170 A PRACTICAL TREATISE 



has hee\i shown, by many curious experiments, that the air 

 and water are the chief sources of vegetation; and it is a 

 fact, that poor land, without manure, wiiich by the fortuitous 

 chances of the weather has produced tolerable green crops, 

 has been found more fertile after their production than before. 



When ploughed into the land, they however often remain 

 for several months before they decay, for their decomposition 

 goes on slowly beneath the soil, and they are therefore fre- 

 quently more beneficial to the second than to the first crop. 

 To turn them in effectually, they should be first heavily 

 rolled, and then followed by a trench plough, for the operation 

 cannot be completely performed with a common plough; and, 

 if not entirely buried, their points stick out between the fur- 

 rows, by which they are partly prevented from fermenting, 

 and a portion of their value as manure is thereby lost. 



The time of the year when they should be ploughed in, 

 must, of course, depend upon the nature of the crop, which 

 should always be buried before it arrives at perfect maturity, 

 or otherwise it will rob the land of that nutriment with which 

 it is intended to supply it. Most farmers take the first growth 

 of tares and clover, which, if fed ofl' early, is an economical 

 plan; but if mowed, it is only doing the business by halves, for 

 the land is thereby not only deprived of the dung of the cattle, 

 but the operation is then too long delayed, for the work should 

 be done in the heat of the summer, or, at the latest, early in 

 the autumn, while the sun lias the power to forward the fer- 

 mentation. The effect, indeed, will greatly depend upon the 

 season, for the process of fermentation is only slight when 

 checked by the want of free communication v>-ith the air; and 

 if the weather be cold, the power of the manure will be in a 

 great measure lost; but if the season be moderately moist, and 

 very warm, the fermentation will be much promoted, and the 

 crop will be converted, by putrefaction, into a mass of nutritive 

 mucilage. Nothing short, however, of an abundant crop will 

 liave that immediate effect, as a large mass decomposes much 

 more speedily than a small one; and, if very scanty, the latter 

 perhaps may not putrefy at all, or its decomposition will be so 

 very gradual that the land will be very little perceptibly the 

 better; but if such a quantity be turned under the earth as will 

 excite the force of fermentation, there can be no doubt but that 

 it will then be greatly as well as promptly benefited. Sir 

 Humphry Davy, indeed, says, "that this gradual decomposition 

 affords a supply of vegetable mould for several years;" but 



