Agro‐ecology of onion couch ( Arrhenathemm elatius var. bulbosum).

SUMMARY The agro‐ecology of onion couch ( Arrhenatherum elatius var. bulbosum), a well known weed of arable land is studied. Contribution of seeds from onion couch and a more widespread variety of Arrhenatherum elatius : tall oat‐grass, towards future ingress of onion couch in arable fields has indicated that the tall oat‐grass variety is not a potential weed of arable land. It appears that vegetative propagules rather than the seeds are the effective means of propagation of the onion couch variety in arable fields. An experiment performed to test any modifying effect of the soil texture indicated that onion couch is restricted to loamy soils and there is a complete absence from heavy clays and sandy soils. This could be due to the moist and protective micro‐environment provided by the texture of the soils to partially buried vegetative propagules of onion couch, which are susceptible to drought.