160 ALFALFA FARMING IN AMERICA. 
somewhat greater danger of souring land when 
green crops are turned under than when they are 
left to ripen and decay somewhat on the surface be- 
fore being turned under. It is not easy to account 
for this fact. It is always well when turning under 
cover crops where alfalfa is to be sown to use a 
larger application of lime than one otherwise would 
use, since thus he avoids the danger of souring the 
land. 
Cowpeas however, may do soils good and may pos- 
sibly do them harm. It has been taught that cow- 
peas always build soil, whether the vines are taken 
away or left on the soil to be turned under. Prof. 
C. A. Mooers of the Tennessee Station has shown 
that cowpeas when cut and removed from the soil 
have a marked effect in depleting it of fertility. 
Probably they rob it rapidly of available phos- 
phorus. It is plain that when cowpeas are grown 
to prepare the land for alfalfa seeding they ought to 
be turned under, not taken away from the land. 
“Cut them and put the manure back?’’ Yes, but 
would it come back? 
The Soy Bean.—An easier crop to grow than the 
cowpea is the soy bean, and it also is a soil enricher 
and affords much humus when turned under. Soy 
beans are of many sorts. The large growing kinds, 
like the Mammoth Yellow, make the most vegetation 
for turning under, while smaller growing sorts make 
most seed in northern latitudes. Soy beans to do 
well need soil inoculation. It will come of itself if 
they are continuously grown on the same land. Soy 
