SOIL MANAGEMENT 9 



deep, since the operation of plowing tends to loosen the soil. 

 Plowing sandy soils when they are a little wet forces the smaller 

 particles into the larger spaces and thus increases the quantity 

 of water retained. The most effective means of increasing the 

 moisture capacity of sandy land, however, is by the application 

 of humus or well rotted organic matter and its thorough incor- 

 poration into the deeper layers of the surface soil. 



The addition of humus is most effective w^hen used in connec- 

 tion with deep plowing f ollow^ed by compacting implements such 

 as the roller, the effect of the humus more than compensating for 

 any disadvantages from deep plowing. 



In very fine textured soils, such as clay and in loams that are 

 puddled, the pores are so small in size, and sometimes also in 

 total volume, that the soil has a very low moisture holding 

 capacity. Great care must be exercised in the management of 

 such soils, since it is important that they should be kept in a 

 loose granular condition. The finer the soil the greater the 

 importance of putting it in a granular condition. In coarse 

 sandy soils the individual particles may rest close together and 

 yet the pore spaces be too large to be most effective. On the 

 other hand, if a clay soil is pulverized so that the individual 

 particles rest close together, the spaces are so small that they 

 retain too much moisture and thus cut off ventilation and lessen 

 the rate of formation of available plant food material. 



Practical hints on tilth and tillage. — Since good tilth is 

 dependent upon a proper degree of granulation it is desirable 

 to study some of the factors affecting granulation. 



1. Adequate drainage is the most fundamental of these. It 

 is impossible to keep a poorly drained soil in good tilth. Such 

 a soil is naturally inclined to puddle and compact, and Avhen dry 

 works up into a rough, lumpy condition. Continual wetness 

 breaks down the granular aggregates by dissolving the cement- 

 ing material, and permits the particles to settle together. The 

 first step toward improvement of soil that is too compact is 

 provision for good drainage by some means, preferably by tile 

 underdrains. 



Drainage quickl^^ removes excess water and permits a reason- 

 able amount of drying, which results in cutting and granulating 

 the soil by means of checks and cracks. Without any other treat- 

 ment, drainage wall loosen the soil and provide an improved cir- 

 culation of water and gases throughout the earth mass. In 

 proof of this is the observation of farmers that underdrains in 

 heavy soil gradually increase in efficiency over a period of years. 



