4 MASS. EXPERIMENT STATION BULLETIN 356 



of inbred lines, the building units for all hybrids, have been developed from open- 

 pollinated varieties by successive years of inbreeding operations within the 

 different varieties. 



An excellent discussion of how inbred lines are produced and how hybrid crosses 

 are made will be found in the references cited below: 



The What and How of Hybrid Corn. U. S. D. A. Farmers' Bulletin 



No. 1744. 1935. 

 Hybrid Corn and Its Place in Michigan. Michigan State College 

 Extension Bulletin 195. 1939. 



The production of hybrid seed corn is an expensive operation because it re- 

 quires rather extensive facilities for carrying along foundation material and also 

 because it requires careful and expert manipulation of the stock material to 

 insure the reliability of the hybrid seed. As might be expected, good hybrid 

 seed corn is necessarily more expiensive than good seed of open-pollinated varieties, 

 but the extra cost is an insignificant item when the superior performance of well- 

 adapted hybrid varieties is taken into consideration. This is assuming, of course, 

 that conditions of soil fertility and soil moisture and other external factors are 

 favorable for normal plant growth. Whenever one or more factors such as soil 

 fertility or soil moisture limit the productivity of the corn plant, the increased 

 yields of hybrid varieties over open-pollinated varieties are likely to be small 

 and their use may not be economically justified. It must be strongly emphasized 

 concerning hybrid corn varieties that the succeeding year's supply of seed can- 

 not be selected from a field planted to a hybrid variety. A new supply of seed 

 must be obtained each year. Any attempt to select one's own seed will only 

 lead to disappointing results. 



Selecting a Corn Variety 



The selection of a corn variety depends upon the purpose for which corn is 

 being grown, whether for grain or silage, upon the local soil and climatic condi- 

 tions, and upon the personal preference of the grower. There are certain guiding 

 principles, however, which the Massachusetts grower can follow when choosing 

 a variety. 



In general, the later a variety matures, the greater will be its yield of stover 

 and to some extent its yield of grain. This is assuming that maturity is reached 

 before a killing frost. There are many other seasonal and cultural factors which 

 will affect the yields and the maturity of all varieties. Hot summers with ade- 

 quate rainfall will produce good yields and early maturity. Periods of drought 



Table 3. -Variation in Time of Maturity for Eight Corn 

 Varieties Grown at Amherst, 1935-1938 



Variety 



1935 



Davis Flint 8/24 



Cornell 11 8/27 



Min-hybrid 401 8/29 



Wisconsin 350 8/27 



Cornell 29-3 — 



West Branch Sweepstakes 9/8 



Ohio W17 — 



New Jersey No. 2 — 



Note: Varieties were planted on May 19-21 each year. 



