Cover crops are an increasingly popular way for almond growers to contribute to long-term pollinator health in their orchards as well as potentially deal with a range of issues affecting the soil.
And while much of the attention over the past few years has focused on the benefits cover crops provide to honeybees, the possible improvements to soil health can be equally compelling for many growers.
The Almond Board of California is proud to have funded research into all aspects of cover crops. That investment has led to the development of the Cover Crop Best Management Practices (BMPs), an easy-to-follow guide that covers everything any grower might want to know before introducing the practice into his or her orchard.
The BMPs are the result of almost a year of conversations, which followed a multi-year research project and extensive literature review of research on cover crops in orchard systems. In addition to growers, others who contributed to the BMPs include the UC Cooperative Extension, Natural Resources Conservation Service, the Lockeford Plant Materials Center, Project Apis m., the Community Alliance with Family Farmers and The Xerces Society.
Dr. Vivian Wauters, a postdoctoral scholar at UC Davis, was one of the lead authors of the BMPs. She recently addressed some of the basics found in the guidelines.
What are the five steps to cover crops?
- Planning: This is incredibly important, Waters said, because of the extent to which growers carefully plan – which means doing things like gathering information from extension specialists and other growers, defining their goals and operational constraints, purchasing seeds, making sure that they have the proper equipment and being prepared ready to plant when they will have precipitation to help with germination – these things can have a big impact on how successful their cover crops will be.
- Planting: This is all about timing – both planting when there will be water to help with germination and also when growers have time within their fall/winter orchard management.
- Growth period: This is when growers will see whether their planning was effective to get a good stand and when they must monitor the cover crop for pest issues.
- Termination: This is when the cover crop is killed. Wauters said the timing of this will vary based on the orchard system, and the guide has information to help growers decide when is best for them.
- Post-termination until harvest: During this time, growers will want to manage residue from the cover crop so that it doesn’t interfere with harvest as well as start to plan for the next season. This final step feeds into the first step of planning, Wauters explained, which includes critically evaluating what went right/wrong and using that to inform future plans.
What are the primary potential benefits to soil health?
Soil health includes physical, biological and chemical aspects of the soil ecosystem. Cover crops can affect all of these. Wauters said studies of cover crops in California since the 1920s have found that they improve soil structure, which means a reduction in compaction, soil sealing, cracking and improved water infiltration. Cover crops also can support biological soil ecosystems, such as fungal networks. All of these improvements in soil health can help with input needs and use, and dealing with perennial concerns many growers face such as salinity buildup and compaction.
Wauters said that building soil organic matter and sequestering carbon – which is often what people think of first with soil health – is unlikely by just adding annual cover crops that are terminated and decompose fully before harvest. She said the integration of very diverse cover crops with other practices – compost applications, whole orchard recycling or livestock grazing – can have more lasting effects on these aspects of soil health.
How can cover crops help bees?
When flowering, cover crops can provide bees access to more diverse nutritional resources, which can improve their health. Wauters said this is true for the honeybees placed in the orchard for pollination and, later in the spring, wild bees. There have been concerns that flowering cover crops will distract bees, but the evidence so far does not indicate that to be an issue, she said.
Wauters offered two caveats. First, the cover crop will provide no benefits to bees unless it is flowering. To have flowers for honeybees during almond bloom means the cover crop should be planted by mid-November and watered (either rainfall or irrigation) for prompt germination. Second, growers need to do all they can to minimize other risks to bees. ABC has Best Management Practices for honeybees goes into more detail on how to protect and promote honey bee health.
Is there a learning curve for growers who haven't planted cover crops before?
Growers often say that cover crops are more successful as they get more experienced with using them. Wauters said there are many aspects of cover cropping that will be specific to any orchard and figuring out the best management practices for that specific situation may take some time. However, the BMPs can provide a baseline of some common and well-supported easy-to-implement options for cover cropping during the winter.
What else should growers know to make an informed decision?
Wauters said cover cropping is just one tool to consider within the context of any orchard system and, depending on circumstances, it may not be the best tool for every goal. The guide is intended to help growers think through how to make it work, and especially think about how cover crops help transform the canonical bare soil orchard, which is often highly productive at the expense of other things, like pollution mitigation and resilience in the face of climate change. Also, it’s important for growers to know that the research community does not have all the answers about how to best use cover crops in every circumstance. As it continues to do more research and to learn from growers about what has worked for them, some of the recommendations may change.
Find out more about cover crops and download the new resource at Almonds.com/CoverCrops.
