ANALYSIS OF SOILS.

Southland Times, Issue 19540, 2 May 1925, Page 14

ANALYSIS OF SOILS.

SOME ADVANTAGES. SAVES MONEY AND LABOUR. The greatest advantage of having an analysis of the soil made is in the saving of money and labour spent on buying and applying constituents which are unnecessary or are already present in sufficient quantity. An analysis will show whether the elements of fertility present in the soil are in an available state or whether it is necessary to give the plants extra help until they have become established. To be of real help an analysis should show the percentage which are probably available for. plant food in the near future. A grower does Hot require to know how much unavailable wealth he has in his soil. For instance, it is well-known that potash may be present in large quantities, and yet the plants may show signs of potash starvation; the same remark applies to phosphoric acid. It has been established that the roots of plants exude acid which,. acting on the elements of fertility in the soil, renders them soluble and fit for plant food. In making an analysis the total potash or phosphoric acid is first ascertained then these results are acted upon by an acid, and so much as remains insoluble is considered to be combined or tied up and not immediately available to the plants. The percentages that are soluble in these tests are those that are probably available for plant food in the near future. Every chemist is not capable of making a soil analysis, and more especially a soil analysis for a market grower. Only those who are specialists at this kind of work are qualified, since soil analysis is becoming each year more and more recognised as a necessary part of the season’s routine.

WEIGHTS OF DAIRY CALVES INTERESTING FIGURES. The weights of the dairy calves born in the herd of the Missouri Agricultural College have been taken for the past 12 years, and present quite an interesting study. These weights show that the Jersey calves are the smallest, weighing on an average 551 b; the Ayrshire second in weight, with an average of 691 b; the Dairy Shorthorn third in weight, with an average of 731 b; and the Friesians are the largest by far, with an average of 901 b. It was found, further, that (he Jersey female calf averages 531bs at birth, while the male averages 581 b at birth, the female Ayrshire averages 651 b at birth and the male averages '73lb; the difference between the male and the female Shorthorn is but 11b, but the female Friesian weighs 881 b and the male 931 b. The weight of Guernsey, average of both sexes was 711 b, and the average of the brown Swiss, 1001 b. The variation was' considerable in these calves, being as much as 301 b to 801 b in the Jerseys. There was considerably more variation , however, among Jerseys than

among other breeds, which is undoubtedly ■due to the siza of the mothers. It was found that the weight of the Jersey calf at birth was 6.5 per cent of the weight of the mother, the Ayrshire weighing 6.9 per cent, of the dam, the Guernsey 7.2 per cent.- of the weight of the dam, the Shorthorn 6 per cent, of the weight of the dam, and the Friesian 8 / per cent, of the weight of the dam. IX DISEASE; THE ANIMAL AND THE PLANT. There are a number of important aspects wherein the disease of plants differ from those of animals and man, and are more difficult to handle. The most important dif-ference-of all perhaps, is the relatively small amount of help that the plant doctor gets from his patients. Animals and man frequently give themselves a lifelong cure of a disease by having it once; such permanent resistance is built up by an attack of smallpox—or its artificial shadow, vaccination—and is termed “acquired inynunity.” So far as is known, says the Scientific American, in giving an abstract of an address by V. 11. Blackburn at Toronto, plants never acquire immunity and succumb to a second, or third or twentieth attack of a disease as easily as they do to its first onset. It is true that a plant may be naturally immune from the beginning, just as some fortunate individuals in human society are immune to some disease from birth. But even in such naturally immune plants, as' well as in those more readily afflicted, resistance to attempted invasion on the part of the disease-prQducing parasite, is limited to a small part of the plant tissues. The struggle takes place within the confines of a few cells. This is due largely to the absence of anything like a blood circulatory system in plants. Plants sap flows only one way or at least does not flow in a closed circuit, as does blood in animals. The more perfect circulatory system of animals permits all parts of the body *to manufacture resistant substances, like anti-toxins, which are then delivered to the fighting front by the transportation lines of tbe blood system. These two circum-

stances, inability of plants to acquire immunity -by one attack of a disease and their hick of a circulatory system, render unlikely the development of anything like vaccination or serum therapy for plant diseases, and force us to fall back on the selection and breeding of plant strains with natural immunity, supplemented with spraying and other treatments to kill the diseaseproducing organisms as they alight on the leaves and stems of the plants. There* are three principal modes of attack employed by the parasites that cause plant diseases. They may get in through accidental wounds, as corn smut does to a large extent; they may go in through the breathing-pores or stomata, like wheat rust, or they may actually bore or push their way in through the unwounded plant skin. The first two methods are employed by both bacteria and fungi; and the third is used only by fungi. It has long been a riddle how a fungus, which is in the beginning a mere slender white thread, can push its way through the relatively, tough skin. Early theories, which hold that the fungus was attracted by some chemical substance exuded by the plant and in turn used chemical means to dissolve a hole through which it might pass, are now in abeyance. It seems more likely, in the light of recent investigations, that the affair is simply mechanical from beginning to end. The fungus thread seems to glue itself to the fated spot by means of a kind of gelatinous substance, while the central part of the thread pushes a hole through exactly like a shoemaker’s awl. Once inside, the fungus may .be virulent enough to kill the tissues and made a meal of them, sucking out part of their nutriment, or the tissues may turn at bay and fight. Their resistance may be physical and consist of laying down a layer of cork or other tough, impenetrable substance against the invader; or it may be chemical, meeting the poison attack of the fungus with a poison counter-attack. Sometimes this struggle is so bitter that both fungus and invaded tissue kill each other.