7 26 



potatoes, that require both nitrogen and potash as a manure, nitrate 

 of soda gives quite as good results and is much cheaper. Nitrate 

 of potash is too dear to be used much as a manure. 



POTASH MANURES. 



Potash is one of three main elements that enter into the food 

 of almost all plants. It is found in large quantities in the ash of 

 root and leguminous crops ; more than the half of the ash of 

 potatoes is potash, varying from 55 to 60 per cent. The crops that 

 are most benefited by the application of potash are legumes, which 

 require a liberal supply. Potash for agricultural purposes is 

 principally obtained from the deposits at Stassfurt, in Germany. 

 The chief potash salts used as manures are kainit and the double 

 sulphate of potash and magnesia. Kainit contains from 12 to 14 per 

 cent, of potash. The following is an analysis of a fair sample : 



Moisture ... ... ... 3-21 



Water of combination ... ... io'4i 



Potassium sulphate ... ... 2 4'43 



(equal potash i3'2o) 



Calcium sulphate ... ... 3' 13 



Magnesium sulphate ... ... I 3'^3 



Magnesium chloride ... ... 1 4'S4 



Sodium chloride ... ... 29*59 



Insoluble ... "86 



lOO'OO 



The double sulphate contains about 50 per cent, of potasl 

 Most soils contain a good percentage of potash from 'i to 3*0 per 

 cent, and will average about '2 per cent. Most of the soils that 

 I have analysed in Western Australia contain less than 'i per cent, 

 and very few over ~2 per cent, of potash. The soils in this country 

 being lower than most other countries in potash, this should be 

 taken into account when applying manure, and more especially where 

 potatoes are grown and chaff sold oil the farm, or otherwise the land 

 will become too poor in potash to produce goodcrops. Potash is easily 

 fixed in the soil, and various soils have different powers of retaining 

 or fixing it. The clay soils have the greatest power, peaty soils 

 less, and sandy soils the least. This fixing is accomplished by 

 chemical double decomposition, whereby the soil forms insoluble 

 Compounds with potash. 



Proi"e.or \Yay found from '00003 to "00031 per cent, of potash 

 in drainage from arable land. Potash is not a manure that should 

 be applied alone, but in conjunction with some other manure, such 

 iiperphosphates or farmyard manure, and will then give sur- 

 prisingly large crops. The quantity generally used is from one to 

 two c\vt. of the sulphate of potash and live to seven c\vt. of kainit 

 per acre. 



I 



