Seedling vigor enhancement by tiller density management in seed production of perennial grass (Agropyron elongatum Host)

Considering seed quality beside production quantity is essential in range seed production stations. A field experiment was conducted to evaluate tiller density effect on seed characteristics and yield in 2005 at the Nyshaboor station. Five treatments in tiller removing including 50% as row full removal every other ones, 50% (250 tillers), 65% (325 tillers), and 75% (375 tillers) on long row, and plus control (500 tiller per m2) were applied on 3 or 6 years old plants at booting stage in A. elongatum. After ripening seed, seed yield, seed purity and seedling vigor (root and shoot dry weight under hydroponics condition) were measured. The experiment was conducted as combination factorial (plant age and tiller density) using completely randomized design with four replicates. The results showed that 3 years old plants were better than 6 years old for seed yield and qualitative characters (P<%5). Thinning treatments had no effects on germination percentages. Yield reduction by 17 and 40% occurred with 50 and 75% tiller removal respectively compared to control. Decreasing density by75% resulted in increased root and shoot dry weights, seedling vigor and seed purity by 5, 12, 12, and 8 percent respectively. These results suggest that for high seed quality supply the plant density should be reduced at least 50% at this station. Also, better management is needed for increasing seed yield and seedling vigor by decreasing tiller production and vegetative growth to allocate more carbohydrates to seed production.