2012 Annual Report
1a.Objectives (from AD-416):
1. Determine the impact of maintaining cover crops in vineyard alleyways on vine growth and development.
2. Determine the extent of biomass generation of cover crops and nutritional contribution to young vines.
3. Evaluate weed biomass and emergence in vine rows and in alleyways.
4. Evaluate the effects of alleyway cover crop management on soil moisture, rooting patterns of young vines.
1b.Approach (from AD-416):
Pruning weights will be measured at the beginning of the study to establish a baseline of the vine size prior to the treatment season and at the end of each year of the study to determine vine size and vegetative growth of the vines in response to treatments.
Mowing of cover crop will be performed up to two times in a growing season with the first mowing taking place in spring. Treatments will be mowed when the cover crop stand reaches a pre-determined level of biomass appropriate to mulching. Density of cover crop stands will be observed with a random sample taken with a quarter meter square quadrant placed randomly into the treatment. Weed biomass between rows will be evaluated in tandem with cover crop biomass, by manually separating weed and cover crop biomass within the quarter meter square quadrant samples, taken just before mowing.
Soil moisture within the vine row and alleyway will be monitored bi-weekly from mid-June through September using gravimetric soil moisture determination (w/w), with early season measurements in May. Measures from June-September will be concurrent with measurement of vine water use efficiency. Documents Grant with Oregon State University. Formerly 5358-12210-003-13G (8/2011).
A three-year trial is in progress to determine the effects of using cover crop residues to enhance young vine growth and vineyard establishment. The trial is being conducted at a commercial vineyard in the Willamette Valley of Oregon. Each fall, a cover crop mix of cereal rye and crimson clover is sown into vineyard alleyways and grown into the following spring. When the cover crop reaches significant growth and the clover begins to flower, the cover crop is mowed and the residues applied as mulches in the vine row at two densities (1X and 3X rate), placed in the alleyway as is typical for mowing, or removed from the alleyways. Cover-cropped treatments are compared to an unplanted treatment which was never planted to cover crop and kept free of vegetation by tillage and/or herbicide for the duration of the study. The hypothesis is that cover crop residues can be used as mulch within vine rows to conserve soil moisture, reduce weed growth, and increase vine growth through either soil moisture conservation and/or added nutrition. Placement of mowed residue in alleyways or removing it from the experimental plots allowed us to conduct paired comparisons of the data to determine best use methods by which to use cover crop residues.
A winter annual cover crop was managed in the vineyard in 2009-2011. Vine growth has been monitored to determine differences between field treatments. Growth has been quantified through various vine measurements: shoot length, leaf area, fruitfulness, pruning weights, trunk diameters, and root growth. Soil moisture and vine water status have been monitored throughout each growing season to explain any growth differences that may occur. Vine nutrition is assessed through vine tissue samples taken at bloom and véraison (beginning of ripening). In addition, the carbon (C) and nitrogen (N) composition of the cover crop residues is analyzed to determine the potential contribution of the cover crop to the vineyard system. Since mulching can be an effective means of reducing weeds, density and coverage of weed growth was assessed both in the vine row and in the alleyway in the first years two of vineyard establishment.
Results indicate a trend towards increased vine growth with mulching based on increased shoot and root growth, and increased potential yield. Mulched vines also have higher leaf chlorophyll (are greener) as compared to the unplanted treatments, indicating potentially higher nitrogen in mulched vines. However, there were differences in vine nitrogen concentration by treatment in only certain timepoints of analysis (bloom leaf blade N in 2011). Increased vine growth may be due to higher total nutrient content in the mulched vines which are larger despite having similar nitrogen concentrations as other treatments. Greater water conservation and decreased soil compaction may also be allowing increased root and shoot growth in mulched treatments compared to non-mulched treatments. Reductions in weed growth with mulch were observed in 2009 and 2010, and this may also allow for greater vine growth. There was no difference in water status of any of the treatments, indicating that young vines can be managed with a cover crop and without irrigation in similar vineyard sites within the Willamette Valley.
Research continues through the 2012 growing season. The combination of all the years of this research trial will help us better understand how a young vineyard is established and the extent at which these treatments can increase vine health and productivity in establishment years and enhance vine health and sustainability long term. This research was conducted under objective 1B of the parent project.