... Antonovics and Levin ( 198 0), Weiner ( 198 2),Goldberg and Werner ( 198 3), Barkham and Hance ( 198 2), Pacala and Silander( 198 5), Silvertown et al. ( 199 2), and Wallinga ( 199 5). Although a distinctionRN0,tᎏᎏᎏᎏ[1 ... (Ampong-Nyarko and de Datta, 199 3;Barbour and Bridges, 199 5; Holt, 199 5), water stress (Paterson, 199 5), fertil-ization strategies (Ampong-Nyarko and De Datta, 199 3; di Tomaso, 199 5), and tillage ... (Müller-Schärer and Frantzen, 199 6; Swanton and Murphy, 199 6). The problem, as a number of researchers(Cousens and Mortimer, 199 5; Swanton and Murphy, 199 6; Jordan and Jannink, 199 7) have pointed...