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.

VARIETIES

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.

SOIL

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.

SOIL TEMPERATURE

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.

INOCULATION

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.

FERTILIZER

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 and soil sample bags and information sheets.

Nitrogen (N)

Rates of 15 to 20 lb N/A banded with P and possibly K at planting time are suggested. Peas have the capability of fixing atmospheric N, and have been shown to utilize this more efficiently than soil applied N. The additions of N to the soil at rates higher than indicated may inhibit nitrogen fixation and actually result in lower yields.

Information on the application of N is given below in the sections on P and K.

Phosphorus (P)

Phosphorus is essential for vigorous early growth of seedlings. Preferably P, N, and, where required, up to 60 lb K2O/A should be applied in a band 2 inches to the side and 2 inches below the seed at planting time.

When banding equipment is not available, 15 to 20 lb N/A and 40 to 75 lb P2O5/A can be drilled with the seed. Do not use urea or diammonium phosphate as N and P sources when fertilizer is drilled with the seed. Additional P2O5 and K2O, when required, can be broadcast and plowed down before planting.

          If the soil test*             Apply this amount of
          for P reads (ppm):          phosphate (P2O5) (lb/A):
                0 - 10                        40 - 120
               10 - 20                         0 -  60
               over 20                           None

Potassium (K)

Soil testing should be used to evaluate the need for K fertilizer.

      If the soil test*          Apply this amount of
      for K reads (ppm):              K2O (lb/A):
            0 -  75                    90 - 120
           75 - 150                    60 -  90
          150 - 200                    40 -  60
           Over 200                      None

Potassium should be applied and plowed down before planting or banded at planting time. Potassium should not be included with N and P when fertilizer is drilled with the seed. In a 2" x 2" band application of N, P, and K, the K rate should not exceed 60 lb K2O per acre. Additional K, where required, should be broadcast and plowed down prior to planting.

Seedling injury from banded fertilizers tends to be more serious:

- in drier soils
- in coarse textured, sandy soils
- where fertilizer band is close to seed.

Superphosphate fertilizers are less injurious to seedlings than N and K fertilizers. Urea and diammonium phosphate can be particularly injurious if placed too close to the seed.

Sulfur (S)

Plants absorb S in the form of sulfate. Fertilizer materials supply S in the form of sulfate and elemental S. Elemental S must convert to sulfate in the soil before the S becomes available to plants. The rapid conversion of elemental S to sulfate is dependent on warm, moist soil conditions. This reduces the effectiveness of elemental S as a sulfur source for early planted annual crops.

The S requirements of peas can be provided by the application of 20-30 lb S/A in the form of sulfate at planting time. Because many commonly used fertilizer materials contain significant amounts of S, a separate application of S may not be needed.

Other Nutrients

Responses of peas to nutrients other than those discussed in this guide have not been observed in eastern Oregon. Peas have a comparatively low requirement for boron, which should never be included in fertilizer banded with peas.

The response of peas to fertilizers is dependent on the amount of water available to the growing crop. The higher rates of fertilization are suggested where plant growth and yield are not limited by water during the growing season. Where restricted water supply does limit plant growth the lower rates of fertilizer are suggested.

Lime

Significant responses of peas to lime have not been observed in eastern Oregon. Peas are sensitive to soil acidity, however, and the application of lime at 1 to 2 T/A may be considered when the soil pH is below 6.0. Lime should be applied at least several weeks before seeding and mixed with the surface 6" of soil. A lime application is effective for several years.

Fertilizer Guide #3, "Liming Materials for Oregon," which is available from your local OSU Extension Office, provides additional information on lime.

The above fertilizer recommendations are based on soil test values from the OSU Soil Testing Laboratory and on research conducted by Crop and Soil Science and Horticulture Departments faculty, and is quoted form Oregon State University Fertilizer Guide FG 72.

IRRIGATION

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.

1. 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.

2. 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.

3. Peas do not generally respond to irrigation after flower petals begin to fall, and irrigation at this stage may increase disease incidence.

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.