8 THE WEED FACTOR IN THE CtTLTlVATIOX OF CORN. 



broad national way the subject of the relation of weeds to the cul- 

 tivation of corn. Consequently, in the year 1906 a circular letter 

 was sent to the different agricultural experiment stations in the 

 United States giving a general summary of the results already 

 secured and inviting them to cooperate in carrying on simultaneously, 

 through a wide range of soils and climatic conditions, an experiment 

 as outlined to test the relative merits of the mere removal of weeds 

 as compared with supposedly ideal cultivation. A list of graduates 

 of agricultural colleges who are engaged in farming in the various 

 States, together with a number of reliable farmers not coming under 

 that classification, was compiled, and these men were also invited 

 to cooperate with the Department of Agriculture in carrying on the 

 test. The results of these experiments are given in the following 

 pages. 



In the tables presented in this bulletin the yields of the unculti- 

 vated but weeded plats are expressed in percentages of the cultivated 

 plats, both for fodder and for grain. In the precipitation columns 

 of the tables are given, first, the actual rainfall for a 12-month period, 

 including the last three months of the previous year and the first nine 

 months of the current year, then the mean annual rainfall, and finally 

 the percentage of the actual rainfall expressed in terms of the mean. 

 The records of the weather station nearest to each point where the 

 experiments were conducted or of the station where conditions are 

 most comparable were taken. The columns containing the remarks 

 on soils and climatic conditions give the observations of each of the 

 cooperators covering these points. The headings of the other col- 

 umns of the tables are self-explanatory. 



METHOD OF CONDUCTING THE EXPERIMENTS. 



The early tests of five agricultural experiment stations covering 

 the relation of weeds to the tillage requirements of corn were all con- 

 ducted as a part of a series of experiments on the depth of cultivation. 

 All of them had plats of deep and shallow cultivation, and some had 

 medium-tilled, lt standard' '-tilled, and mulched plats. The non- 

 tilled plats were referred to as having been ''hoed" or ''scraped" in 

 all the experiments except those in Utah, where they were "scarified" 

 with a scuffle hoe. 



In the work conducted by the Department of Agriculture, beginning 

 in 1906, an outline was furnished each cooperator describing in detail 

 how the test should be made. The salient points in the outline were 

 as follows : A piece of land of very even productivity was to be selected ; 

 preparation for planting was to be made by thorough breaking and 

 harrowing and the planting was to be done by drilling on level land — 

 that is, without ridges. 



