68 3 



phosphate; 34.', M>s. of potash, equal to 245 Hs. of kainit; and 40], His. 

 of nitrogen, eq'ual to j^j il.s. of sulphate of ammonia. 



In the case of potatoes, a crop of six tons per acre would 

 abstract 134], Ibs. of mineral matter, containing 20 Ibs. of phos- 

 phoric acid equal to 145.', Ibs. of superphosphate ; 74 Ibs. of potash, 

 equal to 528.', Ibs. of kainit ; and 33], Ibs. of nitrogen, equal to 

 107], Ibs. of sulphate of ammonia. 



Thus it would not be advisable to follow a wheat crop with 

 another nitrogen-loving crop without giving it a liberal supply of a 

 nitrogenous manure ; nor to follow potatoes with a crop that needs 

 potash and phosphoric acid without giving a good supply of both. 

 I have already stated that a soil may contain twenty times more of 

 a certain plant food than any plant requires, and yet that soil may 

 be barren. The reason for this is, that it is in combination with 

 other substances that are very insoluble, such as potash in combin- 

 ation with silicates. The plant has not sufficient power in itself to 

 decompose them, and the actions of the disintegrating agents, such 

 as carbonic acid, water, etc., are too slow for the immediate 

 requirement of the plants. If it were not so, the whole, 

 or nearly the whole of the potash and phosphoric acid would be 

 lost to the soil in one year. Ploughing the land assists greatly in 

 the disintegration of the soil and in freeing the potash and phos- 

 phoric acid by exposing fresh surfaces to the action of oxygen, 

 carbonic acid and water. A manure may also be in such a physical 

 state as to be of no use to the plant. A bone manure is a good 

 manure \vhen the bones are ground fine or are dissolved. If bones 

 in pieces were put into a soil with a crop of wheat that is entirely 

 dependent on the bones for its supply of phosphates, it would 

 simply die off, as it could not obtain enough phosphoric acid from 

 the bones to allow it to live. Or another case which may be more 

 to the point, if raw mineral phosphates were used in a tolerably 

 line state, the result would be that there would be either no crop, 

 or one not worth cutting. This does not include Thomas' phos- 

 phate manure. The mineral phosphates to be of any good would 

 require to be ground extremely line, so that the different solvent 

 agencies could have a greater surface to act on. At the best they 

 would prove unsatisfactory. It is false economy to manure the 



f round, the crop is what should be manured in high class farming, 

 [amiring the ground is nor only costly and wasteful, but requires 

 a very long purse and a great deal of patience, and in the end is 

 unprofitable. Give to the crop what it needs so that it can make a 

 rapid and healthy growth, and let next year's crop look out for 

 itself. Xo crop can take all out of the soil', so there is bound to be 

 some left for next year. 



The soils derive their phosphoric acid and potash as well as the 

 other mineral constituents, from the rocks from which they 

 originated, by a process of disintegration and denudation. The 

 different rocks contain different amounts of mineral matter tit for 



