BULLETIN 156. J [MARCH, 1907. 



Ontario Department of Agriculture. 



ONTARIO AGRICULTURAL COLLEGE. 



PRINCIPLES OF TILLAGE AND ROTATION. 



By Wm. H. Day, B.A., Lecturer in Physics. 



It is the chief purpose of tillage to improve the condition of the soil 

 in order that it may the better minister to the plant, which needs mois- 

 ture, air, warmth, food, and proper sanitary environment. 



Perhaps the most important factor in crop production is the proper 

 supply of moisture, for on this depend all the others. If the water is 

 excessive, the soil is cold, and germination and growth slow, air cannot 

 reach the roots, and the plant suffocates, grows sickly, and refuses to 

 assimilate the food. If, on the other hand, the water is insufficient, no 

 amount of air, warmth or food can avail to produce a crop. Hence we 

 shall notice first, tillage in relation to soil moisture. 



It may be well at this juncture to inquire, "Whence do crops draw 

 their supply of moisture? Do they draw it mainly from the rains that fall 

 throughout the growing season, or do they draw it rather from the store 

 of water in the soil beneath, accumulated there from the April showers, 

 the snows of winter, and the rains of autumn?" This is a vital point, 

 on it hangs the whole question of cultivation. If the supply is drawn 

 mainly from the summer rains, then our cultivation must be such that 

 the soil will absorb quickly the water of those summer rains, and rid 

 itself quickly of the surplus ; if it is drawn mainly from the spring, winter 

 and autumn precipitation, then our cultivation must be varied accord- 

 ingly. Whether they draw from the summer or winter precipitation, 

 depends to a certain extent upon the season. During a very wet season 

 plants feed largely upon current rains, but during a moderate or dry 

 season they have to draw from the store below, because the evaporation 

 from the soil and the transpiration by the plant exceed the amount of 

 rainfall while the plants are growing. Let me give you here the result 

 o! a little test we have made on this point. Last year was a rather dry 

 season. We sowed wheat, peas, barley, and oats in four-gallon crocks, 

 and set them outside where they received all the rain that fell during 

 their period of growth, but this was found insufficient, and the crocks 

 were watered at intervals as necessary. The results were as follows : — 



