Spatial Relations of Weed Management Practices and Agroecologically Dominant Weed Species with Organic Dairy Farms in Southwestern Wisconsin

Conservation of biodiversity in organic agriculture has spurred much debate over the role of organic systems in the environment. However, little is known about the relationship between the variations in weed management practices and the biodiversity of weedy species in organic agriculture. Specifically, how does the spatial distribution and diversity of weedy species vary in relation to diversity in weed management practices? Species identification, vegetative samples, and farmer interviews took place on 20 farms in southwestern Wisconsin to explore how the landscape structures spatial variation in weedy species and how weed management practices respond accordingly. Southwestern Wisconsin, known as the driftless region, is an area of unglaciated hilly terrain with a high density of organic farms. Because of the area’s topography and landscaped diversity I hypothesize that weedy species would be spatially distributed according to environmental characteristics (e.g. soil type and moisture), as well as land uses (e.g. pasture vs. crop fields). This study finds weed species distribution to be independent of environmental variables, but significantly correlated with field type (pasture vs. corn). This difference may be inherent to the ecology of each field, but more significantly indicates the importance of management. Further research on current weed management techniques and distribution of weedy species on organic farms will enable researchers, extension agents, certifiers, and others to better facilitate the transition to organic agriculture. Successful transitions are paramount in light of continued growth of the organic sector in the U.S. and would not only help farmers produce higher yields (and therefore be economically viable), but also uphold the environmental and social-ecological goals of the organic movement.

STUDY AREA

Data Information National Elevation Dataset - Wisconsin 10m (2009) Elevation, slope SSURGO 2.2 (2005) % sand, silt, clay, pH, organic matter Palmer Drought Severity Index - NOAA Climate Prediction Center Wisconsin PDSI divisions

SAND SILT CLAY OM PH ELEV MIN_S MAX_S MEAN_S

min 7.00 41.00 14.00 2.00 6.00 266.78 0.01 13.33 2.84

mean 12.80 63.59 21.02 2.48 6.12 364.30 0.10 55.20 11.79

max 27.00 71.00 31.00 5.00 7.00 411.07 0.36 128.06 20.42

std 5.60 9.12 3.91 0.66 0.24 30.51 0.06 27.90 4.54

QUESTION: “What is the relationship between variations in weed management and biodiversity of weeds?”

HYPOTHESIS: Weedy species will be spatially distributed according to environmental characteristics (e.g. soil type and

moisture), as well as land uses (e.g. pasture vs. crop fields).

•  PC-ORD (McCune & Mefford 2006) •  Two-way cluster analyses •  Bray-Curtis ordinations •  Joint plot overlays

RESULTS cont.

Environmental Data collected for all farm sites:

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# Cultivations

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Field data collected for all farm sites:

•  Vegetative identification, collection, and sampling of field weeds were conducted on 20 farms – 18 were USDA certified organic, 2 were not. I conducted vegetative sampling in pasture and cornfields only. •  Interview questions were focused on three aspects of weeds and weed management on dairy farms: (1) farmer perception of weed diversity, (2) farmer perception of weed abundance, and (3) weed management.

Anna M. Shamey, The Pennsylvania State University, State College, PA, 16801

METHODS & ANALYSIS

•  Greater than average precipitation early in the growing season, combined with higher than normal temperatures later in the growing season led to increased plant growth, while inhibiting typical cultivation cycles.

In a typical season, farmers cultivate 4-5 times over several weeks. Constant rains throughout the month of June greatly inhibited this.

•  Lack of alternate weed management suggested a static weed management system. This can be compared to dynamic management systems as exemplified by the milpa shifting cultivation system in Mexico (Berkes et al. 2000).

Static vs. Dynamic Management Systems

‘Decision tree’ exemplary of milpa shifting cultivation system

Typical (above) and example ‘alternate’ (below) weed management systems for study area farms

RESULTS

•  Weed species distribution was highly correlated with field type (pasture vs. corn). •  Cornfields were largely dominated by broadleaves. •  Pastures contained more even mixtures of broadleaves, grasses, and legumes.

CONCLUSIONS

•  Minor weed species variation did not appear to matter as weeds were managed categorically, as in plant functional groups. Functional groups appeared to refer to plant life cycles (annual, biennial, and perennial) as well as overall plant structure (e.g. broadleaves and grasses). •  Farmers prefer to get information regarding weed management from other farmers - this may explain the widespread usage of an inflexible yet successful weed management system. •  Transitions from conventional to organic may be better envisioned as a two-phase process (one short-term and one long-term) to enable farmers to remain open to trying new management techniques and to continue experimenting after being certified.

McCune, B. and M.J. Mefford. 2006. PC-ORD. Multivariate Analysis of Ecological Data. Version 5. MjM Software, Gleneden Beach, Oregon, U.S.A.

Berkes, F., J. Colding, and C. Folke. 2000. Rediscovery of traditional ecological knowledge as adaptive management. Ecological Applications 10(5): 1251-1262.