Results of 2017 WSU-Mount Vernon Grain Pea Trial

Author: Dr. Susan Kerr, WSU NW Regional Livestock and Dairy Extension Specialist

Publish Date: Spring 2018

Livestock producers such as dairy farmers feed their animals complex rations, usually on a least-cost nutrient basis. This means they meet animals’ nutritional requirements using the most cost-efficient feeds they can obtain. This addresses two aspects of farm sustainability: animal welfare (meeting animals’ nutritional needs) and financial success (reducing expenses to increase profitability). Livestock nutritionists are constantly adjusting the rations their clients feed based on the cost and availability of ingredients; farmers make recommended ration changes gradually to not upset critical populations of intestinal digestive microbes.

The Problem

The preceding background information was presented to help readers understand a regional dilemma: dairy farmers have come to rely on canola meal for ration balancing, but it has become increasingly more expensive and less available. Canola meal is a valuable by-product of the canola oil seed industry, containing 28 to 42% crude protein, depending on processing (Table 1.) However, its cost has risen from $112/ton in 1998 to $350/ton in 2018 (USDA ERS, 2017; USDA AMS, 2018). Also, it must be trucked into northwestern WA either from eastern WA or Portland.

A Little about Peas

Dry peas (a.k.a. field peas, Photo 1) are a cool season annual crop well suited to northwestern WA. They can be seeded directly into previous crop residue in mid-March to mid-May or whenever soil temperature is over 40°F (O’Neal, 2017). Cold-tolerant varieties can be planted in the fall as a cover crop or to produce dry peas for livestock or humans. In areas with dry summers, fall planting can result in higher yields due to earlier spring growth, earlier bloom, and earlier harvest; there will be more nitrogen fixation, as well (O’Neal, 2017).

In Washington State, 90,000 acres of dry edible peas were planted in 2016. They yielded an average of 2.4 tons per acre, brought an average of $12.30/cwt, and were valued at $317 per harvested acre (Mertz, 2017).

Variety TDN % CP % NDF % ADF % Fat % Starch %
Fava 78 30 19.0 10.0 4.5 36.0
Flex 78 22 19.0 9.0 4.0 39.0
Admiral 79 22 13.0 8.6 4.0 39.0
Dundee 78 25 21.0 11.0 3.5 35.0
(canola meal)* 72 - 75 28 - 42 12.9 - 25.4 9.7 - 16.2 2.0 - 19.5 5.1

Table 1. Comparison of chemical analysis results: 2017 pea variety trial and canola meal values.

*Provided for comparison to peas. Nutritional content depends on process used to extract oil. Sources: Neibergs et al., 2016 and Canola Council of Canada, 2015.

TDN – total digestible nutrients; an overall measure of energy contained in a feedstuff, CP = crude protein, NDF = neutral detergent fiber; low number desirable and associated with greater feed intake by livestock, ADF = acid detergent fiber; low number desirable and associated with higher feed (fiber) digestibility

Benefits of Peas

Peas have the potential to be a beneficial rotational crop for many reasons:

  • They are an alternative to summer fallow and another option for crop rotation
  • Peas can be inter-seeded with corn, oats, barley, or other crops to boost protein content of hay and haylage
  • They are a legume and will fix atmospheric nitrogen to improve soil fertility
  • Peas have a taproot that can help reduce soil compaction and improve water and nutrient movement
  • They can mature by mid-August so a fall crop or cover crop can still be planted
  • Peas can be combined to save harvesting labor; equipment is available locally
  • Post-harvest aftermath can be baled, tilled in, or grazed
  • The low moisture of dry peas facilitates long-term storage as a feed commodity

Are Peas the Answer?

Hoping for a high-protein feedstuff they could grow locally for more control over price and availability, dairy producers in northwestern WA wondered about the suitability of dry peas. Peas were grown in northwestern WA for decades until local processing ceased around 2010. Nevertheless, pea planting and harvesting equipment is still available in the area, as are growers with experience in and historical knowledge of pea production. Could these resources support a mini-resurgence of the northwestern WA pea industry as a source of high protein livestock feed?

Variety Planting rate Planting date Harvest date Precipitation over growing season Production (tons/acre)
Admiral 200 lbs/acre 05/10/2017 08/18/2017 2.45" 2.5
Dundee 200 lbs/acre 05/10/2017 08/18/2017 2.45" 1.5
Flex 200 lbs/acre 05/10/2017 08/25/2017 2.45" 1.9
Fava 180 lbs/acre 05/10/2017 09/15/2017 2.73" 2.4

Table 2. WSU-NWREC 2017 pea variety test plot details.

SU-NWREC 2017 Pea Variety Trial

Faculty at the WSUNorthwestern Research and Extension Center (NWREC) conducted a dry (grain) pea variety trial in 2017 with three pea varieties and one bean variety. Funding was provide by the Northwest Agricultural Research Foundation ($2,037). Seed was provided by John De Vlieger (Fava and Dundee varieties), Skagit Farmers Supply (Flex), and Albert Lea Seed (Admiral). Pre-planting and post-harvest soil data is available for those interested. Pre-mergent herbicides treflon (1 pint/acre) and dual magnum (1.5 pint/acre) were incorporated pre-planting. Fertilization was 18 lbs of nitrogen per acre and 60 lbs of phosphorus per acre at the time of planting. Production data are presented in Table 2; chemical analysis by variety is contained in Table 1.

Growing Season Observations and Comments

All seed varieties emerged and grew well. They thrived in the 2.9% organic matter, 6.8 pH soil with less than 3” of rainfall throughout the growth period. Chemical analysis content provided in Table 1 shows all pea varieties compared favorably with canola meal with respect to energy content, crude protein, and fiber digestibility.

Black aphids attacked the fava beans, but it was unknown if this affected productivity. The major challenge, however, was Canada geese: they moved through the fields in an orderly fashion from east to west, devouring all peas they encountered. Fortunately, data could be collected from the western side of each plot because these areas had not yet experienced any goose damage (Photo 2). Fava beans matured later than peas. The literature suggests pea production may be improved by planting a mixture of varieties; that was not done in this trial.


With their high protein content and positive environmental effects, peas are once again a crop worth considering for northwestern WA, this time as a locally-produced livestock feed. To increase the likelihood of success, growers will need to conduct soil tests and probably raise soil pH (peas do not perform well in acidic soils) and have a plan to mitigate effects of grazing geese. Additional studies of how grain peas could contribute to high-value crop disease control, soil quality, nutrient cycling, reduction of livestock feed costs, and a myriad of other factors would be excellent candidates for SARE on-farm research project funding.