Emergence of weeds as affected by vertical seed distribution in arable soils

Abstract

A glasshouse study examined weed seedling emergence in soils collected from 20 sites Soil was placed in open topped columns of differing heights and the number of seedlings that emerged were counted A total of 77 different weed species emerged but most were in small numbers Four summer broadleaf weeds black nightshade (Solanum nigrum) fathen (Chenopodium album) spurrey (Spergula arvensis) and willow weed (Polygonum persicaria) showed little restriction and emerged freely from depths up to 50 mm Of the grasses summer grass (Digitaria sanguinalis) and annual poa (Poa annua) were clearly constrained at depths greater than 20 mm while smooth witchgrass (Panicum dichotomiflorum) was not Of the other broadleaf weeds waxweed (Hydrocotyle sp) and Lotus sp were constrained at depths greater than 30 mm while two smallseeded species cudweed (Gnaphalium sp) and toad rush (Juncus bufonius) did not emerge from depths greater than10 mm