Effects of Density, Species Ratio and Nitrogen Supply On Biomass Accumulation of Spring Oats and Field Peas in Sole and Intercropping.

Intercropping cereal grains and legumes has potential as an alternative cool-season forage crop in low-input farming systems. The objectives of this study were to quantify the effects of density, species ratio and nitrogen supply on the biomass accumulation of field pea (Pisum sativum L.) and spring oat (Avena sativa L.) grown as sole or intercrops. Greenhouse experiments were conducted using an additive series experimental design. Treatments included 3 N fertilizer rates and 20 density/proportion combinations in a randomized complete block with four replications. Sole plant densities included 2, 3, 4, 5 plants of each species pot^-1. 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. Nitrogen treatments included urea at 0 g, 0.2 g or 1.0 g N in a split application. Plants were harvested and oven dried to constant weight at 46 days after planting. As density increased, sole cropped oat and field pea 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 levels and lower densities, some 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 research to determine optimum density for each species in field pea-oat intercropping systems.