carried off from the surface by every faintest breeze and weakest sun ray. To prevent 

 this, the maintenance of a soil mulch on such surfaces as are exposed to the moving air 

 or direct sunshine is a necessary precaution. A soil mulch may be made by means of 

 a light harrow. Sometimes, too, it may be made by a roller. The roller has usually 

 just the opposite effect; under certain conditions, however, it is of value in this con- 

 nection. To illustrate, it often happens that two or three weeks after seeding, before 

 the grain is up high enough to protect the soil surface from winds and sunlight, a crust 

 forms and moisture evaporation goes on apace. Going over such a field with a light 

 roller breaks the crust and forms a soil mulch which effectually stops the loss. 



Humus Conserves Moisture 



Humus absorbs and retains moisture much more readily than any other constituent 

 of the soil. Hence one of the best methods of improving the moisture storing and mois- 

 ture conserving powers of a soil is to increase its humus content. This may be done 

 by the frequent turning under of sod and by the use of barnyard manure. 



(2) WARMTH 



For plants to grow rapidly, warmth as well as moisture is an absolutely necessary 

 condition. 



Drainage Warms Soils 



Drainage was shown to be probably the most important factor in making for 

 moisture conservation. Drainage as an influence affecting soil temperature is of even 

 greater importance. Undrained soils are always cool, usually too cold to favour plant 

 growth, save in the case of certain species accustomed to such peculiar conditions. 

 Practically all cultivated plants require warm soils. Drainage will warm the soil by 

 carrying off surplus moisture and enabling air to enter. 



Soil Mulch Affects Soil Temperature 



Once a crust has formed on the surface of the soil, water escapes rapidly through 

 the pores, evaporating as it passes off. The change from liquid to gaseous form means 

 the absorption of large quantities of heat by the escaping water, and in this way much 

 heat is taken out of the soil. Thus in spring, when heat is of such paramount importance 

 it not infrequently happens that a field lying under a bright sun is going down in tem- 

 perature rather than rising, for the reason that much moisture is escaping from the 

 surface by evaporation. To prevent this and stop the cooling-off process, all that is 

 necessary is a cut with a common harrow, that is, a mulch should be formed. 



Humus Warms the Soil 



After drainage and the soil mulch, the colour of the soil is an important factor 

 affecting soil temperature. Dark soils absorb heat readily and rapidly. Humus has 

 the effect of darkening soils, hence the increasing of the humus content of a soil is an 

 important and practical method of raising the temperature of a soil that due to its 

 colour might otherwise be slow in warming up. 



(3) PLANT FOOD 



The supply of plant food in a soil is very commonly supposed to be the measure of 

 its crop producing powers. Such, however, is not exactly the case. Even the most 

 barren soils, so far as plant food is concerned, may in a few years be made to produce 

 most excellent crops provided the other conditions of plant growth be right. Any 

 soil to which humus can be added at not too great expense will shortly be found to 

 yield profitable crop returns. 



Commercial fertilizers might be of some value in building up a worn-out or barren 

 soil, in as much as they will supply more or less immediately available plant food, 

 and in the case of certain fertilizers being used, such as land plaster, lime or ashes, will 



