SODIUM CHLORATE

Taranaki Daily News, 14 October 1933, Page 12

SODIUM CHLORATE

USE ON RAGWORT. DRY DUSTING METHOD. Developments in technique in connection with the application of sodium chlorate in the eradication of ragwort are discussed by Mr. J.. W. .Deem, Director of the Fields Division, in the current issue of the Journal of Agriculture. The merits of spraying and dusting are compared. The dry method, he says, has greatly extended during the past season, and he gives great credit to Mr. W. E. Alexander, of Pio Pio, for the energy and persistency with which he has advocated this system. He considers that this system will continue to expand and that in many cases it will entirely take the place of spraying. The results of tests show definitely that sodium chlorate is still the most efficient and economical to use, he states. Furthermore, it has been proved that where the plants are nearly the flowering stage, or are in that stage, a 2 per cent solution sprayed on is quite strong enough to give 100 per cent of kills. With the dry method the plants are dusted with the powdered sodium chlorate, mixing it with a spreader to get bulk. BROADCAST METHOD. The broadcast method is necessary where land is so badly infested with small plants that practically the whole surface of the land is covered, and likewise where it is desired to give the land a dressing of lime—always provided the work is done when the plants are in the rosette stage, and in any case not later than the end of November. This is important, as the grass burned at this stage has a chance to recover before the dry weather sets in. “An important question crops up here,” says Mr. Deem. “This is whether land so badly infested should be treated with sodium chlorate 'to clean it up. This depends on the nature of the land. If it is hill country and unploughable there is no alternative, but, on the other hand, if the land is ploughable, it should be broken up and put into a good sole of grass, and the ragwort plants treated as they come up. The ploughing and cultivation will destroy most of the existing plants, but there will be large quantities of seed in the land and a number of these seeds will germinate, and it is the plants from these that will have to be treated. Experience has shown that this is the best procedure.” DETAILS OF THE TRIAL. Details are given of a trial carried out in Taranaki during the past season to determine the relative costs of spraying versus dry treatment. An area very badly infested with ragwort was selected, and various treatments were applied on December 19, as set out. The cost in each case was as follows:— (a) One acre, sprayed with a 5 per cent solution—24lb. sodium chlorate at 41d per lb. and labour (8 hours at Is 6d per hour)—£l Is. (b) One acre treated with carbonate of lime and sodium chlorate put on as a top-dressing—scwt. lime at 25s per ton, 281 b. sodium chlorate at 4Jd per lb. and labour (mixing, at Is 6d per hour, and spreading, at Is 6d per hour) —l9s 6d. (c) One acre treated with Nauru phosphate and sodium chlorate —3cwt. Nauru phosphate at £4 5s per ton, 281 b. sodium chlorate at per lb. and labour (mixing and spreading)—£l 6s. (d) One acre treated with basic slag and sodium chlorate—3cwt. basic slag at £5 per ton, 281 b. sodium chlorate at 4|d per lb. and labour £1 8s 3d. An inspection of the area on March 10 showed the following results:— (a) Complete kill, only one plant being found, and a splendid green growth of grass and clover. It was hard to believe the land had been badly infested with ragwort in December, (b) A fairly good kill, probably 95 per cent, but the ground still showed brown from the burning effects of the sodium chlorate. It was noted that a few plants had evidently been missed when topdressing. (c) Much the same as (b), except that there was more growth, and the area was greener, no doubt owing to the fertilising effect of the phosphate, (d) Similar to (c), except that the area showed more growth and was greener, owing to the fertilising effect of the slag. RECORDS OF COST. A further 12i acres of the same farm were treated with carbonate of lime and sodium chlorate at the rate of scwt per acre on March 24, part being applied by machine and part by hand. The 1 machine-dressed area subsequently appeared very clean, but the handdressed portion showed a few patches that were evidently missed. Careful records of cost were kept, and are as follows:— Three tons lime, at 25s per ton, £3 i 15s; 3cwt. sodium chlorate, at 45s per cwt., £6 15s; labour (mixing and spreading), £1 19s; total, £l2 9s (or 19s lid per The importance of thorough mixing when using sodium chlorate in conjunction with a spreader is stressed. The sodium chlorate should be thoroughly incorporated with the lime to ensure that very small quantities of the spreader dusted on to a plant contain some chlorate. Sodium chlorate is obtained in two forms—powder and crystals. Powdered sodium chlorate, as usually sold, contains a considerable number of lumps and large particles, and before mixing with the spreader it is necessary to sieve out these lumps and crush them to the powder stage. DIFFERENT QUANTITIES, For small quantities the required weight of spreader and sodium chlorate may be weighed out and thoroughly mixed, but for larger quantities the following procedure is recommended: Where a ton is to be mixed, or some similar definite quantity, take the amount of sodium chlorate required for the whole mixing and thoroughly mix this with an equal weight of the spreader. When this has been done this mixed material may then be mixed with the rest of the spreader. Mr. Deem recounts the experience of a Waikato farmer, who, having received his sodium chlorate in crystal form, and being faced with considerable difficulty in reducing it to the powder form for mixing with the spreader, hit on the idea of dissolving the sodium chlorate in water and spraying it on to the spreader. He took 21b. of sodium chlorate, dissolved it in 12 pints of water, and sprayed this on to lewt. of carbonate of lime. He reports excellent results, but is of opinion that owing to the better distribution of the sodium chlorate 11b. of that material to lcwt. of lime would have been ample.