POTASH AND LIME.

Waikato Times, Volume 104, Issue 17492, 28 August 1928, Page 11

POTASH AND LIME.

EFFECT ON SOIL AND FOOD ESSENTIA!. IN NEW ZEALAND. LECTURE BY DR. H. E. ANNETT. The relative value of potash and lime to the soil was detailed, in the third of his series of lectures on fertilisers, delivered before the Waikato Dairy Club at Hamilton last night ny Dr. H. E. Annett. The chair was occupied by Mr A. E. Missen, who commented on the very great interest which Dr. Annett's lectures had created and the very useful information which he had given those who had listened to him.

Value of Potash. In opening, the lecturer stated that in dealing with potash he was on rather indefinite ground, as the effect of the use of potash was not usually very obvious to the eye. The average man usually judged the effect 01 manures by what was visible to the eye, and this difference had to be at least 20 per cent, before he was able to discern it. Nitrates and phosphates usually gave this increase, whereas potash did not. They had, therefore, to look in other directions for the benefits of potash. In the first place It gave a better general health to the plant. There were many diseases which were prevalent in potash-starved plants. Potash toned up the plant and gave it a vigour to fight against attacks of disease. It also had the effect of stimulating the production of starch and sugar in the plant. For all those crops which produced starch and sugar, such as potatoes, mangels and beet-sugar, potash was very necessary. It was also particularly necessary for the growth of clovers. It was very important that plants with a healthy growth should be produced, for if unhealthy food was fed to animals it was quite probable that the animals themselves would suffer. Most of the recent investigation work done in relation to feed and its effect on the animal had been done with phosphates and lime, but little attention had been paid to potash. He wondered sometimes if, in view of the amount of mineral matter taken from Waikato land in a year through the milk, they were not neglecting too much this question of potash. It was, he thought, necessary to add J ovft. of potash salts to the acre on pastures which fed dairy cows. He had good reason to doubt the statement that New Zealand soil was not deficient in potash. On light and peaty soils he thought they would find many cases in whicli potash was deficient. In the first few years after a bush burn there should be no shortage of potash, but after years of cultivation and leaching by rains there became a deficiency. Trials were being conducted with potash at Taupiri, and ho was very surprised to see (he effect, which was almost as marked as that of nitrogenous manures. Early Research. The lecturer said the effect of potash was realised as far back as 1760, when wheatstraw was burned in England and sold as a top-dressing. About 80 years ago, at Rothamstead, it was shown that potash was an essential manure for plants and that woodashes were rich in potash, About 100 years ago there was a very large export of nitrate of potash from India. This was won from the soil. About half a century ago large nitrate of potash ■ deposits were found in Germany, which were the result of the drying up of inland seas. The Germans, prior to the war, spent £IO,OOO a year in America in advertising the benefits of potash salts, and by the time the war broke out these potash salts had become so essential to the American agriculturist that America's entry into the war had an immediate result in putting up the price of food. America during the war spent £IO,OOO- - in research work to try and get potash from the soil, without success. In England the research stations had found that for a number of years it was possible to carry on the functions of potash with common salt. It was also found that the Dead Sea was a veritable mine of potash salts. The Italians had recently discovered thai the rocks of the earth could be split up so as to give potash salts in an economical form. The war, thereforehad given the world great stimulus to scientific work, particularly as regards fertilisers. Detailing the various potash manures on the market, the lecturer said that wood ashes contained about 5 per cent, of potash, whereas coal asties were practically valueless. There was synthetic nitrate of potash coming from Germany which, contained 14. per cent, of nitrogen and 47 per cent, of potash, so that it was practically all food. There was also nitrophosca, which was an all-round manure supplying nitrates, phosphates and potash. The cheapest of the potash manures was undoubtedly 30 per cent, potash salts. Potash salts and cer-tain .other forms, however, contained impurities, and sulphate of potash was better for potatoes, though Kanit was better for mangels. For the farmer who knew nothing of chemical analysis .it was as well to know that kanit contained only 14 percent, of potash, sulphate of potash 48 per cent, and potash sails 30 per cent. Liming the Soil. Dealing with the practice of liming .the soil, Dr. Annul I said that lime could not be considered a plant food in the same way as nitrogen, phosphates and potash. It was necessary in the soil, however, especially on dairying country. To replace the lime taken out of the soil by a cow giving 2401 b oC milk a dressing of 3 cwt. of limestone per acre was necessary. The loss was, however, not all through the milk. A growing cow took out a lot of liine for the formation of its bones. Drainage also took out, a considerable quantity. These big losses were increased where there was a very heavy rainfall. New Zealand soil was deficient in lime owing to its open nature and the heavy rainfall. A certain amount of this Jime was made up by the use of superphosphate and basic slag, which gave almost half their weight in lime. Half the nutritional diseases were caused by a. deficiency of lime. Animals on land with a deficiency of lime had much frailer skeletons than those on welllimcd country. One of the functions of lime was to prevent acidity in the soil. On arable land it also allowed cultivation to be carried out much more easily. Actual experiments at Rothamstead had proved that the draught of a plough was 20 per cent, less on land that had been limited. Another function of lime of great importance was that it released potash in the soil and produced good growth oC clovers. Sulphate of ammonia tended to make the soil acid. ■ This could he rectified by the use of lime. Authoritative opinion nowadays was that sulphate of ammonia should not. lie neglocfod in treating the soil, but that rectification should he ' effected by treatment with lime. There was ample evidence to show thai the application

of lime would prevent many anima! diseases. Limestone, ground very fine, was probably the best form of lime to apply and 10 cwt. to 1 ton per acre should supply the requirements of most soils. Qmcklime and slacked lime took longer to distribute themselves through the soil. The speaker went on to say that the production of these fertilisers was getting more and more every year into the hands of big combines. The tendency of these combines was to put out finely concentrated manure containing a variety of plant foods so that they could be sent to any part of the world at the cheapest cost.

On the conclusion of his address Dr. Annett answered a large number of questions and was heartily thanked for his lecture.