Regenerative management and phosphorus fertiliser effects on dryland pasture yield and botanical composition in New Zealand

Abstract

This 3.5‐year grazed farmlet study investigated the impacts of regenerative agriculture and soil phosphorus (P) fertiliser on herbage dry matter (DM) yield and botanical composition in sheep‐grazed dryland pastures. Four treatments compared regenerative with conventional agriculture, under high and low P fertiliser, with Olsen P targets of 10 and 20 mg P kg‾¹. The regenerative system utilised a 12‐species diverse pasture mix with short‐duration grazing and long recovery periods, whereas conventional featured a lucerne (Medicago sativa L.) monoculture with best‐practice grazing. In Year 1, conventional yield outperformed regenerative by 3 t DM ha‾¹ (p<0.01). However, in Years 2 and 3, yields were similar across all treatments, averaging 7.7 t DM ha‾¹ in Year 2 and 10.3 t DM ha‾¹ in Year 3. Fertiliser had a minor effect, with high‐P treatments yielding 796 kg DM ha‾¹ more than low-P (p< 0.01), regardless of management system. In the regenerative treatment, legume content dropped from 34% in spring 2022 to 17% in autumn 2025, while sown grass content increased from 9.5% to 63% over the same period. Unsown species (weeds) contributed more to total herbage DM in conventional than regenerative (p< 0.001), while the proportion of dead material was greater in regenerative (p<0.001). Overall, regenerative matched conventional herbage yield in Years 2 and 3 but showed declining pasture quality due to reduced legume presence. Phosphorus fertiliser had a limited impact on yield and further research is required on how regenerative practices influence P dynamics in dryland pasture soils.