In California’s dry climate, farmers are often left with a difficult question to answer: are cover crops worth the water? Despite atmospheric rivers, early spring rains and tropical storms causing flooding across the state this year, water conservation remains a top priority for California’s farmers, especially those in more drought-prone parts of the state. With the last two years being some of the driest on record - there is good reason to be water-wise and to plant with care.
The short answer: Yes!
It is possible, and even worthwhile, to add cover crops to your orchard system even in a dry climate. Project Apis m.s’ (PAm.) Seeds for Bees™ program provides free seeds and technical assistance to farmers across California wishing to establish cover crops in their fields. Seeds for Bees™ has partnered with Blue Diamond on the USDA Climate Smart Grant to support Blue Diamond growers to plant cover crops in their orchards. Whether your region gets 35 inches or 5 inches of annual rainfall, we want to help you get the most out of your cover crop planting!
A recent study from University of California Agricultural and Natural Resources (UC ANR) researchers suggest that growers who adopt winter cover crops in the Central Valley “can benefit from soil health advantages associated with winter cover cropping with minimal water use…and without having to change their spring-summer irrigation plans and water management decisions.”1 Cover crops can provide enhanced ecosystem benefits, reduce inputs, and contribute to increased soil quality and conditions. The associated benefits and services from cover crops are certainly worth considering. Researchers also state that “winter cover crops in the Central Valley may break even in terms of actual consumptive water use.”1 If water availability is a concern for your operation, this article provides some general information on water use and helpful guidelines for growing a successful cover crop stand, even in a dry environment.
Why use water for Cover Crops?
Establishing and managing cover crops in California almonds has been proven to add a host of benefits to your orchard system. An effective cover crop system can sustain viable yields while supporting water quality and soil health, reduce inputs and promote biodiversity. Compared to bare soils, cover cropping in orchard alleys can reduce runoff and erosion, enhance infiltration, and even contribute to water saving goals.2 Flowering blooms in almond orchards also provide much needed forage and habitat for pollinators and other beneficial species. Having forage already established and available for bees when they arrive in your orchard sustains and grows healthy bee colonies. More bees means improved pollination services!
Blooming cover crops benefit both beekeepers and growers by providing better nutrition for bees, increasing the soil’s water-holding capacity by adding organic matter, increasing water infiltration, reducing erosion, and providing natural weed control. Photo credit: Project Apis m.
Selecting the right seed mix
Seeds for Bees™ offers seed mixes that are designed to be most efficient for growing successfully in drought conditions. PAm.’s Pollinator Brassica mix is a drought-hardy mix of mustards that can generally grow successfully throughout the Central Valley. This mix is designed to grow in harsh conditions, such as in non-irrigated orchard middles, and has been proven to perform well with annual rainfall – no irrigation needed! If you have higher rainfall or water availability, there are other seed options that do well with a little extra moisture. For instance, PAm.’s Annual Clover Mix and the BioBuild Mix have higher moisture requirements and are well suited for adding nitrogen and biomass into the soil.
Fall planting – timing is everything!
Another consideration for planning cover crops in a dry climate is the timing of planting. PAm. highly encourages growers to sow cover crops within the month of October. Last year, PAm. worked closely with our seed supplier for quick and earlier deliveries and adjusted the Seeds for Bees application window to maximize the number of growers that could plant during this optimal window. In the 2022-2023 Seeds for Bees annual participant survey, 75% percent of growers who responded reported planting in October. Planting within the general time frame of Sept 10 to November 10 is a suitable time to plant cover crops anywhere in California. Planting in time to utilize the seasonal rains can establish a robust, well-growing cover crop stand without the use of irrigation. This time frame ensures suitable soil temps, larger plants, better ground coverage and greater likelihood of timing flowering cover crops with the arrival of hungry honey bees.
While not necessary for an adequate stand, strategic planting times and irrigation can be used to ensure a more robust cover crop. For example, in orchards with micro-sprinklers and flood irrigation, it is best to sow your cover crop prior to tree irrigation. For drip irrigation, plant seed prior to the first rain event. While cover crop seed does require water to germinate and establish, studies have shown that even though irrigated cover crop plots produced about 2x more biomass than non-irrigated fields, non-irrigated cover crops were still productive, meaning growers could still reap the soil health benefits.2 For growers who might also be concerned about lack of irrigation or about cover crops competing for water, The Almond Board’s Cover Crop Best Management Practices Guidebook states it this way: “Cover crops often do not require irrigation after establishment, though they consume water from winter precipitation. Overall, their impact on soil moisture can be negligible because bare soil also consumes water through evaporation and runoff.”3 PAm is also funding additional research at U.C. Davis measuring and comparing water use in orchards with and without cover crops to further understand these dynamics.
Planting cover crops can help increase water infiltration and avoid evaporation and other water losses associated with bare soils. Credit: Almond Board of California’s Cover Crop Guide pg. 12
Rainfall, irrigation methods and water access will vary across region- for some farmers, relying on early fall rains is not always possible. Seeds are dependent on moisture in the top few inches of soil to germinate and irrigation may be needed to achieve a successful stand. Inadequate moisture resulting in low germination will reduce fall growth and ultimately compromise the benefits from the cover crop. For orchards in more arid climates, there are several other options. If you have irrigation, you might consider applying irrigation water to dry soil (until plant emergence) to protect the time and effort you have already invested into your cover crop.4 Another management alternative is to postpone planting, “seeding when there is available water is most important, and later seeding in late winter or early spring as day length increases may still produce a cover crop that can meet your goals.”3 Water use and management decisions, such as when and what to plant, will vary from farm to farm.
Of course, there is no one size fits all for farming. Factors such as your region’s annual rainfall, soil conditions, orchard management practices, etc. will determine what works best for your orchard. Non-irrigated winter cover crops provide a long list of positive benefits while using minimal water to produce a worthwhile return on investment. PAm’s Seeds for Bees™ team offers technical advice specific to your farm and can help you decide what mixes and best management practices are most appropriate for your operation and water use goals.