178 ANNUAL REPORT OF THE Off. Doc. 



locked up in soils of this character. In the other case, what is needed 

 is the introduction of vegetable matter, which will make the soil 

 more compact, more retentive of moisture and plant food, and a 

 better medium for the development of those living agencies which 

 are so important a factor in promoting the absorption of the atmos- 

 pheric elements. 



The question that naturally arises here is, what are the natural 

 agencies that must be invoked in order to accomplish these benefi- 

 cent purposes? First, the atmosphere, llie sun and air, cold and 

 heat. The air circulating freely in soil causes chemical changCis, 

 oxidizes, helps to rot the compounds, setting free food elements that 

 were locked up in unusable compounds; the warmth carried by the 

 air assists in the process. These are largely chemical changes, 

 though resulting as well in j^hysical improvement, as is evidenced 

 by the breaking down of hard particles by alternate freezing and 

 thawing. 



Tn the second place, water is a natural agent, as it is a universal 

 solvent, and its iiecr juovemcnt in soils makes active the dormant 

 constituents, which, being carried in dilute solutions, presents them 

 to the plant in usable forms. 



Third, organisms, low orders of life, which, while unseen, exist in 

 all soils for good or evil, the good ones existing only in soils that 

 permit the free circulation of air and water, for, like the higher 

 orders of life, they must have air, a proper degree of temperature 

 and the right amount of moisture, in order to live and perform their 

 functions. They feed upon the constituents of the atmosphere and 

 soil, and by their life and activity not only break down the insoluble 

 compounds, but add to the constitueuts by absorbing nitrogen from 

 the air. Those that work evil exist in soils that do not freely permit 

 the free circulation of air and warmth, and are cold and wet and free 

 from organic matter, thus they absorb oxygen from usable nitro- 

 genous compounds, setting the nitrogen free, thereby reducing their 

 crop-producing power. These organisms are also affected by the 

 condition of the soil, whether acid, alkaline or neutral; the good 

 ones, especially those which possess the valuable characteristics 

 of absorbing nitrogen from the atmosphere, do net thrive or mul- 

 tiply rapidly in soils that are acid. 



Fourth, growing plants, which by their presence not only pre- 

 vent the losses of food from the soil, but by their growth and the 

 subsequent decay of roots and stubble change and add to their 

 chemical and physical properties. A soil that is left bare during 

 the fall and (\arly spring loses the food that has been made available 

 duriug the growing season; it remains unabsorbed, and is readily 

 washed out, while one left bare daring the hot, dry months is not 

 only deprived of the improvement due to the growth of plants, but 

 is apt to have its living forces destroyed by the high temperatures 

 which then usually prevail, and which penetrate deeply in the ab- 

 sence of the cooling shade of plants. 



It is evident, therefore, that if we are to benefit by natural agencies 

 they must be directed; conditions must be made favorable for their 

 activity. If the sun, air, water, living organisms and growing plants 

 are to perform their functions in making plant food availai)le in 

 our soils, or in adding to their stores of nitrogen, the farmer must 

 provide the opportunity by better and more frequent cultivation, 



