The influence of nitrogen supply on the ability of wheat and potato to suppressStellaria mediagrowth and reproduction

Abstract

SummaryThis paper tests the hypothesis that increased soil nitrogen supply reduces the growth of late‐emerging weeds in wheat and potato by enhancing canopy leaf area development and thereby reducing the availability of light for weed growth. Two series of experiments were conducted: one in spring wheat (1997, 1999) with sownStellaria mediaand one in potato (1998, 1999) with naturally emerged weeds, includingS. media. For each crop, two cultivars were grown at three levels of nitrogen supply. In wheat, as in a monoculture ofS. media, total dry weight and seed number of the weed increased with soil nitrogen supply, whereas in potato the opposite was found. Increased soil nitrogen supply increased the nitrogen uptake ofS. mediain wheat, despite the reduced light availability, indicating thatS. mediain wheat was limited by nitrogen. In potato, on the other hand, growth ofS. mediawas limited by light availability, which decreased with increased soil nitrogen supply.We conclude that the differences in response ofS. mediain wheat and potato to additional nitrogen supply are attributable to the dual influence of soil nitrogen supply on light and nitrogen availability, which are mediated by the crops.