Component Yield and Tissue Composition of Carpon Desmodium- Bahiagrass Pasture as Influenced by Fertilizer Treatment

This research was conducted to determine fertilizer requirement for maintaining a stable bahiagrass (Paspalum notatum Flügge) and Florida carpon desmodium (.Desmodium heterocarpon (L.) DC cv. 'Florida') mixed pasture. Four replicates of seven fertilizer treatments: 56 kg Ν ha"1; 29 kg Ρ ha*1; 56 kg Κ ha'1; 22 kg S ha"1; 45 kg ha"1 of a micronutrient mix containing 24 g Β kg"1, 24 g Cu kg"1, 144 g Fe kg" \ 60 g Μη kg"1, 6 g Mo kg"1, and 56 g Zn kg"1; 29 kg Ρ ha"1 + 56 kg Κ ha"1 + 22 kg S ha"1 + 45 kg micronutrient mix ha*1 (mixed fertilizer); and no fertilizer (control) were randomly assigned to the same 7.6-m by 15.2-m plots in June 1996 and 1997. Metal exclosure cages (2 m by 2 m) were used to protect forage from cattle between June and November. Forage was harvested once in November 1996 and 1997 and separated into grass and legume components. Tissue mineral composition (Ν, Ρ, K, Ca, Mg, Cu, Fe, Μη, Zn, and Β) was analyzed separately for each component. Total (grass + legume) forage dry matter yield (DMY) ranged from 6.3 to 7.8 Mg ha"1, but there was no fertilizer treatment effect. The bahiagrass: carpon desmodium ratio for control DMY averaged 58:42 each year. Relative to the control, Ν application increased the bahiagrass:carpon desmodium DMY ratio to 79:21, whereas the mixed fertilizer treatment decreased the ratio to 44:56. Of the major nutrients, Ρ and Κ fertilizer increased carpon desmodium concentrations for each respective element, Κ fertilizer increased bahiagrass tissue K, and Ν fertilizer had no effect on tissue Ν concentration of either forage. Bahiagrass Ν was increased by the mixed fertilizer. Besides Mg and Β in bahiagrass and Mn and Cu. .in carpon desmodium, no other tissue macro- or micronutrients were altered by fertilizer treatments. The study has demonstrated a need for periodic application of Ρ, K, and micronutrients fertilizer to maintain productivity of grass-legume systems in sub-tropics.