UTILITY OF FALLOW CROPS. 267 



''Buckwheat, dried in the sun, yields only 0.681 per cent, 

 of ashes, of which 0.09 parts are soluble salts" [Lichig) ; 

 hence, these plants with others, have been called fallow crops. 

 It will be perceived, that the alkalies which the oxygen and 

 carbonic acid of the air are eliminating from the soil, will be 

 increased in this case, because the roots of the crop will per- 

 mit these agents to act with greater power. 



The power of growing plants to decompose the rocks, and 

 to eliminate alkalies, has already been frequently referred to : 

 and as but a small quantity of alkali is removed by the fallow 

 crop, the amount in the soil is, upon the whole, increased. 



2. It is further evident, that the roots leave in the soil nearly 

 as much vegetable matter, as is carried away in the stalks and 

 grain. This deficiency is made up by the influence of grow- 

 ing plants upon the humus of the soil. There is little doubt, 

 but that decay proceeds much more rapidly when the soil is 

 tilled, than when it is not ; and the reason is, the galvanic 

 agency of the roots and the facility which they offer for the 

 introduction of air and water by loosening the soil, tend pow- 

 erfully to hasten the decay of humus, or to convert the vege- 

 table matters into vegetable food. The fermentation of the 

 sod will be more complete when it is turned in deep, and the 

 gaseous products will be retained by the superincumbent 

 earth ; hence we may draw an argument for deep ploughing, 

 and for letting the sod remain until it has completely passed 

 through the fermenting process. 



II. Turning in green crops. The turning in of green 

 crops, has long been a reputed source of rendering barren 

 soils fertile. It is well suited to any soil which requires either 

 to be rendered lighter, or to be filled with veoretable matter 

 and salts. Light sandy soils, such as pine-barrens and loams, 

 which have been exhausted by a long course of cropping 

 without manuring, are most benefited, while stiff clays are 

 rendered much warmer, and more friable. 



Processes. 1. Green crops may be sown for the purpose 



