METHODS OF SUPPLYING ORGANIC MATTER. 55 



eluded from the air, it will remain almost unchanged 

 for years; but as soon as you bring it toward the 

 surface where the air can obtain access, decay com- 

 mences. 



There are then two ways in which this disappear- 

 ance of organic substances goes on in the soil: first, 

 as it is used for the food of plants; second, as it is 

 decomposed by being brought in contact with air. 



From what has now been stated, it is obviously for 

 the interest of the farmer to keep up the supply of 

 organic matter in his soil : an equivalent at least for 

 every thing taken off should, as far as possible, be 

 returned in the shape of manure; peat and composts 

 are good forms of adding large quantities. 



But the best way of all when the land is run down, 

 is to cultivate green crops for ploughing under; such 

 as clover, buckwheat, vetches, etc. etc. a. Though 

 plants draw much of their organic part from the soil, 

 yet the greater proportion comes from the air through 

 the leaves ; consequently when a crop of clover is 

 ploughed in, there is, in addition to what it has taken 

 from the soil, much more than half its weight which 

 came from the air, aod is therefore a clear gain to the 

 soil. In this way the organic matter may be La or eased, 

 and even the poorest land be gradually brought up to 

 a state of fertility, b. Every good farmer should 

 w r atch his fields carefully, and see that they do not 

 become deficient in this very important part. When- 

 ever or wherever we see land losing it from year to 

 year, it is certain that there is bad management some- 

 w r here. 



The farmer must not suppose that by this or any 

 other system he can bring up his worn out land in one 

 or two years : the progress of improvement will be 

 gradual. He must persevere in the use of green crops, 

 bringing them in frequently, and returning at the same 

 time in the si ape of manure as much as may be of the 



