Microbial responses to regenerative and conventional farming practices in dryland pasture systems : A thesis submitted in partial fulfillment of the requirements for the Degree of Master of Agriculture Science ay Lincoln University

Abstract

Regenerative agriculture is proposed as a sustainable farming system that will protect biodiversity and maintain sufficient food production for future generations. The aim of this experiment was to assess the effects of conventional and regenerative farming practices on soil microbiology in a grazed grassland context. The goal was to be able to provide empirical evidence on the outcomes of regenerative versus conventional practices in a New Zealand dryland pasture and whether regenerative farming is a viable and productive option for farmers. The study was conducted at the Lincoln University Regenerative Agriculture Dryland Experiment (RADE) in Lincoln, New Zealand. We focused on block 5 of the experiment, which includes 16 grazed plots arranged in a Latin square design. The treatments included high-phosphorous input conventional agriculture (HCA), high-phosphorous regenerative agriculture (HRA), low-phosphorous input conventional agriculture (LCA), and low-phosphorous regenerative agriculture (LRA). Conventional plots were sown with a cocksfoot/subterranean clover mix, while regenerative plots contained a diverse 12-species pasture blend. Soil samples were collected twice within the experiment, once in the autumn (May 6th, 2024) and once in the spring (October 10th, 2024). Our study focused on how the treatments and seasons impacted potential soil microbial extracellular enzyme activities (EEA), labile nutrient concentrations, microbial functioning, and soil chemical properties. We found that temporal effects had more of an influence on microbial enzyme activities than the treatments (HCA, HRA, LCA, LRA) themselves. Potential microbial enzyme activities increased significantly in the spring, including leucine aminopeptidase (LAP) (P < 0.001), phosphatase (PHOS) (P < 0.01), and β-xylosidase (XYL) (P < 0.05). This was likely driven by seasonal changes in labile nutrient availability, gravimetric soil moisture, and metabolic demand. The only enzyme to show a significant treatment effect was α-glucosidase (AG), which had higher activity under the LRA treatment (P < 0.01). Labile carbon and microbial respiration increased in spring, while labile nitrogen and phosphorus pools declined, suggesting that nutrient cycling was closely tied to seasonal plant growth and microbial activity. Soil properties such as labile nutrients strongly influenced microbial nutrient acquisition ratios, with labile carbon (HWEOC) having the largest impact on both enzymatic C:N and C:P ratios. This study is among the first to explore microbial nutrient acquisition strategies in RA and CA dryland pasture systems. Our findings highlight the potential of regenerative practices to enhance microbial functional capacity under low-phosphorus soil conditions and also emphasise the importance of temporal variability in influencing microbial processes.