ORGANIC MATTER AND NITROGEN 



323 



Organic matter has a wonderful effect in loosening heavy soils. 

 Improvement in this direction can best be accomplished by growing 

 grass and by pas- 

 turing. Combin- 

 ing red-top, timo- 

 thy and clover 

 makes an excellent 

 grass mixture for 

 any heavy soil. 

 The roots of 

 grasses loosen the 

 soil and in a large 

 measure prevent 

 puddling. 



The growing 

 of sweet clover on 

 clays for soil im- 

 provement is 

 highly recom- 

 mended. The 

 deep roots pene- 

 trating the "tight" 

 subsoil improve 

 drainage, favor 

 aeration and add 

 much organic 

 matter (Fig. 214). 



The use of air- 

 slaked lime or 

 quicklime on clays 

 tends to develop 

 better tilth, espe- 

 cially when acid. 

 This effect, how^ 

 ever, is percepti- 

 ble only when 

 lime is used con- 

 tinuously for 

 several years. Usually clays are not acid or only slightly so. 



Organic Matter and Nitrogen. Clay soils are commonly 

 deficient in organic matter and nitrogen, especially those which 



Fio. 214. The upper portion of a sweet clover root, 

 roots will puncture tight and hard subsoils. 



Such 



