Plot and border effects on herbicide-resistant weed seed consumption by rodents in corn and soybean crops of central Argentina

Abstract

Biological control of weeds is a key ecological function of agriculture production. Our aim was to determine howborder quality, distance to border, crop type and phenology, affect the consumption of herbicide-resistant weedseeds by rodents in the agroecosystems of central Argentina. We used seeds of four commonly problematic weedsand two crops in a consumption experiment with three exclusion treatments. We studied seed consumption atthree distances of the border in 20 crop plots (10 soybean and 10 maize) associated with borders of differentquality in spring and summer. We measured nine environmental variables and determined the abundance ofrodents for each site. Seed consumption varied greatly among seed species, Amaranthus hybridus and Zea mayshad the highest mean consumption rate, followed by Sorghum halepense and Digitaria sp., Ipomoea purpurea andGlycine max were rarely consumed. Our model predictions show seed consumption rates above 20 % for Digitariasp, and 40 % for A. hybridus with the increase of border vegetation volume. On the other hand, Z. mays consumption reaches more than 30 % in summer. This high weed seed consumption would modify the populationand community dynamic of the weeds by impeding seed entrance to the seed bank. Our results highlight thatrodents could perform biological control of herbicide-resistant weeds. The positive effect that habitats with highvegetation cover have on rodent species suggests that appropriate management strategies like maintaining highquality field borders and establishing natural and semi-natural patches can enhance weed biological control inindustrialised agroecosystems.