Field pea seed residues: the potential for low cost weed control

Abstract

Plant growth suppression trials were undertaken with soil sampled 18 mo apart (2008, 2009) from two locations affected by field pea seed residues. Test plant species were grown in the residue-affected soil and compared to residue-unaffected soils, sampled from nearby fields. Germination was either fully inhibited or emergence delayed by more than one week in residue-affected soil. Dry matter accumulation of test species grown in residue-affected soil was significantly reduced compared to dry matter of these species grown in unaffected soil (P <0.0001). Canola and field pea were inhibited more than wheat and green foxtail over both years. Greenhouse trials also revealed that germination of wild oats was inhibited in the residue-affected soils, although overall, wheat and grassy weeds were less affected than dicots. Significant reductions of weed species diversity and abundance were correlated to residue-affected soils (P <0.0001) when compared to control soils using multi-response permutations procedures. In bioassays in sterile media, germination of wheat and canola seed was inhibited, using aqueous extracts of weathered pea seeds or extracts of the residue-affected soil. An allelopathic response was proposed to explain these results.