Comparison of enhanced, tame Italian ryegrass (Lolium multiflorum L.), long established and naturally reseeded, versus an annual ryegrass crop in the flood plain of Río Salado, Argentina: Winter forage production under grazing

Abstract

Effective operation of grazing production systems requires controlling forage availability at the farm level. A nine-year-old stand of enhanced native ryegrass (Lolium multiflorum L.) (RGE) and an annual crop of Italian ryegrass (Lolium multiflorum L. cv Tama) (RGT) were monitored to test the hypotheses that: (1) herbage biomass in such pastures can be assessed by Ration Calculation methodology as accurately as by more exhaustive procedures, and (2) enhancement increases quantity and quality of the winter forage supply. Enhancement includes fertilization with NH4NO3 and (NH4)2HPO4, and weed control with Glyphosate. The Ration Calculation method estimates available herbage dry matter assuming that «one herbage ration» is equal to one cow equivalent (CE), consisting of 10 kg DM day-1 with 77.57 MJ of ME. Herbage samples were taken from each paddock, representing harvestable biomass. Grazing harvest efficiency and herbage DM intake (HDMI) were estimated through the difference between initial (IHA) and final (FHA) herbage available (kg DM ha-1), before and after grazing, corrected for losses due to grazing. Eight grazing cycles of RGE produced annually 16 041 kg DM/ha, (2 001 ± 79.3 rations/ha) while ration calculation estimated 9 775 kg DM/ha. The RGT allowed seven annual grazing cycles, yielded 12 269 kg DM/ha or 1 144 ± 87.1 rations/ha compared to 8 688 kg DM/ha estimated by calculating rations. The latter method did not accurately assess the enhanced cumulative herbage DM produced. Enhancement technology improved production and quality of tame ryegrass in winter.