THE RURAL WORLD.

Otago Daily Times, Issue 22284, 9 June 1934, Page 3

THE RURAL WORLD.

FARM AND STATION NEWS.

By Rusticus

OTAGO PROVINCIAL SHEEP DQG ASSOCIATION THIS YEAR'S TRIALS. The association has fixed the following locations and dates for the collie dog trials for 1934: Tuapeka.—June 15, 16, and 18. South Island Sheep Do* Association CharapionshiD (to be held at Stratn Taieri).—June 19. 20, 21. and 22. Otego Freezing Season The freezing works throughout Ofcago will cease operations at the end of the present month, and, in expectation of the closure, stock is coming. to hand fairly freely. It is not unusual for the* schedule to show a rise toward the close of the season when lambs are becoming lighter in; supply, and this season there is, of course, the sustained firmness of the Home markets to keep values up. Prices have firmed., even more consistently over _ the latter months of this season,' andgraziers' balance. sheets should be far from unsatisfactory. On an average over the season values have been twice as high; as last year, but the full effect of this im-

provement is to some extent offset by the Jesser volume of stock that has passed through the works. According to the latest statistics, the total number of lambs killed in the South Island up to May 15 •was 633,000 lower than last year, and to this reduction Otago has made a very considerable contribution, although it is probable that Canterbury's contribution has been proportionately higher. Royal Show Venue From opinions expressed in Hunedin by prominent members of the Southland Agricultural and Pastoral Association this week, it would Beem that there is a strong body of opinion in the, southern province .opposed to the proposal to centralise the Royal Show in Palmerston North and Christchurch. The conference of A. .and P. societies in Dunedin this week protested vigorously against the idea, and it is understood that vigorous representations are to be made to the Royal Agricultural Society by affiliated societies in Southland. It is encouraging to find the Otago Agricultural and Pastoral Society seriouslv considering the possibility of k a Royal Show being held "in Dunedin within the next three or four years, particularly as an active step in the direction of secur. ing such an exhibition might have the effect of creating a degree of enthusiasm among members which has not always been apparent. One essential to a Royal Show in Dunedin will be a greatly increased local membership.; Friesian Sale The dispersal sale at the Wairarapa Show Grounds, Carterton, of Mr 0. A. Cadwallader's Ahikouka" Friesian herd attracted a larfle attendance of breeders. The selling agents were Messrs Wright, Stephenson, and Co., Ltd., and the 152 head sold averaged 15 guineas. Among the South Island purchases were the heifer Ahikouka Queen Topsy by Mr W. Marshall (Kaitangata), at 27£ guineas, and the cow Ahikouka Lady Royalist by Messrs J. Robinson and Son (Milton), at 60 guineas. , . SUPERPHOSPHATE AND SOIL ACIDITY By SCRIBA. A recent Australian publication entitled "The Application of Fertilisers to the Orchard and Garden," by R. A. Boyle, M.Sc, A.A.C.1., deals specifically withthe above subject, and states: — Superphosphate quite definitely is not an acid forming substance in the soil. This fact has been well demonstrated at the Rotharasted Experimental • Station. A certain soil there had received 3Jcwt of superphosphate per acre each year from 1877 to 1906, and 3cwt per iicre from 1907 onwards. Samples of the soil were taken in 1927. The total amount of super therefore that had been applied was 105 cwt per acre. The results of the sample tests were as follows- — Treatment. pH Value. No superphosphate 5.35 _ Superphosphate 5.91, i.e., less acid. Note. —A pH value of 7.0 represents a neutral condition. Values lower than 7 denote acidity. Values higher denote alkalinity. The" lower the value, the greater the acidity. This point has also been amply .supported by experiment in Victoria, as the following figures, supplfed by the agricultural chemist, illustrate:—

Item* of Interest to those engaged in agricultural and pastoral pursuit* with a view to their publication in these columns, will be welcomed. They should be addressed to "Rusticus," Otago Daily Times, Dunedin.

