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Project description

Precision Agriculture: Comparison of Weed Seed and Previous Weed Populations for Prediction of Subsequent Weed Populations. (97DS031)
Program UC IPM competitive research grants program
W.T. Lanini, Vegetable Crops, UC Davis
Host/habitat Unspecified
Pest Unspecified Weeds
Discipline Weed Science
Decision Support
Start year (duration)  1997 (Two Years)
Objectives Evaluate two sampling methods, weed seedbank (Elutriation-Germination method) and weed population sampling the previous growing season, alone or in combination, for predicting summer weed populations and their distribution within a field.

Analyze the weed populations at crop harvest and weed seedbanks during the winter, in terms of the species composition and spatial distribution, and determine the most reasonable sample size to describe such populations at a farmer's level of resolution.

Most herbicides are applied uniformly throughout a field, prior to weed emergence, yet it is known that weed distribution is not homogeneous. If weed species and location were known, appropriate treatments could be applied at each location. Some portions of the field could receive lower rates (soil texture change or more sensitive weed species) or no herbicide (few weeds or species not controlled by labeled herbicides). This study is examining methods for predicting weed species, density and distribution within a field, in order to apply preemergence herbicides precisely where they are needed. In year one, it was determined that weed seedbanks were better at predicting weed species and location than previous years' escaping weeds. Correlation coefficients between seeds and seedlings, although significant for many species, were low. Evaluations of ways to improve sampling efficiency again found that germinating weeds in the greenhouse for one flush was as reliable as three or four flushes, which could reduce the time needed for this step. Seedling emergence in the field was less than 20% of the estimated seedbank. Weeds were found to be clumped in the field, rather than evenly distributed. Weed populations at crop harvest in 1997 were less reliable in explaining weed seedlings in 1998, than were soil seedbank measurements. This is similar to what was observed in 1997. Although weed sampling at crop harvest has been less accurate at predicting next year's weeds, sampling intensity at crop harvest was increased in 1998 in hopes of improving prediction accuracy, as this type of sampling is much less time consuming and costly than soil sampling.

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