ABSTRACT
Summary Postharvest residue burning, initiated in Oregon in the early 1940s to control blind seed disease in perennial ryegrass (Lolium perenne L.), has been found to be a most effective field sanitation method that also enhances seed yield. It is now a general practice in Oregon, and its use is expanding to other regions. Questions of how burning beneficially affects grass-seed crop production have been the focus of many studies conducted over several years in the Willamette Valley. These studies were given impetus by the concern for clean air in certain locations in Oregon. The objectives of the research were (1) to document the yield response of different species and varieties to postharvest residue burning over a several-year period, (2) to compare burning to alternative methods, such as mechanical removal, for effectiveness in maintaining seed yield, (3) to evaluate relationships of time of burning to subsequent crop yield, and (4) to determine effects of burning on growth characteristics related to seed yield. Investigations carried out over several years examined response to burning and mechanical residue removal of different grass species and varieties in experimental plots at various locations in the Willamette Valley. Results indicated that most species and varieties respond positively in terms of seed yield; however, some show a greater yield response than others. Forage-type perennial ryegrass, orchardgrass (Dactylisglomerata L.), tall fescue (Festuca arundinacea Schreb.), and bentgrass (Agrostis tenuis Sibth.) are less responsive to residue management than is fine fescue (Festuca rubra X,.). Varieties within species respond differently to burning, but in general more effective residue removal results in higher seed yield. Increases in fall tillering and earlier emergence of a larger number of panicles are the basis for seed-yield increases in response to burning. Weed control is improved by postharvest burning. Greater numbers of weeds survive where mechanical methods of residue removal are practiced. Burning early, when straw moisture is low and before regrowth starts, gives superior yields. Burning late, when regrowth has developed and straw moisture is greater, can cause stand injury and is less effective in removing residue. Alternate-year burning is undesirable from the standpoint of seed yield and disease control. Smoke management by burning during meteorological condittions favorable for smoke dispersion is aiding the continuation of the practice of postharvest residue burning by reducing the impact of smoke on population centers. The wide-spectrum nonresidual pest control and yield stimulation provided by postharvest burning make the practice an extremely important tool for grass-seed crops in Oregon and elsewhere where climate permits.
