Influence of fertilizer on component yield and tissue composition of carpon desmodium-bahiagrass pasture

This research was conducted to evaluate fertilizer required to maintain bot anical stability of a bahiagrass (Paspalum notatum Flugge) and Florida carp on desmodium (Desmodium heterocarpon (L.) DC cv. 'Florida') pasture. Four r eplicates of seven fertilizer treatments: 56 kg N ha(-1) [50 lb N acre(-1)] ; 29 kg P ha(-1) [60 lb P2O5 acre(-1)]; 56 kg K ha(-1) [60 lb K2O acre(-1)] ; 22 kg 8 ha(-1) [20 lb 8 acre(-1)]; 45 kg ha(-1) [40 lb acre(-1)] of a mic ronutrient mix containing 24 g B kg(-1), 24 g Cu kg(-1), 144 g Fe kg(-1), 6 0 g Mn kg(-1), 6 g Mo kg(-1), and 56 g Zn kg(-1); 29 kg P ha(-1) + 56 kg K ha(-1) + 22 kg 8 ha(-1) + 45 kg micronutrient mix ha(-1) (mixed fertilizer) ; and no fertilizer (control) were randomly assigned to the same 7.6-m by 1 5.2-m (25' by 50') 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 gras s and legume components. Tissue mineral composition (N, P, K, Ca, Mg, Cu, F e, Mn, Zn, and B) was analyzed separately for each component. Total (grass + legume) forage dry matter yield (DMY) ranged from 6.3 to 7.8 Mg ha(-1) (2 .8 to 3.5 ton acre(-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, N application increased the bahiagrass:carpon des modium DMY ratio to 79:21, whereas the mixed fertilizer treatment decreased the ratio to 44:56. Of the major nutrients, P and K fertilizer increased c arpon desmodium concentrations for each respective element, K fertilizer in creased bahiagrass tissue K, and N fertilizer had no effect on tissue N con centration of either forage. Bahiagrass N was increased by the mixed fertil izer. Besides Mg and B in bahiagrass and Mn and Cu in carpon desmodium, no other tissue macro- or micronutrients were altered by fertilizer treatments . This study has demonstrated a need for periodic application of P, K, and micronutrients fertilizer to maintain productivity of grass-legume systems in Florida, and has provided some information on tissue mineral concentrati ons in a bahiagrass-carpon desmodiun pasture.