Selecting and Managing Vineyard Cover Crops to Reduce Consumption of Net Basin Water

Objective 1: Evaluate five cover crop species for their impact on water infiltration, soil moisture retention, and use of plant available water in the vineyard.

Experimental Design

Three sites for the experiment were selected in vineyards owned by J. Lohr Vineyards and Wines, Opolo Vineyards, and Niner Wine Estates. All three site were along the “46 East” corridor encompassing the border between the Paso Robles Estrella District and Paso Robles Geneseo District AVAs east of Paso Robles, California. The experimental designs were randomized complete block designs consisting of five treatments plus a control in three blocks (See Figure 1 for an example of the experimental design). The treatments were different species of cover crops planted at the recommended rate per acre within the experimental plot (Table 1). The control for comparison was “clean cultivation” which was executed as disking the plot at the same time the other plots were prepared as seed beds, but nothing was planted. These plots were not disked again until after data was collected. It was not practical to disk the control plots multiple times during the winter, so there was weed growth. This does reflect what a grower practicing a clean cultivation program would do as they would not cultivate during the winter. The species of cover crops planted were Blando Brome, Barley (UCD 937), Triticale (Trios 888), Peas (Dundale), and Medic (Parragio). All seed and planting services were provided by Helena Chemical Company.

Experimental plots consisted of the middles (or “tractor avenues”) on either side of a vine row. The width of the plot including the vine row was 20 feet. The length of the plot was nine vines equaling either 45 ft. or 54 ft. depending on vine spacing. The total area of the experiment equaled about 0.40 acres at each site. All data were collected from the area around the middle three vines of the experimental plot. Experimental plots were marked in the field using flagging tape. The same cover crops were planted in the same plots in November 2014 and November 2015. Samples for measuring plant biomass and soil moisture were collected in late April/early May of both years.

Data Collection

It was not possible to collect data from one of the sites in either 2014 or 2015. In the first year, the area was mowed before data could be collected. In the second year, the cover crops did not germinate. At another site it was not possible to collect data from the experiment in 2016 because the area was mowed and disked before samples could be collected. Therefore, there is data for analysis and comparison from two sites in 2015 and one site in 2016. In April 2015 and April 2016 samples were collected from the experimental plots at the available sites using the same protocols providing comparable data, and therefore, comparable statistical results.

Plant samples were collected from each plot using a 20” X 20” quadrat thrown at random into the plot. All plants originating from within the quadrat we clipped at approximately 1” above the soil surface and collected in paper bags. This was done three times in each plot yielding three subsamples per plot. The bags containing the plant material were dried at 100°C in a forced air drying oven for 24 hours. Samples were then weighted to determine dry matter reported in grams per square meter.

Soil samples were taken at 18” and 36” on one side of the vine row near the halfway point of the length of the plot. Samples were placed in plastic bags. Forty grams of soil were weighted into a sample can and were dried at 100°C in a forced air drying oven for 24 hours. Samples were then weighted to determine gravimetric soil moisture reported as a percentage.

To determine if there were any effects of the treatments on the growth of the vines in the experimental plots, cane counts and cane weights were taken in January of 2016. Of the three cover crop species experiment sites, two had pre-pruned the experimental area before data could be collected leaving one site for cane data collection.

To collect the data, three vines in the middle of each plot were chosen as data vines. All canes originating from the cordon or trunk of the vine at or above the head were counted and recorded. Then all cane material from those points of origination was collected and weighed. This information was used to calculate average cane weights.

Statistical Analyses

Data were analyzed using ANOVA in SPSS Version 24. Treatment and block were included in the models and Tukey’s HSD at the 0.05 level of significance was used to separate significant means.

Objective 2. Evaluate treatments to suppress and terminate cover crops and their impact on water infiltration, soil moisture retention, and use of plant available water in the vineyard.

Experiment Design

Three sites for the experiment were selected in vineyards owned by J. Lohr Vineyards and Wines, Derby Wine Estates, and Treasury Wine Estates. All three sites were along the “46 East” corridor along the southern border of the Paso Robles Estrella District AVA east of Paso Robles, California. The experimental designs were randomized complete block designs consisting of five treatments plus a control in three blocks (See Figure 2 for an example of the experimental design). The treatments were different timings and methods of terminating a Blando Brome cover crop in the spring (Table 2). The control for comparison was “clean cultivation” which was executed as disking the plot at the same time the other plots were prepared as seed beds, but nothing was planted in the same manner as the control plots in the cover crop species experiment described above. The plots of the no-till treatment were not disked at any time during the period of the experiment. For the other treatment plots a seed bed was prepared and they were planted with Blando Brome at 25 lbs./per acre. All seed and planting services were provided by Helena Chemical Company. The treatments in the experiment were 1) No-till, 2) mow 30 days after bud break, 3) mow at bud break, 4) mow and disk at bud break, 5) chemical mow with glyphosate at bud break, and 6) the unplanted control.

Experimental plots consisted of the middles (or “tractor avenues”) on either side of a vine row. The width of the plot including the vine row was 20 feet. The length of the plot was nine vines equaling either 45 ft. or 54 ft. depending on vine spacing. The total area of the experiment equaled about 0.40 acres at each site. All data were collected from the area around the middle three vines of the experimental plot. Experimental plots were marked in the field using flagging tape. The same treatments were executed in the same plots in 2014 and 2015 with the cover crop being planted in November and the treatments being executed in late March/early April of each year. Samples for measuring plant biomass and soil moisture were collected in late April/early May of both years.

Data Collection

It was possible to execute the experiment and collect data from all three sites both years. In April 2015 and April 2016 samples were collected from the experimental plots at the three sites using the same protocols providing comparable data, and therefore, comparable statistical results.

Plant samples were collected from each plot using a 20” X 20” quadrat thrown at random into the plot. All plants originating from within the quadrat we clipped at approximately 1” above the soil surface and collected in paper bags. This was done three times in each plot yielding three subsamples per plot. The bags containing the plant material were dried at 100°C in a forced air drying oven for 24 hours. Samples were then weighted to determine dry matter reported in grams per meter.

Soil samples were taken at 18” and 36” on one side of the vine row near the halfway point of the length of the plot. Samples were placed in plastic bags. Forty grams of soil were weighted into a sample can and were dried at 100°C in a forced air drying oven for 24 hours. Samples were then weighted to determine gravimetric soil moisture reported as a percentage.

To determine if there were any effects of the treatments on the growth of the vines in the experimental plots, cane counts and cane weights were taken in January of 2016. Of the three cover crop termination experiment sites, two had pre-pruned the experimental area before data could be collected leaving one site for cane data collection.

To collect the data three vines in the middle of each plot were chosen as data vines. All canes originating from the cordon or trunk of the vine at or above the head were counted and recorded. Then all cane material from those points of origination was collected and weighed. This information was used to calculate average cane weights.

Statistical Analyses

Data were analyzed using ANOVA in SPSS Version 24. Treatment and block were included in the models and Tukey’s HSD at the 0.05 level of significance was used to separate significant means.