Corbin, A.T., K.D. Thelen, R.H. Leep, and G.P. Robertson
Presented at the All Scientist Poster Reception (2006-05-09 )
Weed management strategies for organic producers are generally limited to crop rotations, cover or companion crops, and mechanical cultivation. Experimental evidence suggests that longer crop rotations with diverse crops can reduce seedbank populations of important weed species in organic production systems. Prediction of weed seedling densities from buried seed reserves has been improved by considering specific sampling size, date, number and technique. For example, some investigators have found the greenhouse germination assay to be more reliable with a smaller sample size taken in early spring than seed extraction by elutriation when correlating field seedling densities. Germination techniques as predictive tools have been supported as more accurate methods of seedling density estimation. With a modified sampling technique designed to capture spatial variability by increasing number of soil cores of a reduced core diameter, others have shown enhanced predictability of weed seedling densities using a greenhouse germination assay. A four-year rotation of alfalfa, corn, soybean and wheat produced with organic sources of nutrients (manure and crop residue), and no synthetic chemical inputs may increase soil organic matter quality and decrease the weed seed bank as compared to one year of conventionally grown corn followed by three years of continuous alfalfa for the transition to a certified organic system. This hypothesis was tested throughout the 2005 growing season. Results of the greenhouse assay and field density estimations are incorporated into this poster presentation.
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