lo Nov., 191 1.] Kamit as a Plant Food and Fungicide. 737 



THE USE OF KAINIT AS A PLANT FOOD AND 

 FUNGICIDE. 



Alfred J. Ewart, D.Sc, Ph.D., F.L.S.; Government Botanist, and 

 Professor of Botany and Plant Physiology in the Melbourne 

 University. 



Kainit is a natural mineral manure which has long been used in Agri- 

 culture as a potash manure, but which, according to recent work, has also 

 other uses. Tn the pure form, the mineral was formerly supposed to 

 consist of potassium sulphate, magnesium sulphate and magnesium 

 chloride combined with si.\ molecules of water (K^SO^, MgS04. MgCU. 

 6H2O). It seems more probable, however, that it really consists of 

 potassium chloride and magnesium sulphate combined with six of water 

 (KCl, MgS04, 6H2O). It is usually, however, mixed with potassium 

 chloride, rock salt and other impurities. The proportion of pota.sh vanes 

 from ID per cent, to 17 per cent., which is equivalent to about 18 per 

 rent, to 30 per cent, of sulphate of potash. The amount of chlorine 

 may be as high as from 28 per cent, to 50 per cent., although an average 

 percentage is about 30. As a general rule, samples containing much 

 chlorine are also rich in potash. To some extent the presence of salt 

 IS objectionable, particularly if the amount exceeds 30 per cent. For 

 such a crop as mangolds, however, the presence of salt is actually an 

 advantage, if not too abundant ; but for many crops, as well as for flowers 

 and fruit trees, the presence of salt in any amount may exercise a more 

 or less pronounced injurious effect. In such cases where a supply of 

 potassium is needed and co.st is less important, simple potassium salts may 

 be used, such as the sulphate or chloride ; and, on a small scale, the more 

 expensive nitrate. 



The usual application is at the rate of 4 to 8 cwts. per acre ; and, as 

 a general rule, better results are obtained when it is applied to sandv. 

 calcareous or humus .soils, than when it is used on clays and loams. To 

 get the best results the soil must contain a sufficiency of lime, and in 

 pastures the effect is more noticeable on the quality than on the quantity 

 of the herbage. Naturally, it would be little use applying it to a soil 

 already sufficiently rich in potash, and this is best told by actual trial. 



Crops which have specially high pota.sh requirements are potatoes, 

 mangolds and other root crops, carrots, onions, fruits and all kinds of 

 leguminous crops, peas, beans, clover, &c. For grasses and cereals potash 

 is usually less necessary, but recent exj^eriments in the United States 

 showed that the application of a mixture of phosphates and kainit (juad- 

 ruplcd the yield (jf hay, as compared with long unmanured plots, and its 

 use was found to result in the production of a greater yield of marketable 

 potato;^s than the a])plication of any other forni of potash. On the 

 other hand, some experiments carried out in Germany showed that when 

 kainit was applied to the soil in the form of a heavy dressing befor.- or 

 ;ifter planting, it appeared to exercise an unfavourable infiuencf upon the 

 (leveloimiicnt of the skin of potatoes, which would probably affect their 

 keeping (lualities and resistance to disease. Its use was not, however, 

 found to produce any [xrceptible effect on the amount of potato scab, 

 {■ixperiments in tiie south of the United States showed that kainit was mori^ 

 costly as a fertilizer for cotton than chloride of potassium, whereas experi- 

 ments in Fngland, near Leeds, showed that the finest malting barley was 



