CORN GROWTH FOLLOWING COVER CROPS - INFLUENCE OF CEREAL CULTIVAR, CEREAL REMOVAL, AND NITROGEN RATE

Rye (Secale cereale L.) cover crops often delay development and reduce yield of corn (Zea mays L.). A 3-yr study (1982-1984) was conducted t o investigate the influence of four rye cultivars and one wheat (Triti cum aestivum L.) cultivar, rate of N application in the spring, and re moval of above-ground cereal phytomass on growth and development of co rn. Experiments were carried out at the Elora Research Station, Ontari o, in a split-plot design, with two N levels (145 and 220 kg ha-1) and five cereal cultivars as main plots, and cereal phytomass removal or retention as sub-plots. Cereal cultivars were planted in September aft er corn harvest and corn was planted in the spring. Corn leaf number a nd height were monitored during early corn development and whole-plant dry matter and moisture of corn were measured in September. The respo nse of corn dry matter accumulation to cereal cover crop cultivar, N r ate, and above-ground cereal phytomass varied among the 3 yr the study was conducted. Cereal phytomass was largest in 1983 and the impact of the cereal cover crop on corn growth and development was largest duri ng this year. In contrast, the impact of cereal cultivar on corn was n ot associated with phytomass production among the five cereal cultivar s. The effects of cereal cultivar cover crop on corn growth and develo pment were largest for the rye cultivar Kodiak and the wheat cultivar Gordon, but these cultivars ranked third and fifth, respectively, in a bove-ground phytomass production in the spring. Increased N applicatio n could partially overcome the reduction in corn growth and developmen t due to the cereal cultivars Kodiak and Gordon, but this was not the case for the other cereal cultivars. Removal of above-ground cereal ph ytomass before corn planting generally did not influence the delay in development and reduction in yield of the subsequent corn crop. In con clusion, the reduction in corn dry matter accumulation in response to cereal cover crops is a complex phenomenon, involving quantity of cere al residue, cereal cultivar and, occasionally, N application.