34 
BULLETIN 157, U. S. DEPARTMENT OF AGRICULTURE. 
though the yields of the past five years indicate that it is not. An 
effort was made in 1913 to determine the exact extent of the injury 
to the plants by harrowing with a spike-toothed harrow, the teeth of 
which were set almost perpendicularly. At this time there wa*s a 
heavy crust on the ground, which the plants were penetrating with 
difficulty. 
On May 21, when the plants were from 3 to 4 inches high, four 
areas were staked off on plat 22D, and the plants in each area were 
counted before the plat was harrowed. Each area was 3.3 feet 
square, thus containing 475W °f an acre, so that the total area of the 
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Fig. 17.— Graphs showing the average percentage of moisture in the first 6 feet of soil at the beg innin g, 
in the middle, and at the end of the crop season, as found in the spring-cultivation tests of winter 
wheat at the Nephi substation, 1909 to 1913, inclusive. 
four units equaled 10 1 00 of an acre. About one week after harrowing, 
the plants in each area were counted again and the loss due to har- 
rowing was determined. On the basis of the figures obtained, the 
stand was 218,000 plants per acre before and 193,000 plants per acre 
after harrowing, a loss of 25,000 plants, or 11.54 per cent. This loss 
alone would allow the plants greater freedom for development, and it 
might be expected to increase the number of culms per plant. 
To determine the effect of harrowing on the production of culms 
the total number per unit area was determined just before harvest 
and the average number of culms per plant calculated. The average 
