Effects of seeding density, cutting height and month of harvest on the dry matter yield and protein content of Ubon Stylo

Abstract

Four levels of seed were used for establishment of Ubon Stylo (Stylosanthes guianensis var. vulgaris x var. pauciflora) in the first phase of this research, and in the present second phase, this same variable plus three cutting heights and four months of harvest at 90-d intervals were evaluated as to their effects on forage dry matter yield (DMY) and crude protein (CP) content. The seeding levels (5, 10, 15 and 20 kg/ha) constitute the main plots; cutting heights (10, 15 and 20 cm) formed the subplots; and months of harvest (March, June, September and December) the sub-subplots. Statistical analysis revealed that DMY was not significantly influenced by cutting height or by the interactions of this variable with each of the other two. Month of harvest did exert a significant effect (P<0.05) on DMY, and seeding density showed a similar tendency (P<0.063); also an interaction (P<0.05) between these two variables was detected. Mean DMY, expressed as annual equivalent (kg/ha), corresponding to the four consecutive harvests from March to December were: 5,949; 11,285; 8,105 and 6,543; with a general mean of 7,970. Values of DMY corresponding to the four progressive seeding rates from 5 to 20 kg/ha seed were: 7,488; 8,347; 8,375 and 7,672 kg/ha. The seeding rate x harvest interaction is illustrated by the fact that the highest DMY at the June harvest (13,975 kg/ha) was obtained with 15 kg/ha seed, whereas the maximum DMY at the other three harvests corresponded to the 10 kg/ha seeding rate. The general mean of the forage CP content was 13.4% and no significant effects were exerted by the three factors under study or their interactions. The present results confirm the earlier conclusion that 10 kg/ha is the optimum seeding rate for establishment of Ubon Stylo to promote a high DMY without incurring in unnecessary additional expense. Furthermore, the high yields obtained in the summer season suggest that the cutting interval could be shortened to improve the CP content at this time of year.