Nitrogen rates in seed production of two contrasting cultivars of common bent (Agrostis capillaris)

Abstract

Field trials comparing various combinations of 0, 30 or 60 kg N ha−1 in autumn (September) and/or spring (April) to seed crops of common bent (syn. browntop, US: colonial bentgrass, Agrostis capillaris L.) ‘Leikvin’ (main use: long-lasting pastures and utility turf) and ‘Nor’ (main use: lawns and golf course fairways) were carried out on silt loam soils at Landvik, south-east Norway (58°N) from 1989 to 1994. One trial per cultivar was established in 1989, 1990 and 1991, each trial being harvested for three years. On average, for nine harvests and nine N treatments, ‘Leikvin’ and ‘Nor’ gave seed yields of 276 and 128 kg ha-1, respectively. Seed yields of ‘Leikvin’ increased with increasing N rate up to 60 kg N ha−1 in autumn and 30 kg N ha−1 in spring; no interaction between autumn and spring N rate could be detected in this cultivar. In ‘Nor’, a significant autumn x spring rate interaction indicated a linear seed yield response to N in spring on plots that had received 60 kg N ha−1 in autumn, but a diminishing response to N in spring on plots that had received 0 or 30 kg N ha-1 in autumn; the highest seed yield was produced with autumn + spring applications of 60 + 60 kg N ha−1 in this lawn cultivar. While panicle number and seed number per panicle were equally important for seed yield in ‘Leikvin’, panicle number had the stronger impact on seed yield in'Nor'. Seed crops of ‘Leikvin’ were generally taller and more susceptible to lodging than seed crops of ‘Nor’. Year-to-year variations in seed yield level and optimal N regime were less related to crop age than to weather conditions and seed crop management. Given the present prices for fertilizer and seed, it is concluded that Norwegian seed crops of common bent should receive 50–60 kg N ha−1 in autumn regardless of cultivar. Economically optimal N rates in spring are 30 and 60 kg N ha−1 to ‘Leikvin’ and ‘Nor’, respectively.