farmers' institutes. 243 



duction notwithstanding the large amount of the elements of fertility that 

 chemists find in them. Statistics also show that the maximum crops upon 

 which I have made the estimates just presented are not being produced. 

 Let us try to find why this is true. It is evident that the quantity of plant 

 food present does not necessarily determine the fertility of the soil. The 

 quality must be considered and also the mechanical or physical condition 

 of the soil, and the amount of water present. 



IMPROVEMENT BY TILLAGE. 



There is a constant tendency of the potash and phosphoric acid of 

 soils to form compounds wholly insoluble or very difficultly soluble in 

 water. Unless they can be dissolved by water they are of no avail as 

 plant food. They are dissolved by acids of the soil and by secretions 

 from the root hairs of the plant. The finer the soils are in texture the 

 greater the surface they present to the action of these dissolving agents, 

 and consequently the greater will be the amount of material dissolved. 

 Thorough tillage breaks up the soil granules that are apt to be formed by 

 the surface tension of water and so facilitates the solution of these two 

 elements of plant food. It also helps to make nitrogen available by pro- 

 m.oting the process of nitrification. Extensive co-operative experiments 

 carried on by Cornell Experiment Station and the farmers of New York 

 State have shown that the yield of potatoes can be increased by from 

 twenty-five to fifty bushels to the acre by cultivating three or four times 

 more during the season than is ordinarily done. Evidently plant food was 

 liberated by the tillage, and this suggests a method of finding out whether 

 the elements potassium and phosphorous are deficient in the soil or 

 simply locked up in some insoluble compound where they are unavailable. 

 We might often liberate these elements by tillage at a greater profit than 

 supplying them by purchasing commercial fertilizers. 



TILLAGE TO REGULATE MOISTURE. 



Every farmer knows that his losses due to unreasonable water supply 

 are far greater than those due to lack of fertility. Without water, plant 

 food is unavailable no matter what the quantity or quality. Few of us 

 realize the enormous quantities of water used by plants. The results of a 

 few experiments along this line will help us to better understand the ques- 

 tion of soil moisture. It has been shown that farm crops use an average 

 of 325 tons of water for every ton of dry matter produced. Corn is some- 

 what below the average, so we will take it at 300 tons of water per ton 

 of dry matter. A yield of 50 to 60 bushels of corn per acre would produce 

 about four tons of dry matter. This would require 1200 tons of water, 

 which is equivalent to 10.6 inches of rainfall. Experiments have shown 



