Submitted to: Washington State University College of Agriculture and Home Economics
Publication Type: Experiment Station
Publication Acceptance Date: 6/1/2014
Publication Date: N/A
Citation: Interpretive Summary:
Technical Abstract: The residue characteristics and decomposition of spring and winter canola (Brassica napus L.) cultivars currently grown in the Pacific Northwest (PNW) was investigated. Above- and below-ground residue was collected post-harvest in 2011 and 2012 from Univ. of Idaho Canola Winter Variety Trials at Odessa, WA (irrigated site), Moscow and Genesee, ID, and Spring Variety Trials at Davenport and Colfax, WA and Moscow, ID. Residue was analyzed for fiber, carbon (C), and nitrogen (N) content, and decomposition in soil. Lower fiber components and C/N along with higher N are indicators of rapid decomposition. Winter and spring canola stem, root and litter residue differed from one another in fiber and nutrient content, with winter canola having lower fiber C, C/N, and higher N than spring canola. Because winter canola decomposes more rapidly than spring canola and may be used in crop rotations that include summer fallow, winter canola residue must be managed in order to avoid soil erosion, loss of soil organic matter, and degradation of soil quality. Residue from lower rainfall locations and winter canola cultivars shows potential to decompose more rapidly. We did not find clear differences in residue characteristics or decomposition among the seven winter and seven spring canola cultivars tested in the study. We did find, however, that decomposition occurs quickly when residue contains the least amount of all the fiber components, low C/N, and high N. As marketing opportunities for oilseed crops produced in the PNW and worldwide increase, information on residue decomposition will be useful to growers who wish to incorporate canola into reduced tillage crop rotations to increase cropping diversity and prevent soil erosion.