SOIL FERTILITY AND PLANT LIFE.

Shannon News, 1 November 1927, Page 3

SOIL FERTILITY AND PLANT LIFE.

' HOW OUR PRIMARY PRODUCTS ARE BUILT UP. (Prom the Levin Chronicle). Useful information as to soil improvement was given by Mr F. E. Parker, in an address entitled, "Plants and Plant Foods," at the monthly gathering of the Levin Chamber of Commerce ' Lunch Club at the Oxford rooms on Friday.' There was a good attendance presided over by Mr. E. S. Crisp, who introduced the speaker. Whether from the aspect of the.farm, the garden or the cabbage patch, said Mr.'Parker, all were interested in some wav in the productivity of the soil. The resources of the soil comprised the permanent capital on which the welfare of the community depended, and in the case of New Zealand almost the whole of the export was of primary products. Yeai-3 of scientific research had dhown that .many substances were required to sustain'plant life. Of the elements which served as plant food, about 90 per cent., came from the atmosphere, and the balance from soil fertility. On first thoughts one would say that the element of importance was the atmosphere, because it contained the great bulk of plant requirements: but this was noi so, as soil fertility was the all-important and governing factor. There were many elements that made up plant food, but they could be pretty well reduced to a few essentials. The atmospheric resources were oxygen' ( nitrogen, carbon'and hydrogen. The | soil contained four essential ingredients ; —phosphoric acid, lime, potash, and , nitrogen. With regard to lime, ex- j pert's differed somewhat on the questipn' j whether it was a food or an agent; | but it was sufficient to say that it was j an essential in the ground as a plant. | food. Carbon constituted the. 'main i

source of the dry matter in any plant. "Mixed with oxygen, as carbon dioxide, it was always present, in the atmosphere and in rain-water,'and the supply of it was being continually added to by the respiration of animal life and the processes of combustion. Water, containing hydrogen and oxygen, was indispensable to plant production. Nitrogen, which constituted about three-fourths of t the atmospheric air, was the most expensive item of plant food. It was called the regulating element in this connection, as it controlled the power of assimilation by plants of food'up to the limit of their capacity. Phosphoric acid was the moat important of the mineral or soilfertile foods. Jit was a compound of * phosphorus and. oxygen, which, in fertilisers, was always found in combination The most commonly known medium of phosphoric acid was sold as superphosphate, in varying grades. USES OF LIME. " Y

■• " In considering the place of lime in •productivity it was not contended that all was known in reference to plant foodj there were function that were only partially-understood. By some authorities lime was held to be a'definite food/ whereas others diet not take this view. However, although there was this difference of opinion, it. was clear that lime was essential in the soil to plant growth generally. It was called a physical agent for improving soil texture. It made the clay soils more friable and less tenacious; it made peat soil sweetef, and sandy soil more cohesive. It was 'a compounding element in which practically all fertilisers Ayere used when given to the soil, except in the case of basic slag. Lime must, not be depended oh as an all-sufficient plant food; but it increased the available amount of potash and nitrogen already in the soil. NITROGEN AND POTASH.

Nitrogen, as a source of soil fertility, was the most easily exhausted of all plant foods. To replace the nitrogen taken from the soil, various nitrogenpus manures were utilised. Blood and bone manure was one which contained from 3 to 8 per cent, of nitrogen; sulphate of ammonia, 20 to 24 per cent.; nitrate of soda, about I£s per, cent. Blood-and -bone was . slow-acting, and had to make a chemical change before it became available to plant life. The two other manures . mentioned were quicker acting; and the nitrate of soda did not exhaust the lime content of the soil as much as sulphate of ammonia did.

Concerning potash, Miv Parker said that plants Varied very much .'in their, need of it. After sowing potash, very 1 little difference, if. any, would probably .be found in the grass; but if it was used for potatoes or other root crops, a distinct difference would be noticed, beeai/se it contributed to the making of sugar, starch and fibre. The most used form of potash in fertiliser was, the sulphate, containing about 52 per cent, of pure potash. Muriate of potash contained about 60 per cent., and kainit* about* 12 per cent. Wood ashes had a very small potash content, ranging from 1 to 5 per cent,., and was not t as important a fertiliser as it had been considered in the past. Coal ashes were quite useless as a source of pot- ' ash.

