Effects of intensity and frequency of defoliation on a mixture of guinea grass (Panicum maximum cv. Coloniao) and Verano stylo (Stylosanthes hamata cv. Verano) : a thesis presented in partial fulfilment of the requirements for the degree of Master of Agricultural Science in Plant Science at Massey University
A study was conducted in a glasshouse to determine the effect of defoliation treatments comprising combinations of two intensities (7.5 cm and 15.0 cm cutting height) and three frequencies (2, 3 and 6 weeks) on production, botanical composition and crude protein of a Guinea grass (Panicum maximum cv. Coloniao) / Verano stylo (Stylosanthes hamata cv. Verano) sward. Total cumulative yield was reduced with more intense defoliation and decreased as the sward was defoliated more frequently. A similar response was observed for cumulative grass yield. In legume, cumulative yield was reduced at hard intensity but was not influenced by defoliation frequency. The proportion of the legume component in the sward was not influenced by defoliation intensity but increased with increasing defoliation frequency due more to depressed grass growth rather than a promotion in legume growth. Defoliation intensity and defoliation frequency had no effect on legume branch number. Similarly, branch size was not influenced by defoliation frequency but increased with less intense defoliation. Both defoliation intensity and defoliation frequency influenced grass tiller number. It was increased with more intense defoliation. The sward defoliated at moderate frequency resulted in the highest tiller number. Tiller number was not different between very frequent and infrequent defoliation. Intensity and frequency of defoliation also influenced average tiller size. It was reduced with more intense defoliation and decreased with increasing defoliation frequency. Percent crude protein content of both grass and legume was not influenced by defoliation intensity but was reduced with less frequent defoliation. The percent crude protein content in the legume which was more than double that in the grass indicates that Verano stylo has important contributions in the development and management of a legume-based tropical pasture.