814 



THE AOBIOULTURAL JOURNAL. 



the character of a soil what the proba- 

 bilities are. Almost all the potash con- 

 tained in the soil came originally from 

 the wearing down of a mineral called fel- 

 spar, which is a constituent of the older 

 rocks like granite and whinstone, and 

 soils derived directly or indirectly from 

 these rocks will generally contain suffi- 

 cient potash to keep them going, except 

 for specially potash-loving crops like po- 

 tatoes. Such soils are usually clays or 

 clayey loams. But sandy soils, which 

 consist largely of grains of quartz, are 

 almost always poor in potash, since quartz 

 does not contain any. Moreover they 

 have not so much i)o\ver as clays of hold- 

 iu'^ soluble salts in their grip, so that the 

 rain does not wash tliem away, and there- 

 foie any potash they may obtain has a 

 tendency to gradually diminish in quan- 

 tity. iVny soil which contains an abun- 

 dance of decaying organic matter will 

 naturally not be very deficient in potash. 

 There is one rather rciiiar]<able point in 

 connection with sheep-farming which is 

 worth notice, and that is that the grease 

 of wool contains nearly half its weight 

 of potash salts, and in the wool-washing 

 districts of France about fl 00,000 worth 

 is extracted annually from this source. It 

 is therefore to be noteil that on a sheeji- 

 farni large quantities of potash are re- 

 moved from the soil every year in the 

 woo], and that the soil is more rapidly 

 exhausted of this constituent if grazed 

 by sheep than by other animals. 



Wood Ashes. 



There are four substances in use in the 

 Colony which are applied to the soil in 

 order to supply it with potash; these are 

 wood ashes, sulphate of potash, muriate 

 (chloride) of potash, and kainit. The 

 first of these is an excellent manure, if 

 it can be obtained in suffiffcient quan- 

 tity, because in addition to the potash 

 it contains all the mineral constituents 

 of the original plant with the exception 

 of the nitrogen, and of these the chief 

 arc the lime and phosphoric acid. As 

 has already been ])ointod out, the value 

 of a ])otasi) manure must be decided by 

 the amount of potassium oxide it con- 

 tains; !)ut that of ashes varies so greatly, 

 both according to the kind of plant they 



were made of and the soil it was grown 

 on, that it is impossible to give even an 

 average percentage that might represent 

 their value nearly enough for practical 

 purposes. To illustrate this fact, and 

 also that some plants need more potash 

 than others, a few instances are given be- 

 low, showing the amount of ash, and of 

 potash contained in it, obtained from 

 IjOOOlbs. of the dried products men- 

 tioned: — 





Ash. 



Potash. 





lb. 



lb. 





.. H 



4 





.. 134 



14 



Willow wood . . 



.. 38 



21 





89 



4l| 



Oat (grain) 



.. 29 



11 



Maize (grain) . . 



.. 15 



54 



Oat (straw) 



. . 54 



104 



Potato (tuber) 



. . 43 



27 



Sulphate and Mueiate or Potash. 



These are concentrated inannres, tlie 

 former containing about 50 per cent., the 

 latter about 60 per cent, of potash. These 

 are the qualities that have been on sale 

 in the Colony, but lower qualities are 

 made, and a guarantee should always be 

 required in buying. They are at first 

 sight rather costly, but it must be re- 

 membered that in buying them one ob- 

 tains a large (piantity of potash in a 

 small bulk, and hence a great deal is 

 saved in freight. The price of both is 

 nearly the same, so that the potash in the 

 muriate is the cheaper. Some agricul- 

 turists, however, feel a reluctance to use 

 chlorides {i.e., muriates, see Chap. II.) 

 in any form on their crops, as there may 

 be, in some cases, a danger of harming 

 the plant. In the case of tobacco, there 

 is no doubt that chlorides are harmful. 

 Still, the muriate has been largely used, 

 and with success, so perhaps the danger 

 is rather remote. 



Kainit. 



This is a natural mixture of various 

 salts obtained from mines in Germany, 

 containing little potash compared with 

 the other two, only about 13 per cent. 

 Accordingly it takes about 4 tons of 

 kainit to give as much potash as a ton 

 of sulphate, and 4 J tons to equal a ton 



