Mineral concentration and mineral ratios of two Megathyrsus varieties: Effect of swine manure rate and age at harvest of the grasses

This experiment investigated the effect of swine manure rate and age at harvest on the mineral concentration and ratios of two Megathyrsus maximus varieties. The study was a 4 × 2 × 3 factorial experiment in a split-split-plot design with four replications. The calcium concentration ranged from 2.51 g/kg DM for the M. maximus var. Local fertilized at the rate of 100 kg N/ha and harvested at 8 WAP to 5.05 g/kg DM for the unfertilized M. maximus var. Ntchisi harvested at 4 weeks after planting (WAP). The M. maximus var. Local fertilized at 200 kg N/ha harvested at 4 WAP recorded the highest value of phosphorus. The unfertilized M. maximus var. Ntchisi harvested at 12 WAP had the highest Ca:P ratio. The unfertilized M. maximus var. Ntchisi harvested at 12 WAP and M. maximus var. Ntchisi fertilized with 300 kg N/ha harvested at 12 WAP recorded the lowest tetany ratio. M. maximus var. Ntchisi fertilized with 300 kg N/ha and harvested at 8 WAP and 12 WAP having the highest Mn and Fe concentration, respectively. The Fe: Mn ratio ranged between 1.29 and 4.39 for M. maximus var. Ntchisi fertilized with 100 kg N/ha harvested 4 WAP and the same variety fertilized with the same rate of manure but harvested at 12 WAP. In conclusion, the Ca concentrations were observed to be higher in younger grasses (4 WAP), especially the M. maximus var. Local and N concentrations of the grasses decline with maturity across the manure rate. The grasses also recorded tetany ratio values lower than 2.2 as M. maximus var. Ntchisi fertilized with 100 kg N/ha harvested at 8 WAP recorded the lowest value (0.5).