224 PLANT-FOOD AND AGRICULTURE. 



13tli. Waste of fertility in our land arises from drainage, and 

 the changing of soluble plant-food into insoluble forms. 



14th. Plants require different proportions of plant-food, and 

 different combinations, at different periods of their growth. 



15tli. The presence of certain elements in excess has an influ- 

 ence on the growth and composition of the plant. 



16th. The seed has an influence, in itself, in determining the 

 crop, an influence apart from the presence of a full supply of food, 

 or the climatic features of the season. 



Let us see what are the logical deductions from these proposi- 

 tions. We cannot say that an application of a given quantity of 

 plant-food to a given area of land will produce a given crop, be- 

 cause the crop depends not on the fertilizer which is applied to 

 the land, but on that which is within reach of the crop, and which 

 the crop can appropriate, besides the other questions of variety of 

 seed, and the corresponding habit of the plant which is grown, 

 and the influence of the culture, and the character of the season. 

 We cannot advise the application of a single element of fertility, 

 because the plant must have all the required elements to succeed, 

 and we cannot know which one is deficient, or whether in apply- 

 ing the single element proposed, we are not destroying the bal- 

 ancement of fertility present in the field, or are not applying an 

 excess of this element, which is to be wasteful. Indeed, by the 

 application, of a single fertilizer continuously, as superphosphate 

 of lime, we are certain in the long run to injuriously disturb the 

 balancement of food-supply, and cause in time a deficiency of 

 some other element requisite for plant-food, which we have not 

 supplied. As a matter of fact, we have heard of the use of fish- 

 guano for a series of years, as having completely exhausted a field, 

 notwithstanding the great crops produced by the first or second 

 applications. 



Under this practice of the application of single elements of fer- 

 tility to our land, an erroneous idea concerning manures and fer- 

 tilizers has become popularized. Many, perhaps the majority of 

 our farmers, regard commercial fertilizers as having peculiar and 

 distinct properties from manures, and regard their use as either 

 experimental, or else as fitted only for use in connection with 

 barn-yard manure, or as they express it. as "stimulants." Now, 

 an enlarged common-sense, founded on experience and reflection, 

 must convince that plant-food is plant-food, whether supplied in 

 fertilizer or dung: that a pound of soluble phosphoric acid. 



