75 Years at Ukulinga: What the World’s Longest Grassland Experiments Reveal About Fire, Fertility and Biodiversity

The Ukulinga Research Farm, just outside Pietermaritzburg, South Africa, has hosted continuous grassland experiments since 1950. Located on a species-rich grassland with scattered trees in a region where grasslands and savannas cover more than 60% of the country, Ukulinga provides forage for livestock and wildlife and delivers key ecosystem services such as water regulation, carbon storage, biodiversity, cultural values and recreation.

Long-term experiments and their origins

In 1950 Professor J.D. Scott established two complex field trials: the Veld Burning and Mowing Trial and the Veld Fertilisation Trial (now the Ukulinga Grassland Fire Experiment and the Ukulinga Grassland Nutrient Experiment). Originally designed to improve hay yields and forage quality, both experiments have run without interruption for 75 years and have become invaluable long-term ecological laboratories.

Why duration matters

The experiments’ greatest scientific strength is their uninterrupted duration and the consistent application of treatments—prescribed burning, mowing and nutrient addition—over decades. These sustained manipulations reveal slow ecological processes, long-term interactions and tipping points that short-term studies cannot detect.

Key findings

• Disturbance versus exclusion: Plots from which fire and mowing were withheld converted into dense, woody thickets, fundamentally shifting plant composition and ecosystem function. Regularly burned or mown plots retained productive, species-rich grassland structure.
• Nutrient enrichment effects: Nitrogen and phosphorus fertilisers increase short-term productivity but favour fast-growing grasses and, over time, reduce native plant diversity—demonstrating how artificial enrichment drives different outcomes from natural disturbance regimes.
• Grazing systems: Mid-20th-century livestock trials comparing continuous, rotational and rest systems, and later multi-paddock rotational studies, showed complex relationships between grazing intensity, plant resilience and productivity that continue to inform rangeland management.

Research scope and influence

Studies at Ukulinga span molecular and microbial work through plant-community and ecosystem-level research, covering fire effects, nutrient cycling, soil processes, biodiversity responses and remote sensing. To date the experiments have produced around 50 peer-reviewed papers; the most-cited studies have reached an international audience, with citations and collaborations spanning many countries.

Education, outreach and global networks

Ukulinga has trained generations of students and hosted visiting researchers who have carried practical lessons into conservation, policy and management across South Africa. The site now hosts international collaborative networks such as the Nutrient Network (NutNet), DroughtNet and DragNet (Disturbance and Recovery Across Global Grasslands), allowing direct comparisons of long-term data with sites worldwide.

Preservation and future value

Because some ecological responses and tipping points only emerge over decades, preserving these continuous long-term experiments is critical. Maintaining the original burning, mowing and nutrient-addition treatments without alteration ensures that Ukulinga remains a unique platform for testing new hypotheses, monitoring slow ecological change, and guiding sustainable grassland management under emerging pressures such as climate change.

Author: Craig Morris, University of KwaZulu-Natal