Achieving Potential Herbage Seed Yields in Tropical Regions

Tropical grass and legume seed production is discussed in terms of potential, presentation and harvested yields. The main structural components of the crop which determine potential seed yield are outlined. Their contributions to presentation and harvested yields are complicated, firstly by the degree of crop synchronisation which reflects changes in these components over time, and secondly by the rate at which ripe seed is shed. Effects of external fnctors on these yield determinants cause variability in production between different years, localities and fnrms. To maximise yields, the location and management of individual herbage seed crops must be based on a sound knowledge of how the particular plant develops and any special flowering requirements it might have. Identification of suitable climates for different herbage seed crops is discussed, together with prospects for seed production in marginal environments. Cultural management practices to meet specific needs of particular grasses and legumes are considered in terms of their effects on potential and presentation yields; these include fertiliser use, defoliation, time of closing, irrigation management and crop hygiene to control weeds, pests and diseases. To maximise seed recovery, the approach to harvesting of different crops also needs to take account of their characteristics. Future improvements in herbage seed yield will come mainly from better physiological understanding of particular grasses and legumes, enabling growers to manipulate seed crops more effectively. Plant breeding should be used to improve herbage seed production only if herbage use is not disadvantaged.