Natural Vegetation and its Influence on Weed Populations in Neighboring Fields

View the project final report

• 2003 annual report

Commodities

• Agronomic: corn, peanuts

Practices

• Crop Production: windbreaks
• Farm Business Management: whole farm planning
• Natural Resources/Environment: biodiversity, habitat enhancement, hedgerows, wildlife, hedges - woody
• Pest Management: weed ecology
• Production Systems: agroecosystems

Natural vegetation on farms provide increased biodiversity, structural diversity,
habitat for wildlife and beneficial insects, and can act as protective buffers against
agrochemical drift. Nevertheless, farmers frequently view these areas as potential sources
of weeds, insect pests, and diseases. Objectives of this study were to examine weed
species richness and abundance in cropland bordered by managed versus unmanaged
field margins to determine if differences in weed infestation exist. Weed abundance and
richness were measured in crop fields along permanent transects that extended from the
field edge to the center of the crop fields. Presence/absence data for all plant species in
the field margin were also recorded.

Transect data from fields with margins of natural vegetation were compared to
transect data from fields with managed margins using analysis of variance. There were
no differences between log total abundance of weeds in crop edges adjacent to managed
and unmanaged field margins (P=0.44). For both margin types, more weeds were found
near the field edge than in the center of the field (1.37±0.08 to 0.52±0.07 and 1.39±0.07
to 0.41±0.06, for managed and unmanaged field margins respectively). Species richness
was slightly higher along crop edges of managed field margins (7.35±0.32) than crop
edges along unmanaged field margins (6.55±0.31). Managed field margins had lower species richness than unmanaged field margins – less than half the mean number of species (5.8±0.28 versus 14.7±0.62 species, respectively).

No association was found between plant species occurring in the field margin and
in the crop field by generating 2 x 2 contingency tables via PROC FREQ and testing the
association with Fisher’s exact two-sided test. Using logistic regression via PROC
GENMOD, margin type and weed presence in the field margin were not effective
predictors of weed occurrence in the crop field.

Introduction

Natural vegetation on farms such as field margins, fallow fields and wooded areas provide increased biodiversity, structural diversity, habitat for wildlife and beneficial insects, and can act as protective buffers against agrochemical drift (Kleijn 1997). Nevertheless, farmers frequently view these areas as potential sources of weeds, pests, and diseases. The relationship between managed and unmanaged field margins and adjacent cropland was examined relative to diversity, abundance, and distribution of weedy species.

• to determine if crop edges adjacent to unmanaged field margins are associated with higher weed species richness and abundance than crop edges bordering managed areas

  to determine how weedy species are distributed in the field with respect to distance from the field edge

  to assess the presence of weedy species in the field margins and boundary areas and to determine if there is an association between weeds occurring in the field margin and the presence of the same species in the crop field