SOIL FERTILITY DEFINED 79 



sunlight by too thick growth of grain. Clover and alfalfa seedings 

 are generally more successful when the nurse crops are not sown 

 too heavily. A less amount of grain sown per acre enables the 

 young seeding to get more sunlight. When nurse crops are drilled 

 in a north and south direction, much more of the midday sunlight 

 reaches the young clover or alfalfa, thus insuring a better stand 

 of the hay crops than when the nurse crops are drilled east 

 and west, or sown broadcast. This is especially true in the 

 northern states. 



Protection From Injxory. — ^A farmer may be defeated in his 

 plans for raising good crops if he fails to protect them, if need be, 

 from injury by animals, birds, flood-water, weeds; from injury by 

 insects, as beetles, worms and aphids which feed on the foliage; 

 from damage through lodging (smothering the seeding) ; and injury 

 by diseases as smut, scab, blight, and if possible, by certain rusts. 

 Proper fencing may be an important consideration in protection, 

 likewise poison bait for rodents and grasshoppers, spraying, 

 treating grain and onion seeds for smuts and seed potatoes for 

 scab, killing weeds by cultivation, getting rid of surplus water 

 by proper drainage, etc. 



SOIL FERTILITY 



Productive soils are commonly described as '^ fertile," also pro- 

 ductivity of such soils is most commonly referred to as ''fertility." 



Before proceeding further it is important to have a clear idea 

 of the meaning of fertiUty. In the first place the word "fertility" 

 is but the noun form of the adjective ''fertile," and hence carries 

 the same general meaning. 



Soil Fertility Defined. — ^Fertility means '^ state or quality of 

 being fertile; fruitfulness; productiveness." Soil fertility^, there- 

 fore, is to be interpreted to mean the power of a soil to produce 

 good or large yields. 



To maintain soil fertility nleans to maintain productivity. 



To increase fertility means to increase the productive power of 

 a soil, or to cause it to produce still better jdelds. 



A soil is said to have lost its fertility when it ceases to be pro- 

 ductive, or when it no longer possesses the ability for producing 

 good yields (Fig. 29). 



Fertility does not mean the ability of a soil for producing the 



1 E. J. Russell, Soil Conditions and Plant Growth. 



