Secondary roots are generally initiated approximately 2 cm below the soil surface regardless of whether the seeds are sown at that depth or deeper. In one experiment, conducted in the greenhouse in January, the seedlings established secondary roots between 1 and 2 cm below the soil surface, even when the seeds were planted 7.5 cm deep. In an identically conducted experiment in April, the zone of secondary root initiation was directly related to depth of planting with some being as deep as 4.6 cm. The environmental factors which were variable between the 2 experiments were photoperiod and temperature. All 5 oat varieties produced the same root depth patterns.
Proceedings of the Iowa Academy of Science
©1961 Iowa Academy of Science, Inc.
Rodgers, P. L.
"The Effect of Variety and Depth of Sowing on Depth of Secondary Root Zone in Oats,"
Proceedings of the Iowa Academy of Science, 68(1), 124-128.
Available at: https://scholarworks.uni.edu/pias/vol68/iss1/19