INFLUENCE OF LITTER ON HERBAGE PRODUCTION IN THE MIXED PRAIRIE

Litter (dead plant material) increases production in xeric environment s but the nature of this effect is uncertain. The purpose of this stud y was to determine the relationship between litter quantity and herbag e production over a 4-year period as well as to determine the effect o f repeated removal of litter on production. The study was made in a St ipa-Bouteloua-Agropyron faciation of the Mixed Prairie association, ne ar Lethbridge, Alberta, Canada. Litter quantity was altered by mechani cal removal before spring growth and the residue separated into coarse and fine components. In Experiment 1, the effect of litter on herbage production was tested by removing litter at 0, medium, and high level s that resulted in an average residue of coarse litter of 1,171, 787, and 377 kg ha-1. Coarse litter was related to an increase in herbage p roduction (P<0.05) in 3 of the 4 years studied. The effects of litter were related to the growing conditions of each year. The linear regres sion coefficients describing the response (herbage production related to litter) ranged from 0.114 to 0.802 with the smallest effect under e ither very dry or very wet conditions. In Experiment 2, litter was rem oved at high levels in either 0, 1, 2, or 3 successive years. These tr eatments resulted in an average residue of coarse litter of 1,300, 164 , 149, and 188 kg ha-1. Herbage production was not affected by removin g litter for more than 1 year but plant height, tiller weight, and her bage yield of some plant species were.