PE RRS, Se ag ME ey ee ae en fe ee SORCERY ON Pe eT 
7 y * be + ot AN 's the 
392 MINNESOTA STATE HORTICULTURAL SOCIETY. 
Now, most farmers in the state who have tried subsoil plowing 
know that the subsoil is not loose. Although the surface may be so 
loose as to blow badly,yet it is remarkable how firmly compacted the 
subsoil is at a depth of sixteen inches. 
A mechanical soil analysis of the Experiment Station farm soil 
lends much aid in explaining the beneficial results obtained from 
subsoiling the land from which the sample was taken. * * * 
It will be noticed that there is very little sand in this soil,and a 
very large amount of silt. These silt particles are nearly as fine as 
clay,and it is well known that soils composed largely of silt pack very 
firmly, as does clay. In fact, these two kinds of soil resemble each 
other quite closely,inasmuch as they are both generally well supplied 
with the elements of plant food, but both difficult to work if plowed 
when wet. This firmly packed condition of the subsoil has acted in 
two ways to deter the growth of the crops grown thereon. It has 
prevented the rain water from soaking in quickly, so that water de- 
posited by summer rains was largely vaporized before it permeated 
the subsoil, and its poor absorbing power prevented its holding 
large quantities of water even when these were supplied. The fact 
that in this region large quantities of water fall in a very short time 
makes it imperative that not only the surface soil but also the sub- 
soil be in a condition to absorb it quickly and freely, for, if the 
surface alone be used as a reservoir, it is soon exhausted by reason 
of the rapid rate of evaporation. It has also served by excluding air 
and moisture to prevent the decomposition and nitrification which 
render the fertilizing materials in the soil available for the use of 
the growing plants. Thus, the plants have only received nour- 
ishment from the surface soil, while had the subsoil been loosened 
they would have had a much larger store to draw from. 
SUGGESTIONS. 
Subsoil plowing, although a means of conserving moisture, does 
not produce it, and is, therefore, not a substitute for irrigation where 
the rainfall is too small to produce crops. 
Where there is a hard,dry subsoil, subsoil plowing is to be recom- 
mended. 
Where the subsoil is loose, gravelly or sandy, subsoiling is proba- 
bly unnecessary or may even be injurious. 
Do not subsoil when the soil is very wet, either above or beneath, 
as there is great danger of puddling the soil,thus leaving it in worse 
condition than before. This is one of the reasons why it is better to 
subsoil in the fall than in the spring. 
Ifthe ground be subsoiled in the fall, the winter and spring rains 
have ample opportunity to soak in, that being the season of greatest 
rainfall and least evaporation. 
Subsoiling in the spring may be a positive detriment if the 
subsoil be extremely dry, as in that case the rain water is partially 
removed from the young plant by the absorption of the bottom 
soil. Ifthe spring rains were heavy, this would not be a disadvan- 
tage. 
The effects of subsoiling land having a “gumbo” subsoil has not 
been ascertained, but, if done at the proper time, it would doubtless 
