Abstract
Relative variation (as expressed by the coefficient of variation) in yields or economic returns, in polycultures of annual crops versus sets of monocultures of the same species, was studied in theoretical models and in experimental polycultures grown near Ann Arbor, Michigan. The risk of obtaining disastrously low values was also discussed. Methods were developed for finding the combination of monoculture crops that should be least variable (minimum CV) in total value (combined yields), for comparison as an alternative to polycultures. A review of the statistical literature showed that the use of the median-Levene's test was both the most appropriate and the simplest test for significant differences in variation. Biological factors affecting stability in polycultures versus monocultures are discussed, including effects of crop pests, the area of l and devoted to each system, and competition between the polyculture crops. Models are used to explore potential effects of competition, with the conclusion that competition will tend to reduce stability in polycultures, relative to sets of monocultures, especially for each crop species considered by itself. Negative correlation between effects of environmental variation on the crop species is expected to reduce the relative stability of polycultures. In experimental polycultures of tomatoes (Lycopersicon esculentum) and cucumbers (Cucumis sativus) and of carrots (Daucus carota) and beans (Phaseolus vulgaris), each crop species was either significantly more variable when in a polyculture than as a monoculture; or there was no significant difference between cropping systems. No crops were significantly more variable as a monoculture. There were no consistent differences in variability in combined yields. Thus competition should tend to be a destabilizing factor in polycultures, although other effects which stabilize polycultures may occur. Advantages as well as disadvantages of variations are discussed. Finally, sociopolitical implications of technological solutions for reducing variation and risk are examined. Stability will tend to benefit smaller producers more than larger ones, but can also invite outside control or acquisition by large investors.
Abstract from the paper’s OpenAlex record, shown for indexing and research. Copyright remains with the authors or the publisher. Read at the source ↗
The text the model read, with the source record’s inline markup (italics, sub- and superscripts) rendered and its character entities decoded; quote offsets refer to the raw text.
Claims 9
Claim · model-written summary
Competition was modeled to reduce polyculture stability relative to monocultures, particularly for individual crops.
Verbatim
e0“competition will tend to reduce stability in polycultures, relative to sets of monocultures, especially for each crop species considered by itself”
t0“Annual Crops”
Claim · model-written summary
Negative correlation in environmental responses was expected to reduce relative polyculture stability.
Verbatim
e0“Negative correlation between effects of environmental variation on the crop species is expected to reduce the relative stability of polycultures”
t0“Annual Crops”
Claim · model-written summary
Tomatoes in polyculture were either more variable or did not differ significantly from monoculture.
- Taxon
- tomatoes
Solanum lycopersicume0 - Outcome
- variablee0
- Direction
- more variablee0
- Comparator
- monoculturee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“experimental polycultures of tomatoes (Lycopersicon esculentum) and cucumbers (Cucumis sativus) and of carrots (Daucus carota) and beans (Phaseolus vulgaris), each crop species was either significantly more variable when in a polyculture than as a monoculture; or there was no significant difference between cropping systems”
Claim · model-written summary
Cucumbers in polyculture were either more variable or did not differ significantly from monoculture.
- Taxon
- cucumbers
Cucumis sativuse0 - Outcome
- variablee0
- Direction
- more variablee0
- Comparator
- monoculturee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“experimental polycultures of tomatoes (Lycopersicon esculentum) and cucumbers (Cucumis sativus) and of carrots (Daucus carota) and beans (Phaseolus vulgaris), each crop species was either significantly more variable when in a polyculture than as a monoculture; or there was no significant difference between cropping systems”
Claim · model-written summary
Carrots in polyculture were either more variable or did not differ significantly from monoculture.
- Taxon
- carrots
Daucus carotae0 - Outcome
- variablee0
- Direction
- more variablee0
- Comparator
- monoculturee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“experimental polycultures of tomatoes (Lycopersicon esculentum) and cucumbers (Cucumis sativus) and of carrots (Daucus carota) and beans (Phaseolus vulgaris), each crop species was either significantly more variable when in a polyculture than as a monoculture; or there was no significant difference between cropping systems”
Claim · model-written summary
Beans in polyculture were either more variable or did not differ significantly from monoculture.
Verbatim
e0“experimental polycultures of tomatoes (Lycopersicon esculentum) and cucumbers (Cucumis sativus) and of carrots (Daucus carota) and beans (Phaseolus vulgaris), each crop species was either significantly more variable when in a polyculture than as a monoculture; or there was no significant difference between cropping systems”
Claim · model-written summary
No crop was significantly more variable in monoculture.
Verbatim
e0“No crops were significantly more variable as a monoculture”
t0“Annual Crops”
Claim · model-written summary
Combined yield variability did not consistently differ between cropping systems.
Verbatim
e0“There were no consistent differences in variability in combined yields”
t0“Annual Crops”
Claim · model-written summary
The authors concluded that competition tends to destabilize polycultures.
Verbatim
e0“competition should tend to be a destabilizing factor in polycultures”
t0“Annual Crops”