Productivity of FieldPea (Pisumsativum L.) and Spring Oat (Avena sativa L.) Grown as Sole and Intercrops Under Different Nitrogen Levels

Intercropping cereal grains and legumes has potential as an alternative cool-season forage cropin low-input farming systems. The objectives of this study were to quantify the effects of density, species proportion and nitrogen (N) supply on the biomass accumulation of field pea and spring oat grown as sole or intercrops. Greenhouse experiments were conducted using an additive series experimental design. Treatments included threefertilizer Nrates and 20 density/proportion combinationsin a randomized complete block with four replications. Sole plant densities included 2, 3, 4, 5 plants of each species pot-1 (16 cm in diameter, 16 cm in height). The species ratios per pot for the intercrop included 1-1, 1-2, 1-3, 1-4, 2-2, 2-3, and 3-5 and their reciprocals. Nitrogentreatments included urea at 0, 0.2, or 1.0 g N pot-1in a split application. Plants were harvested and oven dried to constant weight at 46 days after planting. As density increased, sole cropped oat and fieldpea biomass increased. In the intercrop, oat showed greater biomass accumulation at higher N levels, whereas field pea biomass was reduced at the highest N level. In both sole and intercrop, oat was more sensitive to intraspecific competition than field pea. Niche differentiation was only observed at the highest N level. At higher N and lower total density, mixtures yielded more than monocultures, indicating that intercropping of field pea and spring oat may be beneficial. Results from this study can aid in future field research to determine optimum density for each species and N rates to be applied in field pea-oat intercropping systems.