The Implications of Improving the Conservation Value of Field Margins on Crop Production.

Abstract

The effect of field margin management on crop yield and weed biomass in the crop edge (headland) was investigated. Treatment did not have any significant effect on cereal yields, and taking a one metre strip out of crop production to establish a sterile, natural regeneration or sown strip, did not significantly reduce yields compared to cropping to the field edge. Conservation headlands generally contained greater amounts of weed biomass than fully sprayed headlands, but grain yields were not significantly reduced. Soil compaction affected yield in one of the field experiments, but not the other, where soil density values were fairly uniform. No relationship was found between fertiliser application and yield.
In a survey of cereal headlands, distance from the field boundary was the most important factor affecting yield. Where yield increased with distance from the field boundary, there was a strong linear relationship with log distance (P<0.001). Weed dry matter was related to distance, and there was a significant relationship between weed dry matter and grain yield in the first year of the survey (P<0.001), but not in the second.
Communities of herbaceous field margin species were established, and the effects of nitrogen fertiliser and sublethal glyphosate application were examined over two years. Cover abundance of grasses was greater than that of dicotyledonous species throughout. Bromus sterilis was the most abundant species in 1995, but by 1996 it had been replaced by Arrhenatherum elatius. Increasing fertiliser rate had a negative effect on total vegetation cover in 1995, due to individual plants lodging. During 1996, fertiliser application increased the cover abundance of the dominant perennial species A. elatius (P<0.001), and also the annuals B. sterilis and Galium aparine (P<0.05). Sublethal doses of glyphosate significantly reduced total cover abundance (P<0.001), and had a greater effect on grasses compared to dicotyledonous species.
Measurement of spray drift into a hedgerow showed that positioning the end of the tractor-mounted spray boom 2m or 6m away from the crop edge reduced drift into the hedge-bottom compared with spraying up to the crop edge (P<0.001).