At the request of the Director three samples were taken from the Russian Thistle plat on as many different dates, two weeks apart, and submitted to chemical analysis. The samples were taken by cutting within half an inch of the ground; the “heights” reported below are from measurement of the samples after cutting.
Patrick, G. E.
"Report of the Chemist.,"
Bulletin: Vol. 3
, Article 5.
Available at: https://lib.dr.iastate.edu/bulletin/vol3/iss26/5