Regrowth of crested wheatgrass (Agropyron cristatum [L.] Gaertn.) following defoliation

Abstract

] Gaertn.) on the amount of time required to reach peak regrowth, the lag period for regrowth to begin, regrowth biomass, tiller survival and replacement, and carryover effects of defoliation the following year were investigated. Regrowth of crested wheatgrass was determined during the summers of 1990, 1991 and 1992 in central Saskatchewan following a single defoliation to a 5-cm stubble height at eight stages of growth. Crested wheatgrass regrew 54-130 g m -2 of biomass when defoliated tillers had ≤3.6 leaves. Regrowth began accumulating within 3-53 growing degree-days (GDD) and peaked in 705-875 GDD. Rates of leaf development after defoliation (218-252 GDD phyllochron -1 ) equaled or were faster than control (218-330 GDD phyllochron -1 ). Regrowth biomass accounted for 35-76% of total annual production. Total annual production was greatest when plants were defoliated during vegetative growth or at peak growth. In 1991 and 1992, etiolated growth in the spring following defoliation was reduced by defoliation in the previous year. Tiller replacement was not affected by defoliation and averaged 1.2 tillers tiller -1 (SE = 0.1) in 1991 and 1.5 tillers tiller -1 (SE = 0.1) in 1992. Two periods of grazing can be expected from crested wheatgrass if it is grazed when tillers have ≤3.6 leaves; however, the impacts of a second grazing must be determined. If crested wheatgrass is grazed late in the growing season, only one period of grazing can be expected, and production will likely be less the following growing season, necessitating a rest period for plants to regain their production potential. ] Gaertn) sur la durée de repos avant la reprise de la croissance, sur le temps nécessaire pour atteindre la repousse maximale, sur la biomasse de la repousse, sur la survie et sur le renouvellement des talles, ainsi que les arrière-effets sur la croissance l'année suivante. La repousse de la graminée était mesurée au cours des étés 1990, 1991 et 1992 dans le centre de la Saskatchewan à la suite d'une seule fauche à la hauteur de 5 cm, effectuée à 8 stades de croissance. La repousse atteignait 54 à 130 g de biomasse au mètre carré (m 2 ) quand les talles étaient coupées lorsqu'elles ne portaient pas plus de 3,6 feuilles chacune. Elle commençait à s'accroître au bout de 3 à 53 degré-jours de croissance (DJC), pour atteindre son maximum aux alentours de 705-875 DJC. Le taux de croissance foliaire après défoliation, soit 218 à 252 DJC par feuille, était égal ou plus rapide que celui observé dans les parcelles témoins (218-330 DJC). La biomasse de la repousse représentait de 35 à 76 % de la production annuelle totale. Cette dernière était à son maximum lorsque la fauche avait été exécutée durant la phase végétative ou au niveau de croissance maximum. En 1991 et en 1992, la croissance étiolée au printemps suivant l'année de défoliation était diminuée. Le renouvellement des talles n'était pas touché par le régime de fauche et se maintenait aux alentours de 1,2 talles par talle morte (ET = 0,1) en 1991 et à 1,5 en 1992. On peut donc obt...

Impact and management of crested wheatgrass (Agropyron cristatum) in the northern Great Plains

“…Since crested wheatgrass disperses only by seed, controlling seed production will slow invasion. Defoliation is not adequate for complete control (Romo and Harrison 1999). However, defoliation is likely more efficient at controlling crested wheatgrass than are herbicides (Wilson and Pärtel 2003;Hansen and Wilson 2006).…”

Effects of resting perennial pastures during the sensitive pre-dormancy period in western Manitoba: Pasture productivity and beef cattle performance

“…Matches and Burns (1995) indicated that successful stockpiling of both cool-season grasses and alfalfa for late season utilization required a significant rest period without cutting or grazing. Various studies have utilized resting to prevent overgrazing (Romo 2006), reduce fertilizer application and associated soil acidity (Dorrough et al 2004), increase biomass (Dowling et al 1996) and facilitate plant recovery (Romo and Harrison 1999).…”

Divergent effects of defoliation intensity and frequency on tiller growth and production dynamics of Pascopyrum smithii and Hesperostipa comata

“…This suggests that H. comata was able to offset growing season declines in tiller number under frequent defoliation with greater tiller recruitment between years. Romo and Harrison () observed a similar response in Agropyron cristatum , in which defoliation did not increase tiller populations until the following spring. It is also possible that intensively defoliated tillers avoided senescence prior to the end of the growing season and maintained meristem (i.e., basal bud) viability into the following growing season.…”