Growth of tropical and temperate grasses at Palmerston North

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Abstract
Small swards of 14 grasses of tropical origin (Cynodon dactylon, Digitaria spp., Paspalum dilatatum, Pennisetum clandestinum, Setaria spp.) and 6 of temperate origin (Dactylis glomerata ''Grasslands Apanui'', Festuca arundinacea, Lolium perenne ''Grasslands Nui'' and ''Grasslands Ruanui'', Phalaris spp.) were established in the field at Palmerston North [New Zealand]. After planting in late spring, herbage samples were taken during Jan.-May of the following summer, dissected into lamina, sheath and remainder (culms, stems, stolons), and analyzed for total N, soluble sugar, starch and in vitro digestibility. Proportion of lamina was 58-96% for the temperate grasses and 31-76% for the tropical grasses. Proportion of sheath was 5-20% for temperate and 22-36% for tropical grasses and for the remainder fraction 0-22% and 2-44%, respectively. Total N content of the lamina was higher than that of the sheath and remainder fractions. There was no clear distinction between temperate or tropical species in N content of the lamina (27.-3.7%), and for entire herbage sample the mean levels ranged from 2.3% (Digitaria smutsii CPI 16778A) to 3.3% (Festuca, Lolium, Pennisetum). Soluble sugar content of the lamina over the season ranged 4.0-8.8% in the temperate grasses and 3.2-4.7% for the tropical species, and the respective ranges for the entire herbage sample were 3.9-8.9% and 2.8-5.0%. Sugar content of a given plant fraction varied up to 2-fold over the summer, some lines having highest values in Jan. and others in April or May. Starch content was less than 1% of the dry weight in each of the 3 fractions. In vitro digestibility of the lamina of the temperature grasses was 68-75% and for the tropical grasses 45-73%, and respective ranges for the entire herbage sample were 68-75% and 52-73%. Mean digestibility over the warm season of herbage from D. smutsii CPI 38869 (C4) did not differ significantly from the same means for the temperature grasses, and the seasonal mean for Phalaris tuberosa ''General Select'' (C3) was similar to that of some tropical grasses.