Last revised February 12, 2010
Peas in eastern Oregon are grown in the Blue Mountain area east of Pendleton to Milton-Freewater, mostly as dry-land production in rotation with wheat. More recently production has also been in the Hermiston area where soils may be more sandy and subject to wind erosion. Hermiston area production may be irrigated or non-irrigated.
Freezing and canning varieties differ in a number of characteristics. In general, freezers are darker green due to the presence of green color in the seed coat. Seed may either be wrinkled (freezers) or smooth (canners). Varieties may be also classified by sieve size, with small-sieve peas being important for freezing and becoming more popular in general. The development of dual-purpose varieties are making these distinctions less important.
More recently, modified-leaf varieties have become available. The afila type is a semi-leafless mutant where the leaflets have been converted to tendrils. Stipule leaves are still present. This plant habit makes possible an open plant structure that favors good aeration, growth habit, better light penetration, and improved color, especially important in freezer peas. The upright plant habit improves harvest recovery and efficiency.
Processing: Processors will specify varieties for each planting period.
In eastern Oregon, varieties used are: Venus, Dual, Bolero, Midget, Stampede (afila), Misty, Athena, Virtue, Dignity, Puget, Dark Seeded Perfection. For trial: Genie, Karisma, and Tacoma (afila types); Darien, Encore, Green Arrow, Kalamo, Knight, Lazor, Maestro, Prism, Talbot.
It is important to choose a field with uniform fertility, soil type, slope, and drainage to get a uniform pea crop. The best soils are silt loams, sandy loams, or clay loams.
Peas need a good supply of available soil moisture, but yields may be reduced by over-irrigating as well as under-irrigating. Peas grown on wet soils develop shallow root systems which cannot supply the plant's water requirements when the soil dries out later in the season. Root rot is often a problem in wet soils.
Determine corrective lime and fertilizer needs by a soil test. Adjust pH to 6.5 or higher for maximum yields.
Germination will occur from 39 to 85 F. Optimum temperature is 50-75 F.
LAND PREPARATION AND SEEDING
The land should be plowed, harrowed and a cultipacker used lightly to ensure a firm seed-bed. The land should be level in order to make harvesting more efficient. After seeding the land may be cultipacked again to smooth the surface and insure good moisture movement to the seed.
In the lower Columbia Basin, (Hermiston, Milton Freewater and Walla Walla areas), pea planting begins in late February, and ends about mid-May at the higher elevations along the foothills of the Blue Mountains. Processing peas are scheduled on the basis of accumulated heat units, taking into effect regional elevations, slope directions and cultivar differences. Also, each processing company uses 3 or 4 varieties of each maturity group (early, mid-season and late maturity) to spread the harvest season. Planting and harvest schedules are established by the processing company.
Scheduling plantings for orderly harvest of each variety is accomplished by the use of the accumulated heat unit (AHU) system. This is defined as the accumulated difference between the base temperature for crop growth and the mean of the daily maximum and minimum air temperatures. The AHU system information combined with selection of appropriate early and main season varieties, and with field selection based on elevation has been effective in pea production scheduling. Using a 40 F base, early varieties currently used require about 1200 heat units and late varieties about 1500 heat units to reach a 100 tenderometer maturity in Umatilla County. Whether production fields will be irrigated or non-irrigated also has important variety selection and planting schedule implications.
Pea seed numbers approximately 90-175 per ounce. Drill dwarf types for processing at a uniform depth of l.5-2 inches into moisture, dropping 3 to 6 seeds per foot of row with rows 6-8 inches apart.
Aim for a plant population of 480,000 plants per acre, avoid excessive overlaps and double planting along the edges of the field. This may cause uneven colored peas and lack of uniformity at harvest. The new small-seeded varieties must be planted shallow in order to obtain the best stands. These peas are less vigorous than the standard types, and for that reason they need to be planted where moisture is close to the surface, and in the more fertile fields.
Providing moisture is adequate and not excessive, a light rolling may be advantageous. Heavy rolling or packing is likely to reduce root growth, fertilizer uptake and pea root nodulation, and to increase the number of plants affected by root rot.
Inoculate with Rhizobium bacteria in a planter box treatment when planting on soils not previously cropped to peas.
Pea seed should be inoculated immediately before seeding to insure an adequate supply of nitrogen-fixing bacteria. A fresh, effective, live culture of the correct strain of Rhizobia should be used. The need for inoculation is reduced in fields that have been used for a pea-wheat rotation for several years and where pea yields have been satisfactory.
Good management practices are essential if optimum fertilizer responses are to be realized. These practices include use of recommended pea varieties, selection of adapted soils, weed control, disease and insect control, good seed bed preparation, proper seeding methods, and timely harvest. Because of the influence of soil type, climatic conditions, and cultural practices, crop response from fertilizer may not always be accurately predicted. Soil test results, field experience, and knowledge of specific crop requirements help determine the nutrients needed and the rate of application.
The fertilizer application for vegetable crops should insure adequate levels of all nutrients. Optimum fertilization is essential for top quality and yields. Recommended soil sampling procedures should be followed in order to estimate fertilizer needs. The Oregon State University Extension Service agent in your county can provide you with soil sampling instructions.
See the following Fertilizer Guide for Peas- Eastern Oregon for fertilizer recommendations.
Peas are produced successfully with or without irrigation depending on the area of production and cropping practices. In the irrigated area around Hermiston where center pivot systems are available, peas may be conveniently and economically irrigated, taking advantage of the large response peas exhibit to irrigation. However, timing is important.
In the Milton-Freewater and Athena areas, do not irrigate peas before flowering unless the ground is very dry and germination would not otherwise occur, or the crop is severely wilted. Irrigation at this time may actually decrease yield. This caution does not apply to the sandy soils in the Hermiston area.
Irrigate when flowers are first opening. This is when peas are most responsive to irrigation because root growth ceases and demand for moisture is high.
Peas do not generally respond to irrigation after flower petals begin to fall, and irrigation at this stage may increase disease incidence.
HARVESTING AND HANDLING
Peas in the lower Columbia Basin (in the Milton Freewater/Walla Walla area) are harvested from about late May through late July. The peak harvest season is from mid June to mid July.
Yields in the Hermiston area are much better than in the main growing area (around Milton Freewater and Walla Walla) because of new ground, center pivot irrigation and because the early peas there are harvested before the hot weather hits. Plantings in the Hermiston area bloom during more moderate temperatures.
Yields in the Hermiston irrigated area are in the 2 to 3 ton per acre range. In the Milton Freewater-Walla Walla area the average yield is about 1.25 tons per acre, largely unchanged in the past 25 years. Yields may range from 600 to 6000 lb/acre! The best yields occur in late June, before hot weather prevails.
The processor determines time of harvest according to tenderometer reading, the number of other fields ready for harvest, weather, soil conditions, and the processor's need for quality. Yields of shelled peas increase with increasing maturity, but quality decreases.
With mobile viners the crop is cut and swathed into windrows, threshed out by the mobile viners following swathers. Peas must be delivered to the processing plant soon after harvest, especially when the weather is hot, to avoid off-flavors. With the new pod stripping harvesters, no swathing is needed.