Residue management of perennial ryegrass and tall fescue seed crops

Regulations on open-field burning have forced grass seed growers to adopt alternatives for postharvest residue management. Experiments were conducted on fields established by grass seed producers in western Oregon to compare effects of (i) mechanical straw removal and flail-chopping the stubble (flail-chop), (ii) mechanical straw removal and propane-burning the stubble (propane-burn), and (iii) open-field burning the residue (open-burn) on seed yield the following year. Treatments were tested on three consecutive crop years of perennial ryegrass (Lolium perenne L. cv. Regal and Pleasure) and tall fescue (Festuca arundinacea Schreb. cv. Martin and Rebel II). Seed yield components were measured to identify the components through which treatments affect yield. Treatments did not affect seed yield of Regal perennial ryegrass and Martin tall fescue in any crop year. Third-crop seed yield of Pleasure perennial ryegrass was 15% higher for the open-burn than for the flail-chop treatment; fourth-crop seed yield was 12% higher for the open-burn treatment than for either flail-chop or propane-burn. Across years, seed yields of Rebel II tall fescue for propane-burn and open-burn treatments were 8 and 12% greater, respectively, than for flail-chop. Where seed yields were affected, differences among treatments were through changes in seed number per unit area (seeds m(-2)), but seed weight was relatively stable. Treatments did not affect the number of fertile tillers in any cultivar. Variations in seed number were apparently due to treatment effects on the number of seeds set per tiller. We conclude that the need for postharvest residue burning in perennial ryegrass and tall fescue is cultivar specific. Mechanical residue removal is apparently as effective as open-field burning for maintaining high seed yields in some cultivars of these grasses.