Intercropping of oat and field pea in Alaska: An alternative approach to quality forage production and weed control

Intercropping of legumes with non-legumes is an ancient crop production method used to improve quality and dry matter (DM) yields of forage and grain, and to control weeds. However, there is little information regarding intercropping at high latitudes. The objectives of this field study were to evaluate performance of (1) sole cropped oat (Avena sativa L.) (cultivars Toral and Calibre) and pea (Pisum sativum L.) (cultivars Carneval and Orb) and their intercrop combinations, and (2) inter- and sole-crop responses to weeds. The different cropping systems were studied with different weed treatments (weed-free all season long, weed-free until flowering, and left weedy all season long). In general intercrops of oat and pea produced DM (forage) and grain yields similar to sole oat crops and higher than sole pea crops although the difference was not statistically significant. Furthermore, forage quality [crude protein (CP), acid detergent fiber (ADF) and neutral detergent fiber (NDF)] was improved by intercropping. Most of the variables measured were unaffected by weed treatments, however weed DM was generally lower in sole oat and oat-pea intercropping than sole pea cropping systems. More than 80% of the weed DM was from common lamb's quarters (Chenopodium album L.). The CP of this weed was higher than oat and pea, and ADF and NDF were equivalent to the sole cropped oat. Thus, including weeds as part of the forage is possible. However, if crops are grown for grain, weeds are likely to produce large numbers of seeds that would enter the seed bank. Thus, pea–oat intercrops show potential as an alternative and sustainable approach for optimum yield and high quality forage and weed control under Alaskan subarctic conditions.