Interference of three annual grasses with grain sorghum (Sorghum bicolor).
Barnyardgrass (Echinochloa crus-galli), large crabgrass (Digitaria sanguinalis) and Texas panicum (Panicum texanum) were evaluated in field experiments over 3 years to measure their duration of interference and density on grain sorghum cv. Acco 4012R and Funk G-623 GBR yields. When grain yield data were converted to a percentage of the weed-free control, linear regression predicted a 3.6% yield loss for each week of weed interference regardless of year or grass species. Grain sorghum grown in a narrow (61-cm) row spacing was affected little by full-season interference; however, in wide (91-cm) rows, interference increased as grass density increased. Data from the wide-row spacing were described by linear regression following conversion of grain yield to percentages and weed density to log10. A separate nonlinear model also was derived which could predict the effect of weed density on grain sorghum yield.