Potential of new summer grasses in Northland

Abstract

Herbage of 22 C₄ grasses and 3 C₃ grasses grown in Northland was analysed for nutritive quality. Small swards of the grasses were cut at approximately 5-weekly intervals from mid November to mid April to provide forage samples. Digestibility of leaf and stem tissue of a representative range of these grasses assessed by an in vitro technique was not altered significantly by irrigation, and did not alter significantly during the warm-season growth period. Leaf and stem tissue of the various grasses did vary substantially in digestibility, stem tissue usually being lower in digestibility than leaf tissue. Some of the C₄ grasses had dry matter digestibilities equivalent to those of the C₃ species. The digestibility of herbage from grasses grown at Kaitaia, New Zealand, was frequently higher than that of the same grasses grown in a warmer environment at Lawes, Australia. Crude protein, alcohol soluble sugar, and starch levels were also measured in leaf and stem tissue of the grasses. Crude protein levels in leaves of most of the grasses appear sufficient to maintain milk production in cows, but stem material levels do not. Mature, stemmy regrowth of many of the C₄ grasses could be seriously deficient in protein. Most of the C₄ grasses produced herbage with one or more nutritive quality problems, but the variability observed in even this limited sampling suggests that it could be possible to find or produce types with improved overall quality. A summary of the more important agronomic and nutritive features of the grasses is given.