Sugarcane Response to Bermudagrass Interference

The competitiveness of three phenotypically different sugarcane cultivars with bermudagrass was determined in field trials. In trial one, bermudagrass biomass was 22% less in CP 70-321 than in HoCP 85-845 in the plant-cane crop, but biomass was 130 to 170% greater in CP 70-321 than in the other two cultivars during the second-ratoon crop. CP 70-321 emerges quickly following planting, which might have reduced bermudagrass growth in the plant-cane crop, but the lower stalk population of CP 70-321 might have promoted bermudagrass survival and growth during the second-ratoon crop. In trial two, there were no differences in bermudagrass biomass when comparing its establishment in the different cultivars. Sugarcane, averaged across cultivar, produced fewer stalks and was shorter when competing with bermudagrass. In the plant-cane crop, stalk populations were reduced 13 to 23%. In the first-ratoon crop, stalk population was reduced 8 to 15%. In the second-ratoon crop, stalk population was reduced 8 to 10%. Bermudagrass interference reduced sugar yields by 8 to 32% in the plant-cane crop, with reductions of no more than 9% in the first- and second-ratoon crops. The greater yield loss in the plant-cane crop in the first production year shows the importance of controlling bermudagrass in the summer fallow period prior to planting and during establishment of the plant-cane crop. Nomenclature: Bermudagrass, Cynodon dactylon L. Pers. CYNDA; sugarcane, Saccharum interspecific hybrids ‘CP 70321’, ‘LCP 85-384’, ‘HoCP 85-845’. Bermudagrass is a troublesome perennial weed problem for Louisiana sugarcane growers. Sugarcane in Louisiana is planted vegetatively (using stalk pieces) in late summer or early autumn and is cultivated as a perennial crop lasting 3 to 4 yr. During this 3- to 4-yr cropping period, tillage is limited to the row sides and bottoms, and once perennial weeds such as bermudagrass become established, they are difficult to control. Following the final production year, sugarcane fields are generally deeply tilled using a disk plow to destroy sugarcane plants after which fields are generally left fallow or occasionally are planted with a spring-seeded crop such as soybean [Glycine max (L.) Merr.] until they are replanted with sugarcane. This fallow or rotational period is the optimal time for controlling bermudagrass in sugarcane fields through combinations of tillage and herbicide applications (Richard 1997). When bermudagrass is not sufficiently controlled during the fallow period or when sugarcane is replanted immediately following harvest (succession planted), bermudagrass can easily re-establish from viable rhizome and stolon pieces