Winter peas are a cool-season annual legume used as a cover crop to improve soil health. They are valued for their cold hardiness, allowing them to establish in the fall and survive the winter in many climates. They perform biological nitrogen fixation, converting atmospheric nitrogen into a form usable by subsequent crops. This capability reduces the need for synthetic nitrogen fertilizers, making them an excellent soil-building tool.
Selecting and Preparing the Planting Site
The process of planting winter peas begins with careful site selection to ensure successful establishment. Peas thrive best in a location that receives full sun exposure throughout the day, which encourages vigorous growth before the onset of winter dormancy. While they are adaptable to a range of conditions, the soil should be well-drained, as waterlogging can be detrimental to the plants, especially in colder months.
Winter peas prefer a soil pH maintained above 6.0. Although they can tolerate a wide variety of soil types, light-textured loamy soils tend to yield the best production. Preparing the seedbed can be accomplished through either tilling or no-till methods, but a clean, firm surface is necessary for good seed-to-soil contact for uniform germination.
Applying a specific inoculant to the seeds immediately before sowing is necessary. As a legume, the pea must form a symbiotic relationship with Rhizobium leguminosarum biovar viciae (pea/vetch inoculant). This bacteria creates the nodules on the roots where nitrogen fixation occurs, allowing the plant to draw nitrogen from the air.
The inoculant (a fine powder or liquid) should be mixed thoroughly with the seeds until they are lightly coated. This ensures the seeds have the correct microbial partner to maximize nitrogen fixation for the following crop. Inoculant viability has a shelf life and should be purchased fresh each season for best results.
Timing and Sowing Methods
Planting timing is the most important factor for successful overwintering and biomass production of winter peas. The ideal window for planting is in the late summer or early fall, typically four to eight weeks before the first expected hard frost in your region. This period allows the peas to germinate and establish a strong root system and sufficient top growth before temperatures drop and growth slows down.
A common seeding rate is 45 to 60 pounds of pure live seed per acre (1 to 1.5 pounds per 1,000 square feet). A higher seeding rate is often advisable when broadcasting to compensate for the less consistent seed-to-soil contact compared to drilling. The seeds must be planted at a consistent depth to ensure reliable germination.
The two main methods for sowing are broadcasting and drilling, with planting depth being a critical detail for both. Broadcasting involves scattering the seed evenly over the prepared area, followed by lightly raking or shallowly incorporating the seed into the soil. This crucial step ensures the seeds are covered to a depth of 1 to 2 inches, which protects them from birds and helps maintain moisture for germination.
Drilling, which uses a specialized machine, is the most efficient method as it guarantees the best seed-to-soil contact. When drilling, the depth should also be set to 1 to 2 inches to provide consistent moisture and soil coverage. Planting too shallowly can lead to drying out, while planting too deeply can deplete the seed’s energy reserves before the sprout reaches the surface.
Establishment and Termination
Following planting, the first step for successful establishment is providing adequate moisture to support germination. While winter peas are a cool-season crop, they require sufficient soil moisture to sprout, especially if the seed was broadcast and not fully incorporated. Once established, the plants will grow until temperatures consistently drop, at which point they enter a dormant stage, capable of tolerating temperatures as low as 10°F to 0°F.
Throughout the winter, the plant roots remain active below the soil surface, continuing the process of nitrogen fixation. Above-ground growth resumes vigorously in the late winter or early spring as the soil warms and day length increases. Termination must be timed correctly in the spring to maximize the nitrogen benefit for the subsequent cash crop.
The optimal time to terminate the peas is when they are at the beginning of the flowering stage, but before they start to develop mature seeds. Termination at this point ensures the highest amount of fixed nitrogen has accumulated in the plant tissues and prevents the peas from becoming woody or going to seed. Allowing the peas to reach full bloom can yield over 150 pounds of nitrogen per acre, while early termination may yield only 50 to 60 pounds.
Termination can be achieved through several methods, including mowing, tilling, or roller-crimping. Mowing the peas down to the ground surface is a simple method, leaving the residue to decompose as a nitrogen-rich mulch. Tilling the plant material directly into the soil also works, but leaving the residue on the surface is generally recommended to help retain soil moisture and suppress weeds for the following crop.