312 TWENTY-FIFTH ANNIVERSARY REPORT. 
season, designed for the purpose of allowing the plants either to fall 
upon the ground when they are killed by the winter, or, if they 
survive the winter, to be turned under the following spring with 
the intention of thus creating a continual supply of humus. 
“Another advantage to be gained by the use of cover crops is that 
some kinds of plants may be used for this purpose by which the. 
amount of nitrogen compounds in the soil may be increased.” 
In the Fifteenth Annual Report!” of this Station the results are 
given of a series of trials of several crops for this purpose. The 
' crops were as follows: Mixtures of Canada peas and buckwheat, 
blue peas and buckwheat, cowpeas and buckwheat, or winter vetch 
and winter rye, and sweet clover, mammoth clover, sainfoin and 
dwarf Essex rape. Since the object of the cover crop is to add 
humus to the soil, and since the humus is produced by the decay of 
the plant itself, then it is evident that the most satisfactory cover 
crop, other things being equal, is the one which makes the greatest 
erowth, that is, produces the most humus. It follows necessarily 
from this that the best cover crop in one neighborhood might not be 
the best in another owing to the plants comprising. the cover crop 
being better adapted to the one section than to the other. There are 
some other points also that have to be considered. There are cer- 
tain plants which make a good growth but are barred out of use as 
cover crops owing to their tendency to become weeds. Sweet clover 
(Melilotus alba) is, in some neighborhoods, in this class. Others, 
like rye, are sometimes avoided because they form such a dense 
sod as to render the orchard very difficult of cultivation. 
The mixture of Canada peas and buckwheat was found to be 
very satisfactory, the only possible objection being that the exceed- 
ingly rank growth, averaging nearly two and a half feet in the 
latter part of September, interfered rather seriously with the gath- 
ering of the fruit. This was found particularly obectionable on wet 
days. The plat planted to this crop had been previously planted 
to crimson clover which had failed. 
The plat of blue peas and buckwheat, while not standing quite 
so thick upon the ground, made fully as good a growth. It is sus- 
pected, however, that it is somewhat more difficult to get a stand 
with the blue peas than with the Canada peas. 
The mixture of cowpeas and buckwheat looked quite ell 
chiefly, however, from the appearance given by the buckwheat since 
7 Rpt. 15:440 (1806). 
