1198 
Journal of Agricultural Research 
Vol. XXXI, No. 12 
If irrigation such as that maintained by Hall caused a decrease in 
nitrate nitrogen formation, it is quite certain that excessive irrigation 
would cause a greater decrease. Spring rains also reduce the quan¬ 
tity of nitrate nitrogen in the soil. It is quite possible that an in¬ 
crease in moisture, either by natural causes or by irrigation, decreases 
the protein content of wheat indirectly through its reduction of the 
nitrates in the soil. 
The difference in the yields obtained from continually cropped 
and summer-fallowed plots corresponds very closely to that obtained 
by farmers on the dry land in the same locality. Even in the irrigated 
sections of Gallatin Valley the farmers find a wide difference in the 
yields of grain when grown continuously or when grown on summer- 
fallowed land. Nor can the difference in the grain yields obtained by 
farmers on irrigated land by these two methods of cropping be 
attributed to a difference in moisture conditions of the soil. The 
farmers of the irrigated districts abandoned the general custom of 
alternate fallow and crop several years ago and adopted a system of 
rotation with clover or some other legume as one of the crops. This 
practice has kept up the organic content of the soil and also the yields 
of grain, in marked contrast to the results obtained in former years 
when some farmers attempted to grow grain continuously. 
CONCLUSIONS 
Plots alternated with fallow and crop produce more spring and 
winter wheat per acre than plots of the same soil type cropped con¬ 
tinuously. 
Plots alternated with fallow and crop contained on an average 
more moisture to a depth of 3 feet than the plots cropped continu¬ 
ously. The greatest difference in moisture content occurred with 
spring wheat when the plants were making their most rapid growth. 
With winter wheat the greatest difference in moisture content 
occurred at a time when the soil was well supplied with moisture 
and before the plants were making their most rapid growth. 
Plots alternated with fallow ana crop contain more nitrate nitrogen 
"during the cropped year than those cropped continuously. This 
extra supply of available nitrogen undoubtedly accounts for the alter¬ 
nate fallow and cropped plots producing straw and grain of a higher 
nitrogen content than those cropped continuously. 
Nitrate nitrogen in the alternate fallow and crop plots shows a 
greater decrease in parts per million in the cropped years than does 
the continuously cropped plots. This decrease started before the 
wheat plants were large enough to take up much plant food from the 
soil and must be explained largely on the theory of leaching. A 
continuation of the decrease may be explained on the supposition 
that the wheat plants were taking nitrates from the soil faster than 
they were formed. 
The higher yields and protein content of wheat grown on the alter¬ 
nate fallow and crop plots over those on plots cropped continuously 
can not be explained from the standpoint of moisture. The fact 
that the fallow plots always produced larger yields and grain of a 
higher protein content than the plots cropped continuously indicates 
that nitrate nitrogen is certainly a factor, and probably the greatest 
factor, in controlling yields and quality of wheat in Montana. 
