XX XVI 



INTRODUCTION. 



poor results. Nature protects herself, and the farmer s capital will be exhausted long before he has so 

 exhausted the soil of phosphoric acid, that a good farmer might not render the same soil highly pro 

 ductive. an:l that, too, without the application of a single atom of phosphoric acid. 



It is true that it is often the cheaper method of renovating such soils by the direct purchase of 

 bones, guanos, or other manures which contain large quantities of phosphoric acid ; or, what is some 

 times cheaper still, by the purchase and consumption of oil-cake, cotton-seed cake, &c. As long as ice 

 can obtain good crops of clover, we need not apprehend any deficiency of phosphoric acid. Under such 

 circumstances there is little hope that an application of phosphoric acid to any of the cereals would be 

 attended with any great benefit. 



Now, all agree that phosphoric acid is more likely to be deficient than any other ash-constituent of 

 plants; and if the above argument is correct and it is sustained by many well-known facts it follows 

 that, in the majority of cases, there is no necessity for the direct application of mineral manures to the 

 cereals. Bat the cereals need manure of some hind, the average yield being not half what it should be. 



We have shown that so long as we can grow good crops of clover, the soil contains in an available 

 condition a sufficient quantity of mineral plant-food for the production of the largest crops of wheat. 

 We do not, therefore, need a direct application of mineral manures. But we need manure of some kind. 

 We must, therefore, look among the organic manures for the particular ingredient which is required. 



Organic manures are divided into two classes, carbonaceous and nitrogenous. It must therefore 

 be a carbonaceous or a nitrogenous manure, or both, that we need to enrich our land for wheat and other 

 cereals. 



It might easily be shown that we do not need carbonaceous matter for the growth of wheat. On 

 soils, as we shall presently show, where we have been in the habit of ploughing in clover, there can be 

 little doubt that carbonaceous matter is in excess; and on all soils, if it was carbonaceous matter that 

 was needed, nothing would be easier than to supply it in abundance, and at a cheap rate. If it is not 

 carbonaceous matter that we need, it must be nitrogenous matter. 



Organized nitrogen in decaying ultimately forms ammonia, and it is in this state, or as nitric acid, 

 that it is generally taken up by plants. In speaking of nitrogenous matter, therefore, it will be more 

 convenient to speak of it as ammonia. In enriching the soil for wheat and other cereals, the main 

 object should be to get ammonia. 



We know of no system of culture, or of manuring for the cereals, which experience proves bene 

 ficial, that does not, cither directly or indirectly, furnish ammonia to the soil, either by eliminating it 

 from the organic matter in the soil, or by increasing the capacity of the soil for abstracting it from the 

 air, or dews, or rain, or by growing those plants which have this power, or by the direct application of 

 ammonia in manure. We cannot increase the growth of the cereals without increasing in some way 

 the supply of ammonia. We are well aware that neither the cereals nor other plants will grow unless 

 the soil contains all their ash-constituents in sufficient quantity and in available condition. But there 

 is no practicable and economical method of supplying the requisite quantity of ammonia which does 

 not, at the same time, furnish these ash-constituents in quantity fully equal to the demand of the 

 increased growth of the cereals caused by the application of the ammonia. 



This assertion is based on the experiments of Messrs. Lawes and Gilbert, confirmed as they are 

 by the experience of practical farmers. 



Mr. Lawcs has devoted a large part of his home-farm at Rothamsted, England, for the last twenty- 

 two years to experimental purposes. One field of fifteen acres has been devoted to experiments of 

 different fertilizing substances on wheat wheat having been annually sown on the same land for over 

 twenty years. Another field has been devoted in the same way to experiments on turnips ; another 

 to experiments on peas, beans, and tares ; another to experiments on clover, and another to experiments 

 on barley alone, and in rotation with other crops. On the wheat-field it was found that none of the 

 manuics used increased the yield of wheat to any material extent, unless they contained ammonia. 

 Potash, soda, superphosphate of lime, magnesia, the ash of fifteen tons of barn-yard manure, the ash of 



