Studies with Urochloa brizantha cv. MG5 Vitória in Okinawa, Japan: Vegetative propagation and a tractor tyre stress test

Feeding of high quality grass is critical to ensure breeding cows remain healthy with high reproductive rates and growing and fattening cattle achieve good growth rates. The Brazilian grass cultivar, Urochloa brizantha cv. MG5 Vitória, is highly nutritious and is known for its drought tolerance. In view of its low seed production potential in subtropical Japan and of phytosanitary problems (contamination with soil particles) of imported seed, a study was conducted in Okinawa to assess 2 methods of propagating this cultivar vegetatively. Cutting stems (culms) at about 10 cm from ground level and inserting them 3 cm into a 50:50 compost:soil mixture produced a 77% success rate in terms of rooted plantlets in a glasshouse compared with 67% for cutting the culm at 3 nodes from the base, subsequently allowing 2 weeks for adventitious roots to form on the lowest node, then cutting below the node where roots emerged and planting the rooted propagule in the same mixture. It seems that the simple process of cutting stems at about 10 cm from ground level and inserting them into a suitable mixture of soil and compost should result in an acceptable yield of plantlets for establishment of an MG5 forage crop. However, locating a source of high-quality seed free of phytosanitary problems seed would seem to be a better solution to increase the areas in Okinawa planted to MG5. In the tractor tyre stress trial conducted over 2 years, an MG5 forage crop established from seed showed depressed yields on the treatment subjected to tractor tyre pressure but performed as well as Chloris gayana, a much-used forage grass in Okinawa.