteness from rail or port, or because of its natural poverty in humus, it would not pay to top-dross with the ordinary commercial fertilisers or even with the soil amendments. In the North Island a considerable area of this poor land is of volcanic origin and is unusually deficient in humus, is acid and, indeed, lacks phosphates, nitrogen and potash. Because of its extent this pumice soil is of considerable importance to the Dominion, and any method which can be devised of raising the fertility of this land must reflect on the prosperity of the whole country. Top-Dressing Too Costly. Theoretically, the application of ground limestone in considerable quantity to cure the acidity and liberate the plant food already in the soil, followed by liberal top-dressing with blood and bone manure which would supply phosphates and nitrates in an organic and neutral form would be ideal. The high initial cost of these dressings, however, coupled with the cost of cartage and application, makes their use prohibitive on land the original freehold cost of which may range from 2/0 to 10/ per acre. Grassing Following Turnips. Where this land is ploughable it is often possible to bring it into fairly good grass by growing and feeding off a crop of turnips, Avhen the manure from the grazing stock provides sufficient available plant food to establish and maintain some of the second quality grasses for several years, besides which the trampling of the closely-held animals tends to consolidate the surface soil, thus encouraging the flow of subsoil moisture by capillary action upwards to the roots of the plants. Grasses to Follow Turnips. It is a mistake on pumice lands of this sort to sow Italian rye, perennial rve, and on some soils even cocksfoot, following turnips, for these, are all gross-feeding grasses and quickly exhaust the available plant food introduced through the animal manure. A much sounder practice is to sow deeprooted grasses of inferior quality, using the animal manure to establish these firmly, when a moderately good pasture will result, which will stand for many years. It is also of extreme importance that the solidity of the soil should be disturbed as little as possible at the time of sowing the grass, and for this reason it is good practice to broadcast the grass seed mixture before the stock have finished grazing the , turnips, harrow or disc the land with the dual object of lifting the turnips and covering the seed, and allow the stock to tread the seed firmly into the soil. Green Manuring. Where a still more permanent pasture of better quality grasses is desired, it is possible to introduce the plant foods which are chiefly deficient in this pumiceous soil by means of growing and turning under a green crop. This is generally known as green manuring. For the purpose of green manuring it is usual to sow the ploughed land fairly heavily with one or other of the legumes, which include peas, vetches, lupins, etc. These are used in preference to other quick-growing plants, such as oats, rape and so en, because they take very little nourishment from the soil, extracting most of their requirements, apart from moisture, from the air, produce an abundance of succulent and readily-decomposed stem and leaf in a short growth period and have the peculiar ability of extracting nitrogen from the atmosphere and fixing it in themselves and in the soil. At the same time any luxuriant growth, such as fathen, chickweed, rape, barley, oats, etc., which will provide a bulk of green material, may be profitably used. When the green crop has reached its maximum growth, but before it has come to the woody stage, it should be ploughed under and consolidated as much, as possible by rolling. On the firm seed bed thus produced the grass should be sown. The Effect of Green Manure. This green mstnure serves several purposes. In the first place it provides a quantity of humus, which is naturally deficient, in these pumice soils, in which soil bacteria can breed and thrive and do their useful work of converting insoluble mineral and organic matter into available plant food. This body of decaying vegetable matter also retains the soil's moisture near the surface, and hence available ■ to the grass roots. Awain it adds "body" to the surface soil, causing it to compact more firmly,, a condition most desirable for grass growth.' Finally it provides a steady supply of nitrogen and potaeh which is usually sufficient to maintain the better grasses for a number of years. Unploughable Light Lands. While green manuring is better than sowing after turnips, it is also more expensive, for with the latter the grazing of the crop frequently pays for the cost of working plus grass seed. Both, however, can only be conducted on ploughable land, and as there are considerable areas of this light land which is not ploughable, some method must be devised of cheaply introducing the tiumue, nitrogen and potash of which it is m need without having to turn up the soil. No doubt there are handsome profits iwaiting the farmer with such land who jan solve this problem. The greatest hope of success would appear to lie inKTio /lirppfrmn -nf smvincr _+Jift-lsmd ./limm-l

following a burn with all the tap-rooted varieties of the legumes which the farmer could purchase cheaply. Bed clover or cowgrass, white clover, lotus major, trefoil, lupin, etc., should thrive on such soil and by their nitro-gen-gathering propensity and the decay of their roots and foliage in and on such land- they should build it up fairly rapidly to a permanent grass standard. Deep-Rooting Grasses Needed. It must be remembered that in dealing with this light, porous soil, only plants and grasses with deep-rooting or taproot habits can survive, for they are the only ones that can reach down to the depths where the soil is sufficiently consolidated to retain the moisture. Whatever growth of an edible nature for stock the farmer can prevail on to grow on such country is valuable, for it is largely by the trampling of the stock in search of such fodder that the surface soil will be consolidated and enable the better grasses to become established.