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New ecology proposal

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Elizabeth Yin

on 21 April 2010

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Transcript of New ecology proposal

Assessing the Resource-Pool Diversity Hypothesis:
Does the presence of a diverse resource pool decrease the competitive interactions between a target crop and invasive weeds? Elizabeth Yin April 20, 2010
Agriculture What's wrong? Solutions? Use ecology to:
increase crop yields
combat pests
reduce invasives artificial selection- decreased fitness
increased reliance on petroleum products
weeds, pests, diseases
monocultures Current Techniques Intercropping Crop Rotation alters composition spatially and temporally
reduces biomass and density of weeds prevents soil degradation
increases crop yield
reduces weed densities crops grown simultaneously
increases yield
decreases weed populations
past studies only investigate specific mixtures Mechanisms Ecological mechanisms could explain weed responses to crop rotation and intercropping Allelopathic Interference Resource Competition niche-based differentiaton
target crops, intercrops, weeds may use resources differently
success determined by availability of resources
tradeoffs - Tilman (1985) Resource Ratio Hypothesis maximum number of concurrent species = number of limiting resources
suggests that multiple crops would be in competition for single resource
How can we reduce competition between intercropped species?
Resource-Pool Diversity Hypothesis Access to different resource pools should reduce the intensity of competition between species and increase crop yield Diverse soil resource pool... diverse crop and cover crop rotations
different fertility sources- animal/green manure, compost
residues from plants and weeds
provides heterogeneous soil environment should reduce competitive interaction in an invasive environment
crops and weeds can acquire nutrients from different resource pools Validity Smith et al (2009) Experiment examining interaction between crops and weeds in conventional vs. organic farming
resource pool diversity (2-5) vs (5-9)
organic crop yield not or minimally reduced (0-18%)
weed abundance increased 29-2000% Crop yield-weed abundance may differ between systems based on potential RPD Currently, no direct test of RPDH This study will test the validity of the resource pool diversity hypothesis manipulation of the resource-pool diversity
diversity of intercropped plant species
presence of invasive species Hypothesis RPDH will be upheld

plants grown under conditions of high resource-pool diversity will have higher yields

increased availability of resources will decrease competition between crops and invasives

inclusion of intercropped species will increase diversity of soil-resource pool Methods Study System Target crop: Maize
Intercrop: Soybeans randomized split-block design Plot 1 Plot 2 Plot 3 All plots will receive all possible combination of resources
no fertilizer
green manure (clover, undertilled yr 0)
standard nitrogen fertilizer 0.5 m 0.5 m 1.0 m 1.0 m Natural weed populations will persist
will be added if absent in field Results Harvest assessed for biomass and yield relative to control Invasives assessed for diversity, density, and biomass RPDH upheld

Increase in nutrient sources will lead to increase in yield of maize

weed biomass may also increase, little effect on crop yield

Intercropping results weed density should decrease in plots with intercropping and fertilization
yield of maize decrease by intercrops @ low nutrient diversity
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