The Relations to Yield of Certain Plant Characters of Winter Wheat as Influenced by Different Tillage and Sequence Treatments 1

M years of experimental work in the Great Plains have demonstrated that tillage treatments and crop sequences materially affect yields of winter wheat, but the manner in which these yield differences are related to the development of the wheat plant has received very little attention. The study reported herein was made to obtain information as to these relations. Yield records in the crop rotation and tillage experiments at Woodward, Okla., had shown that differences in winter wheat yields could be expected from given differences in cultural treatment and crop sequence. It was definitely known, for example, that on continuously cropped wheat land, average yields were higher where cultivation for the succeeding crop was started shortly after hkrvest than where it was delayed until fall; that average yields were higher on corn ground and cowpea ground than on milo or kafir ground; and that average yields on fallowed land were higher than on land where a crop had been grown. Differences in the quantity of water available for the crop under the different treatments were known to be sufficient to account for most of these differences in yield; but how the plant populations or the individual plants were affected was not known. The purpose of the experiment described here was to obtain inforr0ation on this point. A study of sampling methods and of forecasting yields was not in mind when these investigations were undertaken, although some of the results appear to have an incidental relation thereto. MATERIALS AND METHODS