Field peas are an emerging alternative crop for producers in northern Kansas. Field peas are a pulse crop, a cool season grain legume. Currently in northern Kansas, field peas range in growth stage from just germinating to having several above-ground nodes present, depending on planting date and field conditions. Field peas will germinate at soil temperatures of 40° F. Depending on conditions, emergence may take from 10-14 days. A unique feature of field peas, compared to other broadleaf crops typical to Kansas (soybean, cotton, sunflower), is a hypogeal emergence. In other words, the cotyledons remain below the soil surface. This type of emergence provides a higher level of tolerance to freeze events.
Field pea seedlings are generally tolerant to spring frosts into the mid 20’s and can survive even lower temperatures if under snow cover (Table 1).
Table 1. Percentage seedling survival for 10 legume species at four seedling ages* and temperatures. Meyer and Badaruddin, 2001. Crop Sci. 41:1838-1842.
In the event that above-ground biomass is damaged by freezing temperatures, field peas have the ability to regrow from the auxiliary or scale buds that are located below the soil surface (Figure 1).
Figure 1. Field pea growth stages. Figure by K. McKay, North Dakota State Univ.
If plants are at or beyond the 7th node stage when freeze occurs, plants are not likely to survive as auxiliary bud initiation will not occur. The ability for regrowth from the auxiliary buds results in relatively minor yield losses in cooler climates. In Kansas, heat stress at flowering and pod fill is the key yield limiting factor. Regrowth from auxiliary buds will be delayed in development and will likely be entering into these critical growth stages at higher temperatures, thus reducing yield potential. Expect significant yield losses in fields that become reliant on regrowth following a freeze event.
If producers have field peas that are injured by frost, they are encouraged to contact Lucas Haag, Northwest Area Agronomist, so that together we can learn more about how peas respond to frost events in the Central Plains.
Lucas Haag, Northwest Area Agronomist, Northwest-Research Extension Center, Colby