ures. Lawes and Gilbert, in their famous English experiments, 

 have raised wheat for forty years continuously on their plots, and 

 some have received. absolutely no manure in all this time. The 

 following figures show the natural capacity of their soil : 



Bush. 



Wheat average for 40 years, no manure, 14 



" " 32 " " 13^ 



7 " " 15^ 



3 



18 



" " 4 " " 255^ 



The first two cases are on the same field, the others repre- 

 sent results on different parts of their estate. The average yield 

 of straw for thirty-years was 1,125 poi^i^ds. 



Taking the experiment plots on our Experiment Station 

 farm and I find that in 1885 we produced on the plots having no 

 manure 47^ bushels sound corn, weighing 40 pounds per 

 bushel ; 27^ bushels soft corn, weighing 34 pounds per bushel ; 

 and 3,246 pounds of well cured fodder. The yield of oats on 

 th^ same land was S3/^ bushels, and 1,900 pounds of straw, and 

 the past year the yield of hay was 3,600 pounds. These cases 

 are sufficient to show that soils have considerable producing 

 power when left unmanured. This is accounted for in the fol- 

 lowing way : All soils fit for agricultural purposes contain a con- 

 siderable amount of plant food ; for example, on the plots above 

 mentioned, where wheat had been produced for forty years and 

 no manure had been applied, there was in the first nine inches 

 of the soil 2,000 pounds of nitrogen per acre. Plots adjoining 

 these and cropped the same, but which had received annual 

 dressings, showed much more. One plot which had received four- 

 teen tons of manure annually had in its top nine inches 4,000 

 pounds of nitrogen. A soil analysed by the Department of Agri- 

 culture showed 4,957 pounds of nitrogen 1,567 pounds of phos- 

 phoric acid, 17,429 pounds of potash per acre. If we compare 

 this large quantity with the comparatively small quantity taken up 

 by good crop we shall see that there is enough for a great many 

 crops, but plant food may be present in vast quantities, and yet 

 not be available to the plant. This brings us to a new classifi- 

 cation oi plant food, namely, available, that which plant roots can 

 pick up and use for the growth of the plant, and unavailable, or 

 that which is insoluble, so that the roots fail togather in any part of 



8 



