Suppression of Annual Weeds in Pea and Cereal Intercrops

Experiments were constructed to investigate e effects of pea [Pisum sativum L. (Partim)] and spring cereal intercrops on annual weed suppression and grain yield in an organic farming system. Pea, spring wheat (Triticum aestivum L. emend. Fiori et Paol.), barley (Hordeum vulgare L.), oat (Avena sativa L.), and triticale (x Triticosecale Wittm.) were sown as sole crops and as intercrops at a 50: 50 proportion of grain legume and spring cereal seeds relative to sole crop rates. The density of wheat, oat, and triticale sole crops was significantly higher compared with intercrops with pea. All investigated intercrops were significantly denser than the sole pea crop. Low height was observed in pea and barley sole crops and intercrops. Mostly weed number and mass were not significantly different between sole cereal and intercrops. Crop density was more effected by suppression than weed height. Where crops were sparser, increases in weed density and mass corresponded to a significant decline in grain yield. In the peacereal intercrop, where pea accounted for 20.3 to 35.2% of the total plant number, cereals exhibited the greatest weed suppression ability, productive stem number and height being the main factors responsible for this.