Abstract:
The use of grass cover crops is a recommended practice in
nonirrigated vineyards in the Willamette Valley, Oregon. Two
studies were initiated to investigate the competitive and
noncompetitive effects of grass cover crops on the growth and
development of Pinot noir grapevines. Two greenhouse pot culture
experiments were performed to investigate the allelopathic potential
of cool season grasses. In the first experiment grass and
uncallused grapevine cuttings were established simultaneously in 4
liter pots filled with sand with no fallow strip. Water and
nutrients were supplied at luxury levels so as to be nonlimiting.
Differences in rooting and growth of the grapevines was a function
of the growth habit of the grass. Allelopathy was not apparent.
In the second greenhouse experiment perennial ryegrass (Lolium
perenne cv.'Elka') was established in 15 liter sand:peat filled
pots before uncallused grapevines were planted directly in the
grass. Water and nutrients were supplied at luxury levels. Root
initiation was inhibited under the ryegrass, with only 24% of the
cuttings initiating rooting. Allelopathy may have been involved.
A 2 year field study was also initiated to investigate the
consumptive water use of 4 cool season grasses (L. perenne, A.
tenuis, F. arundinacea. and D. glomerata) used as cover crops in
Oregon vineyards under low maintenance conditions. Seasonal evapotranspiration
and total depletion of soil water did not differ
significantly among species, and was significantly greater than
bareground in the early summer months. In late summer months
evapotranspiration of the grasses was not significantly different
than evaporation from bareground. Establishment of unrooted
grapevine cuttings placed directly into established perennial
ryegrass turf is unlikely to be successful. Once vineyards are
well established, grass cover crops can provide benefits to the
vineyard without strong competition for soil water during the
summer months.
