THE CAUSES OF LOW YIELDS 257 



the following year. The "stubbling in" of fields is 

 generally an undesirable practice but its chief justifi- 

 cation in the minds of many farmers lies in the fact that 

 there are times and conditions in some of our medium 

 dry areas when land is put out of condition by fall plow- 

 ing and, as a result, gives disappointing yields. 



For economic reasons man must plow when time per- 

 mits and this may not be the best time. Nevertheless, 

 the condition of the soil at different seasons of the year 

 and in different years should be an important consider- 

 ation, when planning the season's operations. 



207. Plowing Tinder Heavy Stubble or Coarse Manure. 

 These substances when plowed under add considerable 

 organic matter to the soil but they do not decay rapidly 

 in a dry climate and may therefore leave the soil so 

 loose that the upward movement of moisture and the 

 downward growth of plant roots is interfered with thus 

 sometimes resulting in a decreased yield of the first crop 

 after the application. This is "one of our difficult 

 problems. Continuous grain-growing dissipates organic 

 matter; and coarse organic matter unless well inter- 

 mixed with the soil and firmly packed down may injure 

 the condition of the soil. 



When organic matter is badly needed as on the lighter 

 types of soil and those that drift neither stubble nor 

 manure should ever be burned, but when either is plow- 

 ed under the land should be worked down to a firm 

 condition. Manure should never be applied thickly for 

 grain crops in the Prairie Provinces. Ten loads per 

 acre on a forty-acre field is much to be preferred over 

 twenty loads per acre on a twenty-acre field. 



208. Too Late Plowing of the Fallow. In tests con- 

 ducted at Saskatoon the vield of wheat decreased at the 



