Enhancing Cover Cropping Opportunities with Spring Cover Crops

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Part II: Planting Spring Cover Crops

By Chuck Schembre, Understanding Ag, LLC

In the fall of 2023, NM Healthy Soil partnered with Green Cover Seed to distribute one hundred 25-pound bags of a custom designed spring cover crop seed mix among attendees at the annual REGENERATE Conference, taking place in Santa Fe, New Mexico. This article is the second in a three-part series providing guidance on how to plan, plant and harvest a diverse spring cover crop in the Western United States. Click here to read the first article.

Image by Green Cover Seed

Establishing a Diverse Spring Mix

Given the broad audience of farmers and ranchers reading this article, this discussion will be generalized however, the most important consideration when planting cover crops  is to ensure that the seed has decent seed to soil contact or that there is plenty of residue on top or mixed with the seeds to hold moisture and prevent seed desiccation. 

Soil microorganisms play a critical role in the success and resilience of seed germination. In healthier soil, with good soil aggregation, organic matter, residues, and water holding capacity, seed to soil contact is therefore not as important, while in bare and compacted soils, ensuring good soil contact and seeding depth is imperative. 

If you are sowing into degraded/poor soils, I recommend inoculating the seed with a bio-inoculant containing fungal and bacterial organisms, combined carbon rich bio-stimulants, such as humic and fulvic acids, compost extract or tea, and sea products. Inoculants are likely not necessary if you have very good soil health and plenty of soil armor and residue.

When deciding on the timing of seeding and what method of seeding to use, consider your context and general rainfall patterns. Given the majority of the audience reading this article lives in the arid-west, Spring time does not always provide good precipitation, especially late Spring. Direct seeding will always provide better seed to soil contact, and reduced chance of seed desiccation. However, broadcast seeding can be very effective if there is plentiful moisture, either from rain or irrigation, and if the seed has good residue coverage, or is being overseeded into an existing field or plot with vegetation. If seeding to a very bare and compacted site, direct seeding is the best choice. If you do not have access to a seed drill, you can broadcast seed to bare soil, where it must be mulched with straw, or lightly incorporated into the soil to guarantee success. In general, an application of straw or hay mulch over bare ground will provide the greatest success with seeding.

Seeding Considerations

The mix designed for NM Healthy Soil’s spring cover crop seed campaign (see sidebar) is suggested to be seeded at approximately 50 lbs per acre to an open field with little to no vegetation. Many of the species in the mix are very small seeded and less than one pound per acre can provide hundreds of thousands  of seeds per acre. For example, all the brassicas, clovers, safflower, and phacelia should be seeded at no more than 1 lb per acre. This is important or you may find the seeded area becomes dominated by these few species even at 2-3 lbs per acre of each. If overseeding an existing field, the rate could be dropped to 25-30 lbs, and if broadcasting to an open recently tilled field, the rate could be increased a bit to 60 lbs.

Most of these species in the mix can be seeded into cool soils, with a recommended minimum soil temperature of 40-45 °F. The majority of these species can handle light frost or slightly below freezing temperatures, with the clovers and vetch being the most cold weather tolerant. To guarantee good germination and success, it is recommended to seed two weeks before or at the last frost date as long as the soil temperatures have warmed up.

1. Spring Forage Pea
2. Common Vetch
3. Crimson Spring Lentil
4. Kentucky Pride Crimson Clover
5. Balady Berseem Clover
6. Cosaque Black Oats
7. Lavina Beardless Spring Forage Barley
8. Nitro Radish
9. Trophy Rapeseed
10. Purple Top Turnip
11. Brown Flax
12. Baldy Safflower
13. Super Bee Phacelia

List of species that comprised the mix designed for NM Healthy Soil’s spring cover crop seed campaign. For more detail about this cover crop mix, read the first article in this series.

Direct seeding a cover crop at Tony’s Farm, NM Healthy Soil Field Day in Hernandez, 2023. Photo by I. Jenniches CC BY 2.0

Direct Seeding

Direct seeding is the “King” or “Queen” of seeding methods. However, most small farms do not have a tractor driven grain drill or no-till drill. A seed drill is the preference for seeding anything larger than a large garden, and with savvy ingenuity, one could modify an old corn or bean drill to work. If using a grain drill, whether no-till or a standard drill, all the seed can be applied from the main seed box. If the drill has multiple seed boxes, it is not necessary to separate the seed by size, and the smaller seed will remain mixed in suspension very well.

The seeding depth should be equal to the maximum depth of the smallest seed. For example, brassica seeds (radish, turnip and rapeseed), are the smallest seed sizes in this mix, and should not be seeded much deeper than ½ inch. Some of the larger seeds, like Spring Pea, have a suggested minimum depth of ¾ inch. Now, as you can see, these seeding depth differences create a bit of a conundrum when selecting the ideal seeding depth for a diverse mix, however I have found a ½ – ¾” depth will provide good germination for all the species collectively.  

For the market gardener or homesteader, you may be seeding a small area or garden beds, and a push behind hand seeder such as an Earthway seeder can be very effective, albeit time consuming. If you are using a hand seeder, target the same depth of ½ – ¾”.  Gardeners may find more enjoyment with broadcast seeding.

Hand broadcasting cover crop seed, NM Healthy Soil Field Day in the Village of Los Ranchos, 2022. Photos by Isabelle Jenniches CC BY 2.0

Broadcast Seeding

Broadcast seeding works well, but can also go wrong real quick when certain steps and considerations are not made. As mentioned earlier, for broadcast seeding to be successful there are two critical pieces that must be in place, 1) adequate moisture following seeding (rain or irrigation), 2) good residue, mulch, or vegetation coverage to retain moisture and prevent desiccation. 

The third most important component is to increase the seeding rate by 25% minimum of the direct seeding rate. Or in other words, seed at the highest suggested rate for the mix you are using and do not be afraid to throw out a bit more. 

Broadcast seeding is quick and easy, and the equipment required is relatively inexpensive, making it the most desired choice for many folks. A basic 3-point mount cone spreader can be easily found locally at most tractor or farm supply shops. For the market gardener or homesteader, a small chest mounted spreader will do the trick, or simply hand broadcasting in the home garden.

In the next article we will discuss options and considerations for harvesting a spring cover crop. Stay tuned!

Happy cover crop seed recipients at the 2023 REGENERATE Conference. Photo by Isabelle Jenniches CC BY 2.0

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