Mineral concentrations in four tropical forages as affected by increasing daylength. II. Microminerals^*

Abstract

Pure stands of the Florakirk and Tifton 85 bermudagrass [Cynodon dactylon (L) Pers.], Florona stargrass (Cynodon nlemfuensis Vanderyst), and Pensacola bahiagrass (Paspalum notatum Fluegge) were established in central Florida during the summer of 1997. Individual grass plots were exposed to an artificial light, which extended the daylength. There were two daylength treatments, extended (artificial light used to maintain daylength at 15 h) and normal daylength conducted over a two-year period. Samples were harvested at distances of 4.0 m ‘behind’ the light and 1.0 m ‘in front’ of the light. Samples were collected and analyzed for iron (Fe), copper (Cu), zinc (Zn), manganese (Mn), and selenium (Se) at six sample dates from the late fall to early spring for two consecutive years, but only one year for Se. There was no difference between normal and extended daylength for Fe, Cu, Zn, and Mn. Forage Cu concentrations increased with extended daylength for Florona stargrass (from 20.3 to 23.1 ppm). Florona stargrass had the highest forage Zn concentrations (90.7 ppm) with normal daylength and had the highest forage Fe and Cu concentrations (130.0 and 23.1 ppm, respectively) with extended daylength. Pensacola bahiagrass had the highest forage Mn concentrations (250.8 ppm) with normal daylength. Forage Se concentrations increased with extended daylength (from 0.033 to 0.042 ppm). Forage Se had the greatest increase with extended daylength for Tifton-85 bermudagrass from 0.028 to 0.049 ppm. The extended daylength did not have a practical difference for concentrations of the five trace minerals. Therefore, there was no improvement on the nutritive value of the forage with an extended daylength. Only forage Se concentrations increased with an extended daylength; however, this was still insufficient to meet the requirements for beef cattle. Iron, Cu, Zn, and Mn concentrations in these four grasses met the requirements for beef cattle.

^*Florida Agriculture Experiment Station Journal Series Number R-08263.

Acknowledgments

Notes

^*Florida Agriculture Experiment Station Journal Series Number R-08263.