The research was unable to identify changes to FFB yield of oil palm blocks with up to 33 rounds of rotational cattle grazing. Factors that most strongly influenced block FFB yields were the number of production palms per block and rainfall prior to harvest. In contrast, the rotational grazing of cattle had no statistically significant impact. Other oil palm plantations have however reported an increase in FFB yield due to the impact of grazing cattle.
The spread of Ganoderma by grazing cattle was also investigated through laboratory experiments. Ganoderma spores were unviable after being immersed in rumen fluid and cattle faeces was found to retard the spread of Ganoderma infection. It was concluded that rotational cattle grazing was unlikely to be a significant factor in the spread of Ganoderma in oil palm plantations.
Soil chemical analysis identified slight increases in soil carbon, cation exchange capacity (CEC) and phosphorus concentration in grazed blocks compared with ungrazed blocks, particularly during the dry season. Denitrifying bacteria tended to increase with cattle grazing during the wet season, but not to levels that impacted plant growth. The increases in denitrifying bacteria may occur in response to the increase in soil carbon. Increases in soil bulk density and soil compaction due to grazing were identified but remained below levels likely to restrict plant root growth. Results were however inconsistent, probably due to the high natural variability of these factors within the landscape.
The requirement for under-palm weeding was significantly reduced by grazing cattle. Reductions in labour and herbicides resulted in savings of between IDR50,000 and IDR70,000 per hectare per year. Cattle also provided free organic fertilizer in the form of cattle dung.
The full research report will be out in the coming quarter and will be published on the BPPT and IACCB/RMCP websites.