Culture of wheat. 63 



the crop, they rely on scattering over the field what little ma- 

 nure they have saved from their barn-yard, and that often by 

 greatly lessening their spring crop which needs its nourishment. 

 This practice, as a general system of husbandry, has been 

 too much over rated. Mr. Davey, in his agricultural chemistry, 

 observes, that when weeds are buried in the soil, by their grad- 

 ual decomposition, they furnish a certain quantity of soluble 

 matter ; but it may be doubted whether there is as much use- 

 ful manure in the land at the end of a clean fallow, as at the 

 time the vegetables clothing the surface were first ploughed 

 in. Carbonic acid gas is formed during the whole time by the 

 action of the vegetable matter upon the oxygen of the air, and 

 the greater part of it is lost to the soil in which it was formed, 

 and dissipated in the atmosphere. The action of the sun upon 

 the surface of the soil tends to disengage the gasseous and 

 the volatile fluid matters that it contains. And heat increases 

 the rapidity of fermentation ; and by the summer fallow nour- 

 ishment is rapidly produced at a time when no vegetables are 

 present capable of absorbing it. 



He farther observes, that land, when it is not employed in 

 preparing food for animals, should be applied to the purposes 

 of preparing manure for plants ; and this is eflTected by means 

 of green crops in consequence of the absorption of carbona- 

 cious matter in the carbonic acid of the atmosphere. In a 

 summer fallow, a period is always lost in which vegetables 

 may be raised either as food for animals, or as nourishment 

 for the next crop ; and the texture of the soil is not so much 

 improved by its exposure as in winter, when the expansive . 

 powers of ice, the gradual dissolution of snows, and the alter- 

 nations from wet to dry, tend to pulverize it and to mix its dif- 

 ferent parts together. 



By the method of green dressing, above described, two 

 great advantages are obviously derived. One is the acquisi- 

 tion of a supply of manure which wUl be sufficient to insure a 

 good crop ; and which in some conditions the farmer could ■ 

 procure from no other source : — The other is that by plough- 

 ing it in the spring, as in the case of buckwheat, before grass 

 and other noxious weeds gain strength, their prolific tendency 

 is greatly retarded if not entirely destroyed. And it cannot be 

 kept too much in mind, that all weeds by being suffered to 

 grow, exhaust the soil. Any given quantity of grass or weeds, 

 growing with a crop of wheat, or any other which is cultivated, 

 lessens its product in proportion to the weight of the green 

 weeds with that of the growing crop. 



But to remedy the evil resulting from summer fallowing 

 r 2 



