EFFECT OF ORGAXIC REMAINS IX THE SOIL. 89 



never thrive well, even though the supply of nutritive 

 substances be ample ; and in tliese circumstances, the 

 beneficial influence of green manure and fresh stable 

 dung is unmistakeable. The mechanical condition of the 

 soil is, in fact, altered in a remarkable way by the 

 ploughing in of plants and their remains. A stiff soil 

 loses thereby its cohesion, becoming more friable and 

 crumbling, than it would be by the most diligent plough- 

 ing. In a sandy soil, on the other hand, a certain cohesion 

 is hereby produced. Every stem and leaf of the green- 

 manure plants ploughed in, opens up, by its decay, a 

 road by which the dehcate roots of the cereals may 

 ramify in all directions to seek their food. Here, too, 

 we must always remember, that the effect calculated to 

 be produced is a question of degree. Li many fields, the 

 roots left in the soil of a fine crop of green forage plants 

 vnll suffice to improve a succeeding cereal crop ; and a 

 field from which a crop of lupines has been taken, may 

 possibly give as fine a succeeding cereal crop as a 

 field of equal extent in which the lupines have been 

 ploughed in. 



All these observations tend to show the great import- 

 ance of the mechanical conditions which impart fertility 

 to a soil not originally deficient in the means of nourish 

 ing plants ; and that a comparatively poorer but well- 

 tilled soil, if its physical condition is more favourable for 

 the activity and developement of the roots, may yield a 

 better harvest than richer land. In like manner, it often 

 happens that the cultivation of a bulbous plant renders 

 the ground better suited for a following cereal, and that 

 a winter crop succeeding a green forage plant, turns out 

 aU the better, the richer the previous green forage crop 

 has been, or rather the roots left by it. 



Clover and turnips act favourably upon a succeeding 



