The effects of ozone and nitrogen fertilizer on tall fescue, ladino clover, and a fescue–clover mixture. I. Growth, regrowth, and forage production

Abstract

The effects of chronic ozone (O₃) and (or) nitrogen fertilizer on growth, regrowth, and forage production of ladino clover (Trifolium repens L. cv. Tillman) and tall fescue (Festuca arundinaceae Schreb. cv. Kentucky 31) grown in pots separately and together in open-top chambers in the field were studied from April 27 to October 19, 1979. Mean 7 h per day (0930 to 1630 EDT) O₃ concentrations for this period were as follows: charcoal-filtered air chambers, 0.03 ppm; nonfiltered air chambers (NF-1), 0.05 ppm; nonfiltered air chambers with O₃ added for 7 h per day (NF-2), 0.08 ppm; and ambient air, 0.05 ppm. Ozone reduced regrowth (milligrams of dry weight per plant per week) and total forage production of clover and the fescue–clover mixture. The magnitude of the reductions of clover growth and forage production corresponded in general to the O₃ levels. Growth of fescue was not significantly modified by O₃ treatments. Nitrogen fertilization stimulated the growth of fescue but had little impact on the growth of clover. Nitrogen fertilization did not change the response of either species to O₃.