UNITED STATES DEPARTMENT OF AGRICULTURE 
In Cooperation with the 
Montana Agricultural Experiment Station 
DEPARTMENT BULLETIN No. 1310 
Washington, D. C. 
January 16, 1925 
EXPERIMENTS WITH FALLOW IN NORTH-CENTRAL MONTANA 
By George W. Morgan, Associate Agronomist, Office of Dry-Land Agriculture 
Investigations, Bureau of Plant Industry 
CONTENTS 
Page 
Introduction... 1 
Soil on which the experiments were made... 2 
Climatic data 2 
Experimental conditions 4 
Results with small grains on fallow, on disked 
corn ground, and with continuous cropping. 4 
Results with corn on fallow and with contin- 
uous cropping 7 
Page 
Results with fallow and green manures 8 
Results of plowing at different times for fal- 
low 9 
Results of plowing at different depths for fal- 
low 10 
Results of manuring fallow... 12 
Water stored during the fallow period 13 
Summary 14 
INTRODUCTION 
This bulletin presents the results of experiments with summer fal- 
low during the seven years from 1917 to 1923, inclusive, at the Assin- 
niboine Field Station, located 8 miles southwest of Havre, Mont. 
The results are printed as a report of progress rather than as giving 
final or definite conclusions. Throughout the period of the experi- 
ments, except possibly in 1923, climatic conditions were abnormally 
unfavorable to crops. A careful analysis of the climatic records for 
the 44-year period from 1880 to 1923, inclusive, shows that the last 
seven years are representative of the most unfavorable conditions to 
be expected rather than of the average. 
Land that lies over the season in a cultivated condition without 
being cropped is known as summer fallow, fallow, or summer tillage. 
It is confined largely to arid and semiarid regions and is seldom found 
in humid sections or on irrigated land. 
Summer fallow has been used more generally in the intermountain 
valleys and certain farming sections between the Rocky and the 
Sierra Nevada Mountains than it has on the Plains east of the Rocky 
Mountains. West of these mountains the precipitation falls mostly 
during the winter either as slow and continued rain or as snow. At 
this time evaporation is low, and a large percentage of the water is 
stored in the soil. In the Plains east of the mountains more than 70 
per cent of the precipitation comes during the growing season. It 
may come in the form of light and scattered showers, with the result 
that the water is largely lost by evaporation ; it may come in torrential 
rains with a heavy loss by run-off; or it may come in slow continued 
10210°— 25f 1 
