Browsing by Person "Kurtz, Ditmar Bernardo"

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    Management of excess standing biomass in Argentinean grasslands to increase grass and livestock productivity
    (2016) Kurtz, Ditmar Bernardo; Asch, Folkard
    Grasslands are the main source of feed for cattle in Argentina. Standing dead biomass (SDB) accumulation threatens efficient resource use. To reduce dead biomass pools in Northern Argentinean rangelands, high impact grazing (HIG) was proposed as an alternative to both, mechanical elimination and the use of fire. However, the effects of HIG on grasslands’ biomass accumulation, diversity and forage quality are unknown. The effect and timing of HIG by cattle was therefore studied in grasslands of North Eastern Argentina. We introduced HIG monthly, on adjacent paddocks over the course of the year and its effects were studied for 12 months following the treatment. Dynamics of biomass re-growth, accumulation of green and standing dead biomass were studied. Additionally, the effects of HIG on plant species composition and the forage quality parameters were monitored and evaluated. The immediate effect of HIG was the reduction of the standing biomass by more than 95%. HIG generally improved the green to total biomass ratio and reduced the overall biomass in the paddocks. All sub-plots subjected to HIG showed a growth pattern anti-cyclic to control, with an active growth phase during autumn when the biomass in the control sub-plots decreased. Best results in terms of SDB reduction and dead to green biomass ratios were achieved after HIG in winter. HIG in autumn, however, reduced fodder availability and reduced from then on, grasslands productivity. Irrespective of the season HIG was applied, the grassland recovered completely with regard to species richness and diversity, the Shannon-Wiener diversity index (H) and the Shannon’s equitability index (E) did not reveal any difference within 12-month period after HIG. Our results suggest that HIG is not shifting plant species composition to a more ruderal strategy based plant community, but instead promotes previously established rather competitive and higher value fodder species. Our results indicate that HIG improves the nutritive value of the green biomass due to increased crude protein (CP), digestible organic matter (DOM), and (metabolizable energy) ME, but if applied in summer it has no evident positive effect. On an area basis, grassland subjected to HIG provided enough monthly ME and CP to meet the requirements of the current stocking density in Corrientes. HIG could be an alternative management practice, to fire and other mechanical SDB elimination, towards sustainable intensification. However, we are aware that long-term observations with repeated HIG should be analysed to detect possible delayed effects and interactions especially with seasonal variability.