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Weed Ecology and Management Learning Module
Weeds substantially constrain production on most organic farms in the northeastern U.S.A. Recent intensive study of eleven northeastern organic farms indicated that 25% of crops probably suffered some yield loss from weeds, and weeds interfered with harvest in some additional crops even though yield probably did not suffer. Even when weeds are controlled, weed management often represents a significant labor expense on organic farms. Moreover, fear of weeds escaping control appears to be a major factor inhibiting conventional farmers from adopting organic practices.
Since weeds are such an important pest problem in organic systems, much of the work for the project revolves around weeds and weed management. Regular sampling of weeds in the treatments will include samples of the density of buried seeds in the soil (the soil seed bank) each spring. The density of seeds in the seed bank indicates likely weed pressure in the crops and also provides an average measure of the effectiveness of weed management practices over time. (Here's how we measure weed seeds in the soil.)
To assess the actual weed pressure we will estimate the dry weight (biomass) of weeds in the mature crops by clipping them at soil level and weighing the weeds in four 0.5 m2 quadrats in each plot. A quadrat is just a frame of a given size that we place on the ground to count, measure or clip weeds in a known area. One of the main goals of the study will be to assess the effectiveness of various cultivation practices. We will do this by counting weeds in quadrats before and after cultivation events. For tine weeding, which is largely aimed at killing weeds that have germinated but not yet emerged (weeds in the "white thread" stage), we will do counts in the tine weeded main plots and in subplots that are protected from tine weeding by a board fastened to the soil with stakes.
Some specific questions that we are hoping to answer include:
Click on any of the questions above to learn more.
When you are done with the module, take the self test to see what you have learned.
© Copyright, Department of Horticulture, Cornell University.
Logo graphics by Rachel Kennedy.
Design by Craig Cramer.
Mention of trade names and commercial products is for educational purposes; no discrimination is intended and no endorsement by Cornell Cooperative Extension or Cornell University is implied. Pesticide recommendations are for informational purposes only and manufacturers' recommendations change. Read the manufacturers' instructions carefully before use. Cornell Cooperative Extension and Cornell University assumes no responsibility for the use of any pesticide or chemicals. Some of the links provided are not maintained by Cornell Cooperative Extension and Cornell University. Cornell Cooperative Extension and Cornell University are not responsible for information on these websites. They are included for information purposes only and no endorsement by Cornell Cooperative Extension or Cornell University is implied. Cornell Cooperative Extension provides equal program and employment opportunities.
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