CROPS. 463 



foot is taken, this may be a very inadequate representative of 

 other parts of the field. If the soil is taken from the surface, or 

 that part of the soil which is cultivated, yet there is the soil 

 under this, into which the roots of the plant may extend them 

 selves, and which may contain elements of which we are not 

 apprized. In the chemical analysis of a soil, it is known, like 

 wise, that much of the active portion, all the vegetable portion, 

 is dissipated by heat, and no account is obtained of it but by the 

 loss in weight. The analysis of a soil, likewise, though it may 

 give all its component parts, is sure to destroy their combination, 

 and disturb the relations which they held to each other. There 

 is another great omission in this case. Notwithstanding all the 

 analyses which have been given of soils and products, where the 

 amount of mineral elements removed has been most particularly 

 determined, yet I have met with no instance of the analysis of a 

 soil immediately after the removal of the crop ; by which, on 

 comparison with its condition at the time of sowing, the actual 

 loss could be detected. This is a great desideratum, which we 

 may hope will presently be supplied. 



A great many exact calculations have been made in reference 

 to the weight of straw compared with the weight of grain, and 

 the weight of stubble, when wheat is reaped with a sickle, com 

 pared with the whole weight of grain and straw. These results 

 must, in different cases, be so affected by the seasons and soil, 

 by the amount of crop, by the time which the plant has had to 

 mature itself in, by the height at which the grain is cut, and by 

 the condition of the straw when dry, that it would be difficult 

 to draw any practical rule from them. In ten different experi 

 ments made in reference to this point, which have been shown 

 me, no two agree. 



In respect to the manures proper for wheat, I shall say some 

 thing in another place. Every one seems to acknowledge the 

 value of potassium, the principle which is found in common wood 

 ashes. This accords with the result of my own experience and 

 observation ; for when called upon, in the way of my official 

 duty, to examine the modes of cultivation and manuring, in no 

 less than thirty-six hundred experiments in the culture of wheat, 

 I found that wherever ashes were used upon the field, their effi 

 cacy was emphatically commended. The chemical analysis of 

 wheat, taking straw and grain together, gives only a small pro- 



