GRASS FERTILISERS.

Putaruru Press, Volume VII, Issue 320, 24 December 1929, Page 6

GRASS FERTILISERS.

ESSENTIAL PLANT FOODS. The Part Played by Each. The following is the text of an aadress on the above subject delivered in Hamilton recently by Mr W. Alexander, agricultural adviser to Messrs Kempthorne, Prosser and Co., Ltd # There is no more important question facing the farmer to-day than that of maintaining the fertility of the soil, said Mr Alexander. We are continually being impressed with the fact that the major portion of the wealth of this country is derived from the export of primary products, and it is only fitting that we should guard closely the sources of such wealth. Success in farming any land to-day depends wholly on the correct use of artificial fertilisers, as these are the instruments by which soil fertility is maintained. Science has shown us that the products of the land are made up of certain mineral and organic materials, and that the soil is merely the storehouse where such essential materials are to be found. {Soil that is deficient in any one or more of the essential plant foods cannot be described as truly fertile. As in a chain, so it is in soil that the strength of the whole is just as strong as the weakest link. A shortage in any one of the essential ingredients cannot be made good by applying excess quantities of other eleyments. The application of any artificial fertilise-s snouid always do directed to the production of butter-fat, meat or wool, rather than to the prouuction of grass alone. It is possible to produce grass to-day that is not of right quality either fiom the point of view of the stock or the final product. If it is realised that every pound of butter-fat, every bit of wodl, and every carcase of meat contains its due proportion of several different mineral substances, then it w r il] be understood how necessary it is that complete fertilisers be used.

The Essential Plant Foods There are at least nine or ten different elements required to provide complete sustenance to plants, and through plants to the animals in the fields. Fortunately for us most soils contain sufiicient quantities of a number of these essentials, so that, except in very rare circumstances, we need have no further worry about these. There are still four elements, however, that do require attention, and these in the order of their importance are lime, phosphates, potash and nitrogen. Let it be clearly understood that no two of these ingredients serve the same purpose. it is not possible to make potash do the work of phosphates, nor can one replace potash with nitrogen. Each has itK own particular part to play., and each assists the other ingredients to play their parts successfully #

The Effect of Lime Lime has a two-fold function to perform—namely, chemical and mechanical. On the chemical side lime acts as the liberator of what might be called dormant plant foods, whilst on the mechanical side it improves the texture of a soil and makes it a more suitable habitation for soil bacteria. To a great extent lime is the foundation upon which successful agriculture is based.

' Phosphates Of all the artificial fertilisers used in building up the fertility of the land phosphates are of outstanding importance. Mr B. C. Aston, chemist to the Department of Agriculture, has put on record the following statement: — ‘ ‘Phosphate, it is only right, should bulk greatest in the farmer's manure bill. There does not seem to be any reason to worry about nitrogen or potash supplies, but the increasing demand for phosphate suggests that every precaution should be taken to ensure that the full value is obtained from the use of it. * ’

Mr Aston also adds that after some years spent in analysing soils from all parts of the Dominion for their manurial ingredients, broadly speaking, soils or the northern part of New Zealand, especially those of Auckland, were deficient in phosphates. Phosphate de. ticiency of soil is the -outstanding defect throughout New Zealand, and it is the means of supplying this deficiency that must be first considered.

The Functions of Phosphates Phosphates stimulate root development in pasture plants and crops, and food supplies from a wider and deeper soil area and also to more effectively resist drought conditions. Phosphates also supply the very necessary bone and sinew-building foods. It is a wellestablished fact that the health and productivity powers of all classes of. live stock are dependent upon an ade-1 quate supply of minerals, and of these j minerals phosphates are of outstanding importance. | The work of Theiler and his associ-j ates in South Africa has shown that' lack of phosphorus in the Transvaal j pastures limit the rate of growth in I young stock and the milk yield ofj cows. IDr Woodman shows that a cow yielding 4 gallons of milk per day re-1 quires 3£oz of phosphate in its daily ration—add to that the requirements j of the cow herself, and the calf which she carries every year, and it will bel seen that there is an ever-constant

drain of the phosphate resources of the soil. The amount of phosphate in the soil then becomes an important one, and one that should be studied by every primary producer. Unlike nitrogenous fertilisers, phosphates are not readily lost in the soil. A Theory Disproved

There was a time when farmers held that it was fatal to apply superphosphate at a time other than in the spring, as all the good of the fertiliser would be lost before the growing season commenced. That theory has been completely disproved, both by the farmer and the scientist. The explanation lies in the fact that phosphoric acid never lies free in the soil, but goes into combination with a mineral base, and is only liberated as required by plants. Farmers have a great variety of phosphatic manures to choose from, and the matter of making a decision is not always easy. As a general rule superphosphate stands alone as being at once the most soluble and consequently most effective form of phosphate to use. Thci’e are occasions, however, where super does not give the best results, and it will almost invar iably be found that on such occasions the land treated will be definitely short of lime. The small amount of lime or

gypsum present in the super is not suf ficient to counteract the acidity of the soil nor prevent the phosphoric acid from linking up with an iron or alu rnina base. In such cases the obvious tiling to do is to add lime to the soi, or to use a lime phosphate such as basic super, basic slag, or a mixture of super aud lime phosphate such as Seychelles guano. Potash

Potash plays an important part in animal nutrition, and as yet its real value is scarcely understood by New Zealand fanners. Unlike nitrogenous or phosphatic manures, potash rarely makes any great iifipression upon a pasture, and because of this fact users arc inclined to think that it is cither not required or not suitable for their particular land. In this connection let me point out that no one can tell by mere observation whether or not the required pinch of salt has been added to the porridge cooked for breakfast; yet no one will dispute the importance of adding that little bit of salt. Potash represents to stock just what salt represents to us, and it should not be judged by its ability to raise the yield of grass, but rather by its capacity to improve the quality of grass. Potash will greatly improve the health o’ stock, and on this account alone should not be left out of any top-dressing mixture

Nitrogen This, the last of the 1 ‘Big Four, y * is perhaps the most difficult of all to dea. with, because of its great power to promote good or evil according as it is used. A very necessary ingredient of every soil, but insofar as Waikato soils are concerned it is generally present in adequate quantities. Nitrogen stimulates root growth and is very effective in promoting early growth, but can only be used safely on land that has already been well treated with lime, phosphates and potash. Conflicting opinions exist as to the value of soluble nitrogen as a top-dressing for grassland, just as opinions differ as to whether or not straight rye-grass makes a better pasture or hay crop than docs a mixture of grasses and clovers. Dos pite conflicting opinions, it is admitted by those most concerned that soluble nitrogen should only be used on land that has already been properly treated with minerals, and with this every user will no doubt agree. Pastures have other means of securing nitrogen than by the application of artificials, but they have no means of securing lime, phosphates and potash other than those adopted by the farmer who top-dresses intelligently.