Competitive response of maize against glyphosate-resistant Digitaria insularis and Eleusine indica

To optimize integrated weed management, it is essential to understand the competitive ability of maize hybrids with new traits when coexisting with the weed community. Thus, the aim of this study was to evaluate the competitive ability of the maize against E. indica and D. insularis weeds under greenhouse (controlled conditions) and in the field by additive and replacement series designs, with different densities for each condition. 

In greenhouse experiments, maize coexisting with E. indica resulted in negative relative growth for leaf area and shoot dry mass, indicating damage to both species. However, maize with D. insularis did not exhibit negative relative growth, suggesting a different interaction. The analysis of relative competitiveness and aggressiveness revealed significant values for maize with D. insularis, indicating a competitive relationship. In contrast, maize with E. indica showed non-significant values, suggesting a less competitive interaction. In field experiments, the full model and reduced models showed good fit to the data, with non-significant differences between them, indicating that the interference of these weed species on maize yield were similar. 

The Principal Component Analysis identified four principal components. For PCs 1 and 2, chlorophyll-related variables exhibited a high relative contribution, showing a positive correlation with cases involving high density of D. insularis. Variables related to ear insertion height, plant height, stem diameter, and stand of plants had greater relative importance for PC 1, especially for cases with higher density of E. indica. This highlights the resilience of maize to competitive conditions and suggests that its capacity for rapid growth in height makes this crop effective in competition for light, even against other C4 species.

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