Tillage and establishment system effects on annual ryegrass seed crops

Annual ryegrass [Lolium perenne L. ssp. multiflorum (Lam.) Husnot] seed crops have been produced on some Oregon farms continuously for decades without rotation of crops or farming practices. The objective of the study was to determine the effects of tillage and establishment systems on 'Gulf' annual ryegrass seed crops over a 9-year period. Six systems were employed: (i) continuous conventional tillage (CT), (ii) continuous no-till (NT), (iii) NT/CT cycle alternate year tillage (NT/CT), (iv) volunteer/CT cycle alternate year tillage (Vol/CT), (v) burn and NT/CT cycle alternate year tillage (Burn + NT/CT), and (vi) volunteer/NT/CT cycle with tillage every 3rd year (Vol/NT/CT). Environment × system interaction effects governed seed production characteristics. Three seed yield environments were observed during the 9 years: high, intermediate, and low. High yield environments had higher temperatures (+1.2 °C) and lower precipitation (−48 mm) in April-June than in low yield environments. Across environments, yields were greatest with Burn + NT/CT, CT, and Vol/NT/CT and lowest with NT. Stability analysis revealed that Burn + NT/CT, CT, and Vol/NT/CT systems produced up to 40% greater yields than the mean of all systems in low yield environments. Yield variation among systems was high in low yield environments. Increasing tillage frequency from zero in NT to once every other year in NT/CT boosted yields so that they were equivalent to CT. Yield differences among systems were attributable to seed number. Moderate tillage frequency and occasional residue removal are required to produce the best long-term seed yields in annual ryegrass.