The effect of cutting interval and associate grass species on the growth of Stylosanthes species near Ingham, north Queensland

Abstract

Five Stylosanthes guianensis accessions (cvv. Schofield, Cook and Endeavour, CPI 33706 and 40294), four S. scabra accessions (cv. Seca, CPI 34925,40205 and 40289), two S. viscosa accessions (CPI 33941 and 40264 B) and Centrosema pubescens (Common centro) were grown in small, fertilized swards with either Brachiaria decumbens cv. Basilisk or Panicummaximum near lngham in northern Queensland. The swards were cut every 4,8,12 or 16 weeks to 10 cm above the ground for three years and herbage yield and botanical composition measured. Herbage yields of all Stylosanthes accessions declined over the three years while those of C. pubescens and the sown grasses increased after the first year. In the final year S, viscosa accessions yielded 200 kg ha-1 of dry matter or less, S. scabra accessions less than 2000 kg ha-1 and S. guianensis accessions and C. pubescens more than 2000 kg ha-1. The yields and proportions of legume and miscellaneous species were lower in B, decumbens plots than P. maximum plots. After the first year, cutting interval had no effect on legume yield. Grass yields were similar with cutting intervals of 12 or 16 weeks, but when plots were cut every 4 or 8 weeks B. decumbens outyielded P. maximum. The legume content of the S, guianensis plots cut every 12 or 16 weeks was higher than that of those cut every 4 or 8 weeks. The proportion of C, pubescens in the swards increased linearly as cutting interval increased. S. guianensis cvv. Schofield and Cook, and CPI 40294 had high growth rates early in the growing season while S. guianensis cvv. Schofield, Cook and CPI 33706 had high growth rates late in the season. B, decumbens had a higher growth rate than P. maximum during both the early and late growing season periods. S. guianensis cv. Cook was the best legume accession but S. guianensis CPI 40294 and S. scabra require further testing. None of the new accessions was more compatible with B. decumbens than existing cultivars.