Station. pH Values. No. of years. Receiving No Super. Super. Super. Werribee .. 5.7 5.8 15 years. Longerenong 8.4 8.4 17 years. Rutherslen .. 7.8 • 7.9 12 years. The idea that superphosphate does create acidity has probably arisen in the minds of growers chiefly on account of two reasons:— 1. There are certain chemical expressions used in connection with superphosphate which embody the word " acid"; for instance, in 'Americ'a the substance was until quite recently known as " acid phosphate," whilst the content of plant food in superphosphate is frequently referred to aa so much phosphoric acid. The term "acid" in this connection is purely a chemical expression which, does not signify acidity in the soil, or in what ia known as the physiological sense. 2. The repeated use of phosphate or any kind, alone, i.e., without the application of the other two plant foods and most particularly without restoring the human supply or without at least a system of crop rotation, may eventually result in that soil becoming less fertile, and in this case certain weeds which coincidentally may thrive also in acid or worn-out soils, may make their appearance, e.g., sorrel. Such a condition

ig, of course, not due to the superphosphate which has been applied, but to the fact that the possible influence of so many other factors has been forgotten or neglected. Such a soil i fi sometimes said to be " superphospate sick "—just as too much clover in a; pasture might cause " clover taint but which is really to blame, the super and clover or the farmer? ' The above information makes it rery clear that the use of superphosphate will not increase soil acidity, but is more likely to have the opposite effect. Where the soil has an acid reaction, lime is mended to correct the acidity. Next to phosphate, lime is the most important constituent of-the soil, serving to keep the soil in, a sweet condition. MILK THE CHEESE-MAKER'S PROBLEM CAUSES OF CONTAMINATION ■ DAIRY RESEARCH INSTITUTE'S ! WORK. One of the problems which gives perhaps the most trouble and worry to-' a cheese factory manager is the development of acidity at a normal rate in his vats from day to day. Starters are extremely variable at times for reasons which are by no means clear to anyone up to the present, but even when an active starter is available it sometimes happens that it will not grow well in certain particular vats in a factory. Someti'neij one vat out of four or five shows a lengthy delay in acid development, and this is sometimes so serious that a good deal of cheese is of very poor quality, for first-class cheese cannot be made li acid development is not normal. This aspect of manufacture was dealt with at lenfith at the South Island Dairy Association conference on Thursday by Dr Whitehead, bacteriologist of. the Daii'y Research Institute at Maesey College. Milk, he said, which hampred the action of starter in this way had been call.'d "non-acid" milk. Trouble had usually been traced to the milk of one or two suppliers, and many theories had been put forward to account for its abnormality. It had been suggested, for instance,/ that too much caustic soda *iad been used in cleaning the machines —eo much got into the milk that it neutralis3d some of the acid formed by the starter. Bacteriologists had suggested that some germ-forming alkali got into milk and competed with the starter germs, neutralising it. He had thought in the past that the trouble might not be due ro bacteria at all, but might be caused by some abnormality in the milk as it came from the cow. • :

During the past 18 months, however, they had been successful in tracing tne cause of the trouble, and had shown that all the above theories were fallacious. SPASMODIC TROUBLE.

One of the main impediments to making progress on the problem was the spasmodic nature of trouble. When one

started to investigate a case the trouble suddenly disappeared, and a lot of work was usually done with no result. They had been fortunate, however, in encountering a case which persisted for many days consecutively, and their work in the laboratory during the previous years had led to the discovery of methods by which the trouble could be investigated. It was an instance where work done with other objects in view suddenly found its application in this particular problem. METHOD OF INVESTIGATION. The milk of all suppliers which could possibly go into the particular vat where acidity could not be developed was taken separately, and samples were pasteurised and submitted to a "vitality test," all with the same starter. It immediately became evident that one particular milk supply was the cause of the trouble. (The vitality test was simply a curd test with the addition of starter in which acidity determinations were carried out on the whey which drained from the curd. It simply copied the operations in the vat on a small-scale.) This milk would not permit an active starter to develop any significant amount of acid at all. The next point to decide was in what way this milk supply was abnormal. By the methods used in bacteriological laboratory they picked out representatives of the various germs contained in the milk (which, by the way, was fairly heavily contaminated). Then by growing these germs separately in several samples of good quality milk which was known not to hinder the production of acid by starter cultures they determined whether the milk after the growth of the various germs had any markedly different properties. Several of the germs, were shown immediately to have no appreciable effect, but one particular type had exactly the same effect as had been observed in the miik which gave the original trouble. Any milk in which this germ had grown became " non-acid " —very little acid could be developed in it by an active starter culture. It was not necessary that the germ should be still alive at the time the starter was added in order to produce its effect. Once the germs had grown to fair numbers (as it would in uncooled milk overnight), the milk might be pasteurised, or even raised to boiling

point, and yet*it would not permit an active starter culture to develop acid. Contamination of milk on the farm with this particular germ and appropriate conditions (such as lack of cooling) to allow the germ to grow overnight explained therefore in a completely adequate manner the phenomenon of "non-acid" milk in the particular case under investigation. Since the time when they investigated this first case they had been on the look-out for similar cases in order to find out whether the same germ was responsible for all cases of " non-acid " milk. They had seen sufficient cases now to say that this was probably the case. They always. found the same type of germ.

