GREEN MANURES. 



GREEN MANURES. 



pidity of these processes. Hence, in addition 

 to the sugar, gum, and starch of the plant, we 

 lose a large portion of its other substances, by 

 turning it in green. The products of this rapid 

 fermentation have been but little studied. Happy 

 the farmer who never witnesses the process ! 

 He should never induce it, and may generally 

 prevent its extension when once begun. It is 

 a dead loss to him ; but in all the other cases 

 of putrefaction, the products are valuable." 



Will not the remark made above by Dr. D., 

 that the alcohol formed during the vinous fer- 

 mentation washes away or is converted into 

 vinegar, account for the fact of what some far- 

 mers complain of, as souring the soil in turning 

 in heavy crops of green clover? We have 

 heard some very successful farmers and wheat- 

 growers assert that their experience in turning 

 in the clover crop before it had reached matu- 

 rity, or while abounding in sap, had been so 

 unfavourable, that they had relinquished the 

 practice, and chose either to feed it off with 

 sheep, or let it decay on the ground. 



Still, no one can doubt but that excellent 

 effects are produced by turning in green crops, 

 particularly such as buckwheat, of which three 

 or four can be ploughed in in a year; thus 

 evidently giving more geine than where the 

 ripened product is turned under. The danger 

 of the practice appears to arise from ploughing 

 in the green crop in that condition, and under 

 such circumstances, that the vinous fermenta- 

 tion and acetous one are so rapid as to convert 

 the valuable products into vinegar, and thus 

 seriously injure the land; or when the destruc- 

 tive fermentation converts the plant into sub- 

 stances unfit for the food or nutrition of vege- 

 tables. (Cultivator.) 



During the growth of plants, substances con- 

 taining a large proportion of carbon are ex- 

 creted or thrown out by the roots, and absorbed 

 by the soil. These substances were either in 

 excess, or unfitted for the nutrition of the 

 growing plants. They constituted, therefore, 

 excrementitious matters, through which the 

 soil received again, with usury, the carbon 

 which it had first yielded to the young plants 

 as food, in the form of carbonic acid. 



"The soluble matter thus acquired," says 

 Liebig, "by the soil is still capable of decay 

 and putrefaction, and by undergoing these pro- 

 cesses furnishes renewed sources of nutrition 

 to another generation of plants; it becomes 

 humus. The cultivated soil is thus placed in a 

 situation exactly analogous to that of forests 

 and meadows ; for the leaves of trees which 

 fall in the forest in autumn, and the old roots 

 of grass in the meadow, are likewise converted 

 into humus by the same influence : a soil re- 

 ceives more carbon in this form than its de- 

 caying humus hadlost as carbonic acid. 



"Plants do not exhaust the carbon of a soil 

 in the normal or regular condition of their 

 growth ; on the contrary, they add to its quan- 

 tity. But if it is true that plants give back 

 more carbon to a soil than they take from it, it 

 is evident that their growth must depend upon 

 the reception of nourishment from the atmo- 

 sphere in the form of carbonic acid. 



"Humus does not nourish plants by being 

 taken up and assimilated in its unaltered state, 

 74 



but by presenting a slow and lasting source of 

 carbonic acid, which is absorbed by the roots, 

 and is the principal nutriment of young plants 

 at a time when, being destitute of leaves, they 

 are unable to extract food from the atmo- 

 sphere." 



The supply of humus usually effected by 

 turning under clover, rye, buckwheat, &c., is 

 accomplished, as Liebig informs us, with much 

 greater certainty when the fields are planted 

 with sainfoin or lucern, a plan now universally 

 adopted in Bingen and its vicinity, the Palati- 

 nate, and other parts of Germany, where the 

 fields, thus treated, receive manure only once 

 every nine years. In the first year after the land 

 has been manured, turnips are sown upon it; 

 in the next followingyears barley, with sainfoin 

 or lucern ; in the 7th year, potatoes ; in the 8th, 

 wheat; in the 9th, barley ; on the 10th year it is 

 again manured, and the same rotation ensues. 

 Sainfoin and lucern are remarkable for the 

 ramification of their roots and the strong de- 

 velopement of their leaves, as well as for re- 

 quiring but a comparatively small quantity of 

 inorganic matter. 



"An immediate consequence of the produc- 

 tion of the green principle of the leaves, and 

 of their remaining component parts, as well as 

 those of the stem, is," says Liebig, "the equally 

 abundant excretion of organic matters into the 

 soil from the roots. 



"The favourable influence which this exer- 

 cises on the land, by furnishing it with matter 

 capable of being converted into humus, lasts 

 for several years, but barren spots gradually 

 appear after the lapse of some time. Now it 

 is evident that, after from 6 to 7 years, the 

 ground must become so impregnated with ex- 

 crements that every fibre of the root will be 

 surrounded with them. As they remain for 

 some time in a soluble condition, the plants 

 must absorb part of them and suffer injurious 

 effects in consequence, because they are not 

 capable of assimilation. When such a field is 

 observed for several years, it is seen that the 

 barren spots are again covered with vegeta- 

 tion (the same plants being always supposed 

 to be grown), while new spots become bare 

 and apparently unfruitful, and so on alter- 

 nately. The causes which produce this alter- 

 nate barrenness and fertility in the different 

 parts of the land are evident. The excrements 

 upon the barren spots receiving no new addi- 

 tion, and being subjected to the influence of air 

 and moisture, they pass into putrefaction, and 

 their injurious influence ceases. The plants 

 now find those substances which formerly pre- 

 vented their growth removed, and in their 

 place meet with humus, that is, vegetable mat- 

 ter in the act of decay. 



" We can scarcely suppose a better means 

 of producing humus than by the growth of 

 plants, the leaves of which are food for ani- 

 mals ; for they prepare the soil for plants of 

 every other kind, but particularly for those to 

 which, as to rape and flax, the presence of 

 humus is the most essential condition of 

 growth. 



"The reasons why this interchange of crop 

 is so advantageous the principles which regu- 

 late this part of agriculture, are, therefore, the 



585 