CHEMICAL CONSTITUENTS OS WHOLESALE SCALE. {

In order to show the amount of food taken .by plants from the soil and the atmosphere, Mr Parker quoted some interesting figures. One-thousand pounds of meat represented the removal by fodder of 20 lbs of nitrogen, 25 lbs of phosphate, and 1J lbs of potash. A hundred bushels of wheat accounted for 1131bs of nitrogen, 103 lbs of phosphate, and 30 lbs of potash. A hundred tons of potatoes removed 1060 lbs of nitrogen, 800 lbs of phosphate, and 1600 lbs of potash. These figures were'significant, because they shtiwed ' that replacements must be made to make up for the big drain which these products caused on the soil. The returns of produce exports in 1924 showed'the following amounts of chemicials taken frbm the. soil to be used in tljeir make-up:—Meat, 3126 tons nitrogen, 3908 tons phosphates, 274 tons potash j > wool, 4146 tons nitrogen, 120 tons phosphates, 4448 tons potash 8985

tons nitrogen, 6250 tons phosphates, 273-4 tons-potash; cheese, similar figures to butter; totals, 23,328 tons nitrogen, 15,255 tons 9133 tons potash. The replacement of these principles was a very serious problem, and one which affected the welfare of the community at large. TILLAGE, BACTERIA AND OTHER FACTORS. Soil fertilising, and the replacement of lost constituents, comprised only a portion of the business of making the soil productive, a great part of which depended on the work of the farmer or the gardener in the tillage of the soil. The ground must be worked well and repeatedly to make the plant food available, and in a form in which it would make the plants grow. A soil that contained clods as large as' the hand was not suitable as a seed-bed for small seeds. Capillary attraction was an important factor in plant growth, enabling moisture to rise and meet the small fibrous roots and sustain the growth. Bacteria also formed one of the important features of plant life; the soil must be alive. There was an acid soil which was called a dead soil, and it was useless to many plants. Some growths, such as rye, preferred an acid soil, but most plants liked a sweet soil, vvith bacteria working in it. Plant food, in order to be useful, must be available during the growth of the plant, and it was well |o remember this in the ease of crops which had a growing period of only three, six or nine months. Thus the solubility or useability of a fertiliser must be takeu.into account; This was'particularly important,in top-dressing, where copious rains might carry away the active principles to a depth greater than the lowest roots could reach. The fertiliser should be in a soluble form to enable the roots to grow from its use. It was' a.recognised fact that all plants required a' definite -proportion of phosphoric acid, nitrogen and potash; and no aboundance of the one constituent would make up for the lack of the others or either'of them; there must be (he correct combination of plant foods. Plants, varied in their requirements'.

It. was important to bear in mind the depths to which fertilisers penetrated. Basic slag did not penetrate far —only from one to two inches; ammonia, compounds went down from three to four inches; nitrates penetrated quite deeply; phosphates not; more than eight inches, and potash from five to six inches. These particulars had % bearing on the type of plant that was being raised. ■ It was rather, surprising, said Mr Parker, how"little of actual plant food 'there was in farmyard manure. This was rather a soil improver or conditioner than a food. The very best of it contained less than 2 per cent, of any of the essential elements of plant food;, and its content of these substances — phosphoric acid, nitrogen and potash—only ranged from 0.34 to 1.63 per cent. However, as a soil improver and conditioner to set the bacteria of the earth working, it. was,splendid, and that was its value. It was an improver as, possiblv, lime was. WHAT TO USE. Mr Parker then gave some simple directions for general manuring, which should prove of value to farmers and gardeners. For the former, he stated that a good serviceable stock mixture was one composed of five parts of superphosphate, five of bonedust, two ox sulphate of rpotash, and two of nitrate of soda. This would give 'the proportions of phosphoric acid 14.9 per cent., pure potash 7 per cent., nitrogen 4.3 per cent. For, those who were concerned with the garden, the fertiliser ,cqu!d be used in the dry form at the rate of two tablespoonfuls t:o the square yard and worked into the soil, and nitrate of soda could be used afterwards if required. It might be more; convenient to use a liquid fertiliser, in which case to four gallons of water there must be added 1| oz., of superphosphate, \ oz. of sulphate of potash, and \\ oz. of nitrate of soda. This mixture couid be used with safety on almost-any kind of land to be found in local gardens.

■ Ab the conclusion of Mr Parker's remarks, which had been followed with elo.ve attention, appreciation, was expressed by loud applause, and on the motion of Mr F. H. Hudson he was accorded a hearty vote of thanks for an interesting and able address.