434 
WISCONSIN STATE AGRICULTURAL SOCIETY. 
theoretically^ if the normal yield of a soil is fifteen bushels per 
acre, if we plow under a year’s growth of clover, we ought to get 
thirty bushels, because we have two years’ supply of plant food in 
the soil. There is a principle, however, which interferes with this 
result. The soil is very conservative. It is not easy to get out of 
it all we put into it. A dressing of farm yard manure or a crop of 
clover plowed under, is not by any means taken up by the growing 
plants in a single season. In heavy soils especially, decomposition 
proceeds very slowly, and it may be several years before all the 
plant food supplied by a crop of clover is given up to the plants. 
.Still the fact remains that when we plow under a year’s growth of 
clover, we have accumulated in the soil an extra quantity of plant 
food, equal to the annual supply rendered available by the pro¬ 
cesses of agriculture and the decomposing and disintegrating action 
of sun and air, heat and cold. And it is this fact that lies at the 
basis of all judicious rotations of crops. I cannot but feei that we 
are on the eve of many important discoveries which will enable us 
to add greatly to the yield of our crops and the profits of our 
farming. 
We have learned how to make a sheep produce as much mutton 
from one year’s feed, as was obtained from three or four years’ feed 
less than a century ago. We shall learn how to get out of our farm¬ 
yard manure all, or nearly all, its valuable plant-food in a single 
year, if we so wish, and consequently be able to raise a much larger 
crop. We shall have the matter more under control. 
We plow under a crop of clover for wheat, and in this way get 
two years’ supply of plant-food for the wheat. We ought to double 
our crop of wheat. We ought to get as much wheat from the one 
crop every other year as from two crops of wheat grown succes¬ 
sively on the same land. The advantage of the plan, as I have said, 
is in saving the seed for one crop and the labor of putting in the 
crop and cutting it. 
But I feel sure that growing a crop and plowing it under, merely 
to enrich another crop, is not always the most economical plan. It 
is good as far as it goes. It is far better than growing grain crops 
year after year on the same land. 
But there is a better wav. There is much nutriment in the do- 
V 
ver, and this nutriment can be taken from the clover and still leave 
nearly all the elements of plant food in the excrements of the ani- 