AN INTERESTING POINT. - And in this connection we come to what was, perhaps, the most interesting point. The "non-acid"' germ was itself an acid forming organism not as might have been expected an alkali former. In some instances it formed so much, and that of the milk was used in the raw state for cheese manufacture there was no difficulty in developing acid since the "non-acid" germ itself assisted in the formation of acid. When, however, the milk in which the germ had grown for some time was pasteurised before being run into the cheese vat no acidity could be developed because the germ had formed during its growth some substance in the milk which acted almost like a powerful disinfectant on the normal acid forming germs in the starter. This substance could not be destroyed by any heat treatment of the milk, and there appeared at present to be no way of rendering the " non-acid " milk suitable for making normal cheese. As he had already indicated, it was possible sometimes to get over the trouble to some extent by ceasing to use the pasteuriser and allowing the living " non-acid" germs to assist in the production of acid, but this was a risky procedure from the point of view of cheese quality, since germs which gave bad flavour would ajso be left

alive and the cheese might be of poor quality even though acid production in the vat was normal. ELIMINATING INFECTION. As with all troubles caused by bacteria, the proper way to proceed was to try to eliminate the infection at its source. Where was the " non-acid" germ to be found on the farm?" This was a question which they had not finally answered. They had, however, got some information on the point. It was to be found in ensilage, and where this was being fed the germ would get into the milk unless very clean milking methods were used. They had, however, some evidence that the germ was also found ill small numbers within the udder of certain cows, so that it was present in the milk entirely apart from contamination from outside sources. But the numbers present in the freshlydrawn milk were much too small to cause any trouble in the vat, even if the milk remained uncooled oveimight. CAUSES OF CONTAMINATION. From the evidence at present it appeared that wherever the original contamination arose (be it ensilage or the cow's udder) the poorly-cleaned milking machine wa 8 the place from which large numbers of the germs found their way into the milk. The few germs from the ensilage or udder allowed to multiply in unsterilised machine formed finally a heavy contamination for the milk which passed through the machine at the next milking time. Inadequate cooling of the milk allowed the germs to multiply still further until the milk was able to cause trouble in the factory, even when it was mixed with quite large quantities of highquality sound milk in the vat'. REMEDIAL STEPS. They knew now that it was not _of much use to apply a higher pasteurising temperature to " non-acid" milk. The substance in the milk which prevented the starter from forming acid had already been foi-med in the milk overnight, and no reasonable degree of heat would destroy it. Where the " non-acid " germ was of a type which formed at a reasonable rate itself some temporary relief might be obtained by using the milk in the raw state,

but it was better to attempt to eliminate the trouble at its source,

The factory manager had first to determine which part of his milk supply was at fault. The curd test would not help him here. The " not give a bad flavour, nor did it produce any other recognisable peculiarity in the curd. The " non-acid " milk would certainly decolourise methylem blue rapidly, but so would any other milk containing large numbers of bacteria. The only way in which to detect the abnormal milk was to perform vitality tests on samples which had been pasteurised; in other words, to copy on a small scale the procedure which was followed in the ,vat.

Having forced the supply of milk which was at fault there were simply two points which should have attention on the farm. The milking machine should be inspected and measures should be taken to ensure that it was thoroughly cleaned where necessai'y Secondly, the cooling of the milk should be made as efficient as possible.. Even if numbers of " non-acid" germs get into the milk the prevention of their growth overnight by cooling would mitigate the trouble to a large extent, for they must be present in fairly large numbers before the trouble became apparent. In this connection one wondered to what extent the .cheese makers did suffer from the effect of non-acid milk. There might not be very frequent cases of vats of cheese being absolutely ruined, but there were innumerable instances where vats were slightly slow and just plow enough to prevent the manufacture of the highest quality cheese. There was still a mystery as to why one or two suppliers should get their milk infected with non-acid germs. The work on non-acid milk, however, illustrated well the facts that the daises of the troubles were often found in very unexpected directions, ! and that pasteurisation, although it had served very well, was not a cure-all and did not eliminate the need for extreme care in milk production.