It is time to get prepared for winter and plant your cover crop. To promote optimal growth, it is best to plant by the end of October, or sooner if possible, while the soil is still warm, and before substantial rains arrive. Cover crops provide many benefits and are one of the four pillars of carbon farming, which also includes using compost, reducing tillage and planting woody plants (hedgerows). They enhance soil health and crop production in several ways including:
- Improving soil structure
- Increasing soil organic matter
- Improving infiltration and water holding capacity
- Protecting soils from damage by sun or rain
- Diminishing evapotranspiration when left on the soil after being cut
- Providing nutrients
- Protecting soils from erosion
- Providing habitat to beneficial insects
- Increasing beneficial biological activity in the soil
- Controlling weeds
There are many types of cover crops and different approaches to using them. Growers should carefully consider their goals when choosing which ones to plant and how to manage them. Different cover crop choices will have their advantages and disadvantages, and tradeoffs need to be considered. Are you trying to control erosion, increase water holding capacity, build up nutrients, or control weeds? Or perhaps you have too much vigor in areas of your vineyard or areas with too much moisture in spring, and you want to use cover crops to moderate that. Determine your priorities to make your cover crop selection, and then make sure that will work for your management program. For instance, you may want to increase nitrogen in your system with legumes like bell beans or vetch, but might have trouble entering your fields until late spring because it is too wet. Then you may want to plant bell beans but avoid vetch, which can grow vigorously, start wrapping into vines and trellises if left in the field too long, and be difficult to cut down. Or perhaps you have sufficient nitrogen in your system but are low in organic matter. Then you want to grow more grasses, such as cayuse oats, barley, or triticale. Likely you are trying to achieve a combination of goals, and using a mix of cover crop seeds will be most useful to you. LeBallister’s OSB Plowdown mix is frequently used in Sonoma county vineyards, but many growers customize their mixes to meet their site specific and agronomic needs. Work with your vineyard manager or crop consultant to determine the best mix for your operation, and/or contact your cover crop vendor to discuss your needs and identify the right ones to use.
Sonoma and Gold Ridge RCDs held a cover crop and tillage tailgate at Ridge Vineyards near Healdsburg in early August, where head viticulturist David Gates discussed their management program, cover crops they use, and shared a variety of ideas on these topics. Participants got to walk in the vineyards, look at the alternate row tillage, see machinery used for planting and cultivation, and see the remnants of their summer cover. Several other experienced viticulturists in attendance shared their perspectives and cover crop and tillage management approach, emphasizing how every site is unique and needs to be managed accordingly.
At Ridge, they generally plant a mix with 50% triticale, 25% bell beans and 25% magnus peas in the alternate tractor rows that are disked. A fescue/subclover mix is planted every other tractor row where it is not tilled. As an organic producer, they try to find organic seed sources, if available, and at a reasonable cost. While they disc every other row, they do not alternate their tilled and untilled rows. Many growers switch their tilled and untilled rows every 1 to 6 years. The tilled rows are seeded before harvest, and the cover emerges after the rains start. This is a good approach for late season grape varieties, where the window to plant might get lost during a late harvest or early rains. Cover crops tend not to establish as well or at all as the soil gets colder in November on. In steeper areas at Ridge ranches, an erosion control mix is planted, and tillage is avoided where it is too steep. Additionally, Ridge plants Hearne Seed’s Low Profile Habitat Blend spiked with lacy phacelia, Queen Anne’s lace and wild carrot. The mix, planted every 8th row in many blocks, and more if possible, provides habitat and food for beneficial insects. The last three plants mentioned are planted at the same time in fall, but don’t bloom until summer, giving insects some late season food.
There are many perspectives, varied approaches and lessons still to be learned about cover crops and tillage. Visit the North Coast Soil Health Hub at www.soilhub.org to learn more about these soil health practices. Keep an eye on this website for postings on soil health topics and upcoming workshops/field days. The RCD plans to offer quarterly events on soil health topics in the field and at indoor meetings during the winter. A great resource is the University of California’s “Cover Cropping in Vineyards” publication. Be aware of CDFA’s Healthy Soils Program as it was just refunded and they will be offering money to growers to implement soil health practices, with the first round of applications projected to begin this fall/winter. You may also be eligible to get cost share funds for cover crops and other soil health practices via the NRCS EQIP program. Contact NRCS at 707-794-1242. Contact Keith Abeles at Sonoma RCD to learn more about soil health practices, carbon farming, and other relevant RCD programs at email@example.com.