Goosegrass and Bermudagrass competition under compaction
Goosegrass (Eleusine indica L.) is a serious weed in trafficked areas of bermudagrass (Cynodon spp.) golf and sports turf. The objective of this study was to evaluate soil compaction and canopy cover as determinants of goosegrass competition in bermudagrass turf in sand soil. Goosegrass cover, plant density, and soil penetration resistance (SPR) were measured in traffic and no-traffic plots in bermudagrass golf course tees and sports field foul areas. Goosegrass plant density and cover were larger in traffic plots compared with no-traffic plots. Soil penetration resistance increased only at 5.0 cm depth due to traffic, while other soil properties including bulk density measured in golf course tees showed no effect from traffic. Two experiments measured the effect of controlled soil compaction on root and shoot dry weight of goosegrass and bermudagrass in containers. The first experiment evaluated effects of three soil compaction levels (1.14, 1.24, 1.33 g cm–3 bulk density) on goosegrass and bermudagrass grown separately. The second experiment evaluated effects on the two species grown together in competition, from two soil compaction levels (1.07 and 1.26 g cm–3 bulk density), two N application rates (48 and 96 kg ha–1 mo–1), and two mowing heights (1.3 and 2.5 cm). The second experiment also evaluated goosegrass seedling emergence and tiller numbers. When species were grown separately, bermudagrass root and shoot dry weight showed no effect from soil compaction, but goosegrass root weight was reduced. When species were grown together, bermudagrass root weight was reduced by compaction, but goosegrass was not affected. Goosegrass seedling emergence was reduced 58% by high mowing height, which paralleled an increase in bermudagrass canopy cover based on shoot dry weight. Canopy cover, not compaction, more readily explained the competition and infestation of goosegrass in trafficked areas in sand soil.