DUNEDIN GARDENING CLUB

Otago Daily Times, Issue 21994, 1 July 1933, Page 7

DUNEDIN GARDENING CLUB

The Dunedin Gardening Club met on Tuesday evening, vyhen there was a good attendance, Mr H. H. Hollingworth presiding. Mr R. B. Tennent, of the Agricultural Department, gave a practical demonstration of chemistry in the garden, and stated that there were two conditions of soil — acid and alkaline. An acid soil was sour, and was no good for growing plants, as it was not suitable Tor the cultivation of the necessary bacteria to produce fertility. It required the acidity removed. This was done by the application of some alkaline matter. Lime was an alkali which was used for that purpose. Lime acted in a double capacity, as it not only counteracted the sourness,/ but it also improved the physical texture of the soil. Most local soils were greatly benefited by the application of lime, and where the sourness was very pronounced it was best to use for a manure one of an alkaline nature, such as basic supei - - phosphate or basic slag. There were two forms of lime in general use —carbonate of lime and ground burnt lime. Carbonate of lime was the raw limestone rock, simply ground to <i fine powder. It was much slower in its action than burnt lime, as it depended on the action of the air and the chemicals in the soil to break it down. It was much cheaper than burnt lime, but required twice the quantity. Burnt lime was the limestone rock roasted in kilns and then ground to a fine powder. It should be applied to the surface of the soil and allowed to work itg way down. It acted much more quickly than carbonate. Superphosphate was the phosphate rock from the Islands broken down by the application of sulphuric acid. The acid was sour, and to counteract this sourness as much as possible another process wag employed. It was then known as basic super. ■ Mr Tennent then spoke on manuring generally and the well-known highly-imec-tious disease “ club root.” It was estimated that 25 per cent, of farm-grown turnip crops were lost through the ravages of this disease. For some considerable time his department had made continual and searching experiments, and had tried every suggested remedy. He was working along two lines. One was the production of plants that would be immune from the disease, and the other was to attack the disease itself. The best remedy so far discovered was to lime heavily m the winter, and at sowing time to use either basic slag or basic super, with a view to sweetening the soil as much as possible. This, if not a complete cure, would certainly go a long way in overcoming the disease. All infected plants should be burnt and not left about, as owing to their very infectious nature they would only spread and encourage the disease. The lecturer dealt fully with the mixing of manures. Lime, he said, should not be used in conjunction with ammonia or horse manure, as it caused the ammonia to escape into the air. Where large

quantities of horse manure or decaying vegetable matter were used it was beneficial to dress the soil with lime the following winter. All decaying vegetable matter made humus, which was necessary, but at the same time it tended to make the soil sour. Mr Tennent, in the practical demonstration, showed the effect of the various chemicals and also the effect of lime on soil. At the conclusion questions were asked and answered, and on the motion of Mr J. Passmore a very hearty vote of thanks was accorded Mr Tennent and his assistants.