Mechanical weeding boosts ecosystem functions and profits in industrial oil palm, study finds

Oil palms are the highest-yielding oil crop and global demand is increasing. However, their productivity is due to traditional management practices, including heavy use of fertilizers and herbicide application, resulting in severe environmental damage.

A new study by an international, multidisciplinary research team led by the University of Göttingen shows that switching to mechanical weeding and reducing fertilizer use result in a significant increase in both ecosystem multifunctionality and profit. Scientists compared different environmental measures and economic indicators in mechanical weed control, herbicide application and combinations thereof with high and reduced fertilizer use. Their study was published in the journal nature sustainability.

Oil palm production has increased in Indonesia, currently the world’s largest palm oil producer, coinciding with the country’s increasing rate of deforestation. Although oil palm production has brought socioeconomic benefits, it also causes environmental problems such as biodiversity loss, nitrate leaching, and greenhouse gas emissions.

The team conducted their research in plantations that were at least 16 years old, beginning in 2016 in Jambi, Indonesia, with the aim of testing reduced management versus conventional practices. They studied the effects of reducing fertilizer use to compensate for the amount of nutrients removed by harvesting oil palm fruit and mechanical weed control with a brushcutter. Over four years, researchers collected data on oil palm yield, material and labor costs, animals both below and above ground, soil vegetation diversity, greenhouse gas emissions, soil fertility, and nutrient leaching.

“Despite reduced fertilizer use, oil palm yields are similar to conventional farming, but profit increases significantly due to the reduction in fertilizer costs. Biodiversity also improves significantly, driven by the increase in ground vegetation species with mechanical weed control,” says first author Dr. Najeeb Al-Amin Iddris from the Department of Soil Science in Tropical and Subtropical Ecosystems at the University of Göttingen. Because ecosystem functions are typically interrelated, the analysis was conducted across multiple ecosystem functions, known as “multifunctionality”.

“Mechanical weed control shows a significantly higher multifunctionality of the ecosystem than the application of herbicides. It promotes rapid recovery of soil vegetation and increases its biodiversity, which can improve recycling of nutrients via root uptake, and combined with reduced fertilizer use reduces leaching and increases nutrient retention in the soil,” explains Iddris.

“The study found no reduction in greenhouse gas emissions from reduced fertilizer use and mechanical weeding over the four years of this experiment. The consequences of more than 15 years of conventional management prior to the start of the experiment may have dampened the effects of reduced management. ‘ explains first author Dr. Marife Corre, University of Goettingen.

“The positive effects of mechanical weed control on ecosystem multifunctionality and gain demonstrate that such intelligent practices can bring benefits even over a short period of time. Using mechanical weed control early in the establishment of an oil palm plantation can bring even greater benefits,” says Corre.

“These management practices can be easily adopted in practice and should be included as one of the criteria for the production of sustainable palm oil, as set out by the Roundtable on Sustainable Palm Oil, an organization of oil palm producers, processors, manufacturers, investors, and environmental groups and stakeholders in social development.”