THE EFFECT OF POTASH.

Hawke's Bay Tribune, Volume XIX, Issue 220, 4 September 1929, Page 8

THE EFFECT OF POTASH.

Potash is used largely by all plants in producing the carbohydrates such as starch and sugar. Further it has a very vital effect on the ability of the plant to absorb nourishment from the sunlight and air, though how this process is affected by potash is not yet scientifically clear, certain it is, however, that where potash is entirely absent in the soil the life of the plant comes to an abrupt end.

Where potash, though not totally absent, is deficient, the crops and pasture grass are poor, dull green in colour, with a tendency to wither at the tops of the leaves as though they had been frosted. Clovers and other legumes require considerable potash and it is probable that the improvement in the growth and prominence of these plants following liming is in part due to the fact that lime liberates, a certain amount of potash which previously was insoluble in the soil, COMMERCIAL FORMS OF POTASH. Most farmers and gardeners are acquainted with carbonate of potash, the form in which potash occurs in wood ashes, but from a farmer’s point of view he is interested in oxide of potassium, in which form he purchases it in the commercial potash manures. VAST STORES OF POTASH. According to King, a reliable authority, average sandy soils contain from 2 tons per acre up, while clay soils contain 8 tons or more of potash per acre. Although apparently abundant, unfortunately this is largely in insoluble forms, but in so far as New Zealand is concerned our soil as yet contains sufficient potash for most crops. The only crops which njight require extra supplies being potatoes, mangels, turnips, beet and similar root crops which produce a large amount of sugar and starch Kamit, a product of the Strassfurt deposits in Germany is a form in which potash, when necessary, can be applied in New Zealand. As a result of forest and other growth during thousands of years past, and also in animal form, potash is fairly absorbant in most of our soils, but much of this supply, as previously stated is unavoidable, unless it is acted upon by the various “amendments” previously referred to as potash manures are expensive, this method of increasing the available supply—i.e. by means of “amendments,” — where necessary is by far the cheapest, and it will therefore be of most practical interest to the farmer if we proceed to discuss these. “AMENDMENTS.” / Lime, in its native form, limestone, is fairly well known to all New Zealand farmers, and it is very often assumed that because outcrops of limestone rock occur on country the soil of that locality must necessarily contain abundant lime. This has been proved to be an entirely erroneous conclusion because carbonate of lime is so readily dissolved by the carbon dioxide contained in limestone subsoil it is quite probable that the lime has been leached there from to a level, below the reach of grass plant roots.

take out the papers and note the shade of colour. If the papers still remain blue the soil is alkaline or neutral and does not require lime, while the various shades varying from pale pink to red will indicate the amount of acid in the soil at various points sampled, and give some indication of the amount of lime required to correct the condition. VARIOUS FORMS OF LIME. Lime can be applied in three forms, i.e. ground limestone, which is slow acting but safe to apply to any type of soil, especially desirable for light, sandy, gravelly, tr pumacious soils lacking in humus, quicklime which is produced by burning limestone and expelling the carbon dioxide gas which it contains: and slaked lime, which is quicklime which, for agricultural purposes, has been slaked by being exposed to moist air, rain, and dew, when it again takes up a considerable amount of the carbon dioxide expelled by burning. Quicklime and slaked lime are caustic, and hence objectionable to handle, but are much quicker in their action than is ground limestone. On heavy clay lands, and on peaty and similar soils containing a large amount of humus, quicklime and slaked lime will have more rapid effect than limestone and will not damage the soil, but rather considerably improve it-.

TESTING FOR LIME REQUIREMENT. A sure test for acidity or lack of lime, which any farmer can make, is with litmus paper, which can be purchased cheaply from most chemists in little booklets. Open the soil sufficiently with the blade of a pocket knife to insert a small strip of litmus paper, then press the soil close about the paper. Repeat this process at various points about the area to be tested, marking each paper with a stick. In an hours time carefully