SUMMARY 
1. In determining the effect of competition between 
single-row test plats as a source of experimental error in 
crop yield tests, the relative yields of two crops planted in 
blocks containing several rows have been regarded as the 
true relative values for the crops tested. In ascertaining 
some of these true values, the outer rows of the plats have 
been discarded in order to eliminate almost entirely plat com- 
petition. Plats were sufficiently replicated to secure quite 
reliable relative yields for the conditions under which they 
were grown. 
In plat competition tests in 1913 with two rates of plant- 
ing Turkey Red wheat, the thin rate yielded 68 per cent as 
much as the thick rate when grown in single alternating 
rows, while in five-row blocks the thin rate yielded 90 per 
cent as much as the thick rate. Competition in rows with a 
thicker rate of planting caused the thin rate to yield rela- 
tively 24.4 per cent too low. In a similar test in 1914 the 
thin rate yielded relatively 56.8 per cent too low. 
2. In 1913, competition between alternating rows of two 
rates of planting with Kherson oats caused the thin rate to 
yield relatively 20 per cent too low. In 1914, similar single- 
row competition caused the thin rate to yield relatively 34.3 
per cent too low. 
3. In 1914, competition between alternating single-row 
plats of Turkey Red wheat sown at two rates reduced the 
relative number of stools per plant approximately 37 per cent 
for the thin rate. There was a similar reduction of 20 per 
cent for Kherson oats, due to plat competition. 
4. The relative competitive effect of varieties varies in 
different years, due to difference in adaptation to the seasonal 
conditions. 
In 1913, competition with Turkey Red winter wheat in 
single rows caused Big Frame winter wheat to yield rela- 
tively 10.3 per cent too high. In similar competition in 1914 
Big Frame yielded relatively 12.4 per cent too low. 
In 1913 there was practically no competitive effect be- 
tween alternating rows of Turkey Red and Nebraska No. 28 
winter wheat varieties. This was due to abnormal climatic 
conditions. However, in 1914 under rather normal condi- 
tions competition between single-row plats caused the Ne- 
braska No. 28 to yield relatively 25.9 per cent too low. 
