30 
Colorado Experiment Station 
Fig’. 22 — Plot II. June 1918 before covering with tar paper. Note cir- 
cular appearance of patch. 
gave a bank to work to and by “moving the trench’' across the 
patch all the soil was turned over and the roots and rootstocks 
removed. The time necessary to do this first grubbing was one 
hour and a quarter. The time required for grubbing will, of 
course, vary somewhat with the type and condition of the soil. 
The soil in this case was worked with comparative ease, although 
it was dry. The application of the worker will also cause a var- 
iation in time required for doing the work. 
On July 23 a few plants had come up around the edges from 
underground parts outside of the grubbed area, and also a few 
shoots were found in the grubbed part. The entire patch was 
regrubbed, (time 1-2 hour) and 12 shoots were found on the 
ground actually grubbed the first time, all coming from the sol- 
id ground below that which had been turned over at the first 
grubbing. 
During the 1919 season this plot was left untouched. A 
large stand of other weeds came up on the plot but not over 3 per 
cent, of the original milkweed stand appeared. 
Plot IV. Summer Fallow 1918 Followed by a Cultivated Crop in 1919. 
— During 1918 this plot was given the following treatment: 
Plowed June 15, with a double-disc plow to a depth of 3 or 4 
inches. 
