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The effects of competition on yield of grain was studied in mixed populations of a winter and a spring wheat (Triticum aestivum L.) cultivar sown in their respective planting seasons. Viable and nonviable seeds of the two cultivars, winter ‘Genesee’ and spring ‘Justin’, were mixed in 26 planting ratios. Separate nurseries were sown for the fall and spring planting seasons, respectively. The nature of the cultivars was such that only Genesee was harvested in the fall-sown experiment and only Justin in the spring-sown experiment, that is, fall-sown Justin winterkilled and spring-sown Genesee remained in the vegetative stage. In the fall-sown nurseries there was root or underground competition and a low level of aerial competition throughout the season. The results showed that winter wheat yields depended largely upon the density and vigor of the post-winter population stand. The Genesee plants showed excellent ability through tillering and vigor to compensate for stand differences. The yields of spring wheat were depressed by the presence of winter plants in their midst and this effect was approximately in proportion to the planting ratios. Conclusions from the study point towards the importance of breeding winter wheats with superior post-winter plant establishment.
Key Words: Population • Plant density • Cereals • Winter-hardiness • Stand or yield compensation • Spring establishment • Tillering • Planting rations • Seeding competition • Root competition • Triticum
2 Liberty Hyde Bailey Professor of Plant Breeding, Cornell Univ., Ithaca, NY 14853.
Received for publication March 31, 1978.
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