Goosegrass Seedling Emergence and Growth in Bermudagrass Canopy and Divots

Abstract

Goosegrass, Eleusine indica (L.) Gaertn., is a serious weed in bermudagrass, Cynodon spp. Rich., golf and sports turf. Reduction of canopy gaps such as divots might discourage goosegrass establishment because turf canopy reduces sunlight that could stimulate goosegrass seed germination. The objective was to compare goosegrass seedling emergence and growth under different conditions of bermudagrass canopy, including bare soil and divots of different ages, and the effect of fertilization rates. The first experiment compared surface treatments. Goosegrass seeds were planted monthly for 12 months in bare soil and divoted pots in a glasshouse. Initial goosegrass seedling emergence was large in the first month after planting, 23% in divots and 20% in bare soil, compared with only 9% emergence from canopy. Reduced emergence occurred from 2 to 8 months in canopy, divots, and bare soil. Cumulative goosegrass emergence was 44% in divots, 40% in bare soil, and 31% in canopy. In a second experiment, goosegrass seeds were planted in divots 0, 2, 4, 6, 8, and 10 weeks old. Divots were visibly closed within 4 to 6 weeks. By 9 weeks after seed planting, goosegrass seedling emergence was reduced 72% after planting in 10-week-old divots compared with fresh, 0-week divots. Goosegrass continued to emerge through all 63 weeks observed after seed planting. High fertilization rate, 123 g N/m2/year, from 10 to 63 weeks reduced cumulative late seedling emergence 34%, compared with half-rate fertilization, probably due to denser canopy under high fertilization. In a third experiment, goosegrass seedlings planted in closed bermudagrass canopy grew 90% less, in root and shoot fresh and dry mass, compared with seedlings planted in divots. Across all experiments, goosegrass emergence and growth were reduced by increased canopy.