The current world population of 8 billion is projected to increase to 10 billion by 2050. This population would increase global food demand by 70% from what was required 10 years ago. The intensification of production and government policies have led to a reduced diversity of agricultural production worldwide. The homogenization and specialization of agriculture that has been seen over the past 50 years reduces the sustainability and resilience of these systems. For global food production to become sustainable whilst feeding the projected population of 10 billion, it needs to operate using no additional land to what is used currently. Therefore, the efficiency of current farming systems needs to increase to achieve this.
Practitioners of regenerative agriculture claim that this system can increase the water use efficiency of grassland production through increased yields and reduced inputs and losses of water. My honours project reported the effects of regenerative agriculture on the water use efficiency of grassland production from a 10 ha farmlet-scale experiment. This was done at at Lincoln University, where two systems of grassland-based sheep production – a regenerative agriculture system comprising multi-species forages and ‘long-rotation’ grazing (RA) and a conventional agriculture system comprising standard forages and standard grazing techniques (CA) – were compared across soils with low and high inputs of phosphorus fertiliser.
The yield was 585 kg DM/ha lower, water use was similar, and water use efficiency was 2.3 kg DM/ha per mm lower for the regenerative system (2025 kg DM/ha, 199.4 mm, and 10.8 kg DM/ha per mm) compared with the conventional system. There were no effects of fertiliser input. This was best represented in the Latin Square containing a 12-species pasture mixture for the regenerative plots and a ‘Kaituna’ lucerne monoculture for the conventional sward. Under their respective managements, the regenerative pastures produced 62% less yield than the conventional pastures. This resulted in the water use efficiency being 5.7 kg DM/ha/mm lower in the regenerative plots for Latin Square 1. The other four Latin squares showed no difference in water use efficiency, suggesting that there are pasture mixtures that can have similar productivity under regenerative management to conventional systems.
Improved water use efficiency was reflected in higher nitrogen contents and lower post-grazing pasture mass and ground cover. The weed content and dead material of regenerative swards were lower than in conventional pastures. Lucerne was recognised as a key component in the increasing water use efficiency, thus, sward management should optimise the productivity of lucerne. Overall, this study suggests that regenerative systems, as they currently stand, reduce the yield and water use efficiency of unirrigated grassland production.
