ISSN: 0041-3216 (Online), 0041-3216 (Print)
Volume 54 Number 2
Nitrogenase activity, nitrogen content, in vitro digestibility and yield of 30 tropical forage grasses in Brazil*
Dinitrogen fixation nitrogen content in vitro organic matter digestibility (IVOMD) and yield were determined on 26 digitgrass breeding lines and four commercial cultivars of digitgrass and Bermuda grass. Commercial lines tested were 'Pangola', 'Transvala' and 'Slenderstem' digitgrass, and 'Coast-cross-1' Bermuda grass. After establishment, 13 harvests were made, once every 28 days during 1974. During the year, cumulative dry matter yield ranged from 16711 to over 30000kg/ha. Production rates of commercially available cultivar were intermediate and not significantly different from each other. Three of the breeding lines of digitgrass had significantly higher yields than the four commercial cultivars. Five of the breeding lines were signifi-cantly higher in yield than 'Slenderstem' and 'Pangola'. The highest yielding experimental hybrid also had the highest digestibility (68·2 per cent IVOMD). The three best breeding lines averaged 761 kg of per hectare per year in the forage harvested, whereas only 200 kg N/ha/yr was applied. Nitrogenase activity of roots measured by acetylene reduction on soil-plant cores indicated that rates of over 500g /ha/day could be fixed under favourable conditions. Nitrogen content of soil and plant material harvested from each plot was also monitored during the year.