SOIL CONSERVATION EASY 87 



lation of organic decay with its humic acids will also 

 have a good effect in rendering the potash available. 



The farmer on upland clay soils who practices a good 

 rotation and maintains and increases the humus-making 

 material in his soil, will seldom need to buy potash or 

 nitrogen if he limes his soil once in four or five years, for 

 the legumes will give him the nitrogen and the lime and 

 organic decay will help release the potash. 



A good fertile soil is one that has a considerable 

 proportion of organic, that is, vegetable and animal mat- 

 ter in it. The most of this is in a dead and disintegrated 

 condition, but some of it is in living forms that we call 

 bacteria. These minute living organisms exist in the 

 decaying particles and could not live in this soil without 

 them, and when they are not there the soil is called dead. 

 Heat and water, when excessive, will kill them, and this 

 sometimes occurs. They need both heat and moisture, 

 but only in moderate degrees. 



To maintain the needed bacteria there must be a con- 

 tinuous addition of decaying as well as living vegetable 

 matter for them to live and multiply upon. In other 

 words, there must be plenty of humus in the soil, for 

 humus is decaying organic matter. The nitrogen con- 

 tent of the soil is largely dependent upon and often exists 

 in proportion to the amount of humus there. And nitro- 

 gen we know to be one of the most needful elements upon 

 which all plants, whether large or small, feed. 



The legumes contain a larger proportion of nitrogen 

 than ordinary vegetation. There are some soiling crops 

 that may be considered as specially valuable. Buckwheat, 

 rye and the cowhorn turnip are of this character. They 

 will tame and benefit wild and barren soil and flourish 

 over a wide range of climate. The rye must be turned 

 under promptly in springtime before it drains the soil of 

 moisture. 



