Paul E. Read
Date of this Version
Loseke, B.A., 2018. Replacing Herbicides with Groundcovers to Enhance Vineyard Sustainability.
In many Midwestern vineyards a three to four-foot weed-free strip is maintained directly beneath the vines to reduce vine-weed competition. Conventionally, this strip has been conserved with repeated applications of herbicide, mainly glyphosate. The necessity for this weed-free strip to reduce vine-weed competition has been well documented in more arid climates. However, in areas with higher soil fertility and adequate rainfall, this strip may be unnecessary. Moreover, stand establishment and early vine growth have not been well documented when planting groundcovers (GC) immediately following the vine planting. The main objective of this project is to assess the severity of competition for water between ‘Edelweiss’ grapevines and neighboring permanent GC treatments. In year one (2014), the vineyard and GCs were established, where the GCs were planted immediately after the vines. Midday leaf water potential (Ψmd) measurements began in 2015 and lasted through 2017 to assess water competition between vines and GCs. Additional data collected during the four year project included: pruning weights, bud break, yield and fruit quality and soil nutrition. Generally, GC treatments had lower Ψmd than the herbicide sprayed control, however, none of the treatments exhibited even slight water stress. Vine-GC competition was most apparent in the three years of pruning weights, where the most native grass GC treatment had up to 99% in 2014, 193% in 2015 and 183% in 2016 lower weights than the control. Harvest in 2016 and 2017 showed significantly lower yields between GC treatments and the control. However, no differences were found in berry quality (pH, Titratable Acidity, °Brix). An additional greenhouse project was done to define water stress thresholds for ‘Edelweiss’ grapevines using Ψmd and high resolution thermal infrared images. Fully irrigated and 14-day dry vines exhibited a Ψmd of -8.7 bars and -13.3 bars, respectively. The grapevines exhibited a mild, moderate and severe water stress level at 8, 10 and 12 days-dry, respectively (Ψmd of -12 bars, -12.5 bars and -13 bars). Results suggest that planting groundcovers in both the alleyways and in-row areas of the vineyard during the first year of establishment is detrimental to vine growth and causes reduced yields.
Advisor: Paul E. Read