The impact of maize stand density on herbicide efficiency

Abstract

The impact of maize stand density (4, 8 and 12 plants per m 2 ) on herbicide efficiency (in %) and cob yield loss (in %) was studied in four field trials. The mixture of soil-applied herbicides (HS) isoxaflutole and S-metolachlor and the mixture of foliar-applied herbicides (HF) dicamba and rimsulfuron was applied in two dosages (100 and 75% of dose recommended by manufacturers). The 100% dose of HS was (75 g isoxaflutole + 960 ml S-metolachlor) per ha and 100% dose of HF was (12.5 g rimsulfuron + 240 ml dicamba) per ha. In all four trials, the studied factors (stand density, herbicide type and dose) had significant impact on herbicide efficiency and on maize cob yield loss. The herbicide efficiency decreased significantly, when herbicides were applied to maize of lower stand density and the maize yield losses increased. When weed population was composed predominantly of annual seed weeds higher efficiency was obtained by HS herbicides, conversely, when the weed population was composed predominantly of perennial weeds the HF herbicides provided better control. The reduction of herbicide dose always caused the significant reduction in herbicide efficiency and increase in maize yield loss.Keywords: maize; stand density; yield loss; herbicide efficiency; isoxaflutole; S-metolachlor; dicamba; rimsulfuron An enormous increase in public concern for the protection of the environment and increased awareness of pesticide residues in food and water, have necessitated a renewed appraisal of current crop production systems for all crops. In Slovenia maize is the most important field crop and the most problematic from an ecological point of view (herbicide residues in ground water). We are intensively studying the possibilities to reduce the herbicide use in maize production. In literature, many possibilities for reaching that goal are presented.The main possibilities from them are: use of lowered doses of herbicides (Mulder and Doll 1993, Rola et al. 1999), use of banded instead of broadcast application (Hamil and Zhang 1995, Heydel et al. 1999), banded application combined with between-row mowing (Donald et al. 2001), intensification of mechanical weed control methods combined with reduced doses Weide 1999, 2000), use of technology of living or dead mulch and cover crops (Ammon et al. 1995, Barberi 1997, weed flaming, use of mycoherbicides, patch spraying, changed seeding systems and mixed crops (Froud-Williams 1995, Ammon 1997).None of them are completely suitable for ecological and economical situations in all countries around the world. The use of lowered herbicide doses is the simplest way for reducing herbicide use without changing the production technology significantly. Slovenian farmers often search for information on methods for weed suppression with lowered herbicide doses. In literature, we can find interesting information on possibilities of drastic reduction of herbicide doses without causing the significant increase in maize yield losses. Most reports present cognitions that doses of herbicide can ...

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