One large-plot experiment and a small plot experiment have been established to evaluate the impact of in-row barley cover cropping on soil and water erosion, vine growth and productivity, weed control, and the economics of wine grape production. A 3.5-acre experimental site is evaluating three in-row management practices. The in-row treatments evaluated are:
- Standard, pre-emergent herbicide using flumioxazin (Chateau®) at 0.38 lb a.i./acre + 2% glyphosate with follow-up post emergence applications of 2% lyphosate applied as needed in the summer to control escaped weeds, row middles have a barley cover crop.
- Standard + bare middles.
- Inrow cover crop using barley that was allowed to develop to 12 inches and then burned back with a 2% glyphosate application + 0.38 lb a.i./acre Chateau. A small plot experiment was established, to evaluate the influence of timing of burn-back herbicide sprays to in-row covers.
Rainfall totaled 9.8 inches at the trial site between December 2007 and May 2008. This was double the rainfall of the 2006-2007 winter. Three storm events resulted in 1 to 2 inches of daily rainfall. Run-off amounts for the in-row cover and standard treatments were much less than the amounts measured in the bare plots, which suggest that the cover crop greatly reduced storm run off during the winter. Cover crops reduced nutrient and sediment concentration in the run-off as well as total volume of run-off which effectively reduced sediment, total P, and total N loads by 98&, 94%, and 96%, respectively, compared to the bare plots.
Soil moisture levels were lowest in the bare plots prior to winter rain events. During spring and early summer soil moisture between the large plot treatments was similar. As observed in 2007 a higher soil moisture level was measured in the in- row cover treatment compared to the standard and the bare plots during late summer and fall. The higher soil moisture in the in-row treatment was attributed to the straw-mulch reducing evaporation on the berm and improving infiltration under the dripper. The timing of herbicide applied to the in-row cover significantly affected soil moisture content of the profile with cover crops killed at 24-inches having the lowest soil moisture during March through June.
As observed in 2007 weed impacts were not an issue in 2008 and no significant differences occurred between the treatments. At younger ages the cover crops are more succulent and tend to breakdown more quickly. However, even cover crops sprayed at a young age (i.e. 6 inches tall) still providing significant ground cover into early May.
Soil organic matter in the row was increased with the use of in-row covers. Soil microbial activity in the row was also shown to be increased with in-row cover cropping. Greater soil microbial activity was seen when the in-row covers were allowed to develop higher biomass.
The use of an in-row cover was shown to reduce nitrogen and increase potassium and phosphorus bloom time petiole levels of the vines. The longer the in-row cover is allowed to develop the greater the reduction in nitrogen levels.
The use of in-row covers had no negative effect on the growth and productivity of vines in a fourth leaf vineyard when the cover was burned back at 12 inches in height. A reduction in shoot weight and total vine prunings for the in-row covers allowed to grow for an extending time demonstrated the potential competitive effects of this practice.