Impact of regenerative agriculture on radiation use efficiency of grassland production: A Dissertation submitted in partial fulfilment of the requirements for the Degree of Bachelor of Agricultural Science with Honours at Lincoln University

Abstract

Regenerative agriculture has received more and more attention within recent years and has been promoted as a method to mitigate climate change by increasing soil carbon storage. Furthermore it is described as a way to increase biodiversity, provide a solution for declining health of freshwater ecosystems and water quality, and improve the wellbeing of farmers and communities. The aim of this dissertation was to investigate the effectiveness of regenerative agriculture for improving the radiation (light) use efficiency of grassland production. A dataset of grassland radiation-use efficiency and explanatory variables was collected from 4.5 months (15 February to 28 June 2023) of a new farmlet-scale experiment, the “Regenerative Agriculture Dryland Experiment” (RADE) at Lincoln University, New Zealand. The experiment compared two systems of grassland-based sheep production, a regenerative agriculture system comprising species-rich pastures and long-rotation grazing and a conventional agriculture system comprising standard pastures and grazing techniques, across soils with low and high inputs of phosphorus fertiliser. The four treatments were established as four 2-ha farmlets of 20 paddocks between 10 December 2021 and 16 March 2023.Incoming and transmitted photosynthetically active radiation (PAR) were measured with a SunScan for every plot before and after every defoