FARMERS' INSTITUTES. 353 



path of the root. Dietrich made a similai* investigation by powdering some 

 sandstone and basalt, washing away all soluble matter by distilled water and 

 placing in weighed quantities of the pulverized material, seeds of various kinds 

 and allowing these to grow for a time. All dust was excluded by a covering of 

 cotton batting. At the close of the experiment the soil was washed with 

 water containing one per cent of nitric acid. It was found that the plants em- 

 ployed, especially lupins, peas, vetches, spurry, and buckwheat, assisted in 

 decomposing and rendering soluble these soils. Not only did the plants take 

 up mineral matter from these powdered rocks, but the soil contained in addi- 

 tion a larger amount of soluble matters than was found in experiments where 

 no plants were made to grow. The cereal grains had the same effect, hui in less 

 degree. Thus a pea plant made from 10 to 40 times as much material soluble 

 as did a wheat plant in the same conditions.* 



Thus the roots of plants assist in masticating the soil, rendering its materials 

 soluble even beyond the wants of that plant ; but this power is most strongly 

 manifested by the leguminous plants, and only feebly by the cereals. So far 

 as the immediate effect is concerned, the material thus made soluble, which 

 would otherwise remain inert, is as good as so much added directly to the soil; 

 so that practically green manuring adds mineral matter to tlie soil as well as 

 organic matter, and thus restores more to the soil than it took from it, so far 

 as present productiveness is concerned. This shows the fallacy of the objection 

 so often urged against the practice of green manuring. 



One advantage secured by green manuring over the usual process of feeding 

 to stock and using the excrement as manure, is that we thereby secure a greater 

 amount of carbonaceous material in the soil. In feeding, a large amount of the 

 carbon is oxidized in the animal, and escapes as carbonic acid in the breath. In 

 green manuring, the whole of the plant material is saved in the soil, and we 

 thus rapidly accumulate humus in the soil. By the vegetable matter thus 

 secured in the soil the physical properties of the soil may be greatly improved ; 

 the heavy clays are made more open and friable, and light sands are made more 

 compact and tenacious, more retentive both of moisture and manural matter, 

 and thus any tendency to leaching is mitigated. If you will consider for a 

 moment the influence of laying down to grass for a few years a heavy clay, and 

 the condition of culture secured by breaking up the green sward, you will find 

 proof of my first assertion. The clay is much easier to cultivate while the influ- 

 ence of the sward remains. When sandy lands become too open and light by 

 frequent plowings, the farmer "lays it down to grass to compact the soil," but 

 this compacting is essentially an accumulating of vegetable matter by the green 

 sward. Do not suppose me to hold that green manuring is the only kind of 

 manuring to be recommended and practiced ; I only want to call your attention 

 to certain advantages of this process, without entering into discussion in regard 

 to other kinds. 



A farm differs from almost every other kind of property in its capacity for 

 perpetual production. A liorse or a cow lives but a few years, and the problem 

 for the farmer is how to produce the greatest profit from them for the short 

 period of their life. But a farm never dies, — or never should die. It is a pos- 

 session for all time, and should be farmed with reference to its perpetual pro- 

 ductiveness. The man who for immediate profit "skins his farm" by injudi- 

 cious cropping is as short-sighted as if he should skin his living cow for the 

 profit in the hide. 



*How crops feed, pp. 326-7. 



45 



