THE FARMER'S MAGAZINE. 



425 



PHOSPHATE OF LIME. 



BY CUTIIBEET W. JOHNSON, ESQ., F.E.S. 



It is very true that our forefathers made many 

 grave yet ludicrous mistakes in regard to artificial 

 manures ; that they viewed with suspicion all 

 novel dressings for their crops, and ridiculed those 

 theoretical farmers who dwelt in cities — fellows 

 who were merely members of the legal or medical 

 profession. This was certainly the case — was per- 

 haps the natural course of things. It was only at 

 the commencement of the present century that the 

 practical agriculturist began to mingle science with 

 his rural inquiries — found out for the first time 

 that grave philosophers might give him material 

 aid in his difficult labours. The tardiness of this 

 discovery is the more remarkable ; since, before that 

 period, almost all improvements in tillage came from 

 those who were not educated as farmers — from 

 men who now and then suffered their enthusiasm 

 to carry them too far ; it was so with the great 

 Tull, who was a barrister of Gray's Inn. When 

 that great friend of agriculture had discovered the 

 advantages of his horse-hoe husbandry, he nearly 

 arrived at the conclusion that all manure was need- 

 less. It is most amusing to read TuU's denuncia- 

 tion of dung, and his wonder at " delicate palates 

 eating their own and their beasts' ordure, together 

 with all sorts of filth and nastiness, a tincture of 

 which those roots must unavoidably receive that 

 grow amongst it." Tull's want of chemical know- 

 ledge was well and amusingly rivalled, when, about 

 twenty years since, the use of bones dissolved in 

 sulphuric acid was first suggested by Liebig. The 

 advised application of sulphuric acid to the soil 

 was forthwith denounced and ridiculed in every 

 possible way. The very bones to which the mine- 

 ral acid is now so extensively applied, had long to 

 encounter the same opposition. There are yet 

 men, I am told, in Sheffield, who are old enough to 

 remember the time when the Yorkshire farmers 

 were paid for carting away the refuse bones and 

 ivory turnings of the Sheffield knife-makers. It 

 is refreshing to refer to these bygone times; since, 

 when we compare the knowledge of those days with 

 our own, we may be cheered on by the reflection 

 that the onward flow of knowledge has never yet 

 given any indications of being stayed. 



A recently-published series of researches, by 

 Professor Vo'elcker, on the phosphatic manures, 

 appears in bold relief indeed to the state of our 

 former knowledge, to which I have referred, of not 

 yet a quarter of a century since. This reference 

 we may the more profitably make, because now is 

 the time when the manures for our root crops are 

 generally employed, and almost all these have 

 phosphate of lime in some form or other for their 

 chief base. In this remark I am well supported 

 by Professor Voelcker, who observes {Jour. Roy, 

 Ag. Sac, vol. xxi. p. 350), when speaking of the 

 phosphatic materials used in England for agricul- 

 tural purposes : " Manure manufactories are now 



spread over the length and breadth of the country, 

 and in all thpse works the staple product, under 

 whatsoever name it may be sent out, is in reality, 

 in nine cases out of ten, superphosphate of lime. 

 The consumption of this kind of manure, large as 

 it is at present, is increasing every year, and is 

 likely to increase for years to come. It must not 

 be supposed that the large demand for phosphatic 

 manures is the result of extraordinary exertions on 

 the part of manure merchants, or is due to a pre- 

 vailing, and it may be passing, faith in this class 

 of fertilizers. It rests on the universal experience 

 of farmers that no description of manure repays a 

 judicious outlay so well as this, especially when 

 applied to root-crops. AVhilst other kinds of fer- 

 tilizers have been tried on a large scale, and not 

 been found to realize the expectations raised, 

 superphosphate and similar phosphatic manures 

 have maintained a firm hold in the good opinion of 

 the agriculturist. Far be it from me to undervalue 

 the great utility of Peru\'ian guano, nitrate of soda, 

 and nitrogenous manures. These are excellent 

 fertilizers for wheat and corn-crops in general ; but 

 considering the circumstance that a good root-crop 

 lies at the very foundation of an improved system 

 of agriculture, and that this crop is more signally 

 benefited by phosphates than by any other fertiliz- 

 ing constituent, 1 believe the farmer is right in 

 attaching the highest importance to phosphatic 

 manures. At all events, he has found by expe- 

 rience that in most cases in which it is deemed de- 

 sirable to make up a deficiency of yard-manure, it 

 pays better to purchase superphosphate and similar 

 manures for the root-crop than to buy nitrogenous 

 manures for the white crops. It is certainly re- 

 markable that whilst the direct application to the 

 land of nitrogenous constituents has been by some 

 considered useful only in special cases, and by 

 others superfluous or even undesirable, nobody 

 has ever expressed any doubt as regards the eco- 

 nomical benefits that generally attend the use of 

 phosphoric acid ; whilst nitrogenous manures in 

 the case of some crops, such as peas and beans and 

 clover, have been found even to be injurious, every 

 kind of produce has been more or less benefited by 

 the direct application of phosphates in an available 

 condition. Whereas ammoniacal salts and other 

 purely nitrogenous fertilizers, when applied alone 

 to swedes, turnips, and probably other root-crops, 

 have, generally speaking, failed to increase the pro- 

 duce, the exclusive use of soluble phosphates has, 

 in almost every instance, largely benefited these 

 crops. Again, we can increase the proportion of 

 nitrogenous constituents in the soil by other means 

 than by their direct application in the shape of 

 manure. Thus, after a good crop of clover, I have 

 found that the amount of nitrogenous matters in 

 the soil is very much larger than it was before the 

 clover. If, therefore, we can succeed in growing a 



