Tropical Grasslands (1992) Volume 26, 206211
Performance of yearling steers grazing bahia grass pastures with summer annual legumes or nitrogen fertiliser in subtropical Florida
W.D. PITMAN1, K.M. PORTIER2, C.G. CHAMBLISS3 and A.E. KRETSCHMER, Jr.4
1University of Florida, Agricultural Research Centre, Ona, Florida, USA;
In the subtropics, bahia grass (Paspalum notatum) is a widely adapted but low-quality pasture grass. In peninsular Florida it is the predominant pasture grass, and levels of cattle production supported are typically low. Established pastures of bahia grass with either aeschynomene (Aeschynomene americana), phasey bean (Macroptilium lathyroides), or nitrogen fertiliser were evaluated over 3 years at Ona, Florida, USA for potential to provide sustainable pasture systems of increased productivity. Aeschynomene pastures produced the highest average daily gains (ADG) of yearling steers at 0.57 kg compared with an average of 0.36 kg for the other treatments. Crude protein (CP) concentration of legumes was high (over 20%), however, the legumes comprised only 7.2% (for aeschynomene) and 2.3% (for phasey bean) of the herbage dry matter during the peak period and did not increase CP or in vitro organic matter digestibility (IVOMD) of total herbage samples even during this period. The high nitrogen treatment (224 kg/ha N) produced higher (P < 0.05) total herbage CP and IVOMD than did the zero N control (12.9% CP vs. 8.8% and 48.8% IVOMD vs. 42.3%) but did not produce higher (P > 0.10) ADG. Carrying capacity was lowest on aeschynomene (536 d/ha) and highest at 224 kg/ha N (1322 d/ha). During the late summer period in 1983 and 1984, when aeschynomene comprised 12% and 6% respectively of the available herbage dry weight, ADG of 1.70 and 1.46 kg on the aeschynomene treatment substantially exceeded (P < 0.05) that of 0.79 and 0.84 kg on the control for that period. Stands of the legumes were not sustained, apparently due to dense grass sod and erratic rainfall. N fertilisation of bahia grass increased carrying capacity but failed to enhance individual animal performance despite increases in forage quality.