Crop density and seed production of tall fescue (Festuca arundinacea Schreber). 2. Reproductive components and seed characteristics

The population density and spatial arrangement of plants may influence the productive life and performance characteristics of a perennial grass-seed c rop. A study was conducted to determine the effects of the initial density (1.6, 3.1, 6.3, 12.5, 25, 50 and 100 plants m(-2)) and row spacing (20, 40, and 80 cm) of plants on reproductive yield components and seed characteris tics of tall fescue (Festuca arundinacea Schreber), over 3 consecutive prod uction years ( 1991-1993) in the Peace region of Canada. The weight proport ion of cleaned-to-uncleaned seed was 85-86% for the three lowest plant dens ities and then decreased, as density increased, to 82% at 12.5 plants m(-2) and 66% at 100 plants m(-2) The 1000-seed weight decreased as density incr eased and ranged from 1.68 to 2.22 g (i.e., 595 000 to 450 000 seeds kg(-1) ). The specific seed weight ranged from 18 to 31 kg hL(-1); it differed amo ng years, but the effect of plant density was inconsistent. The germination capacity of the seed was unaffected by plant density, but differed among y ears; it averaged 87%, 88% and 59% in 1991, 1992 and 1993, respectively. Th e seed yield/plant, the number of panicles/plant, and the number of seeds/p lant decreased exponentially as plant density increased. The number of clea n seeds/panicle decreased, as plant density increased, in the first year bu t was less affected subsequently, particularly with the 20-cm row spacing. The seed yield was correlated closely with the number of panicles m(-2) (r = 0.659***). An initial density no greater than 25 plants m(-2) in rows spa ced 20-40 cm apart enhanced seed quality by producing a greater proportion of clean seed which had a higher 1000-seed weight. Such a plant density, ho wever, is at the low end of the optimum range for maximizing seed yield per unit land area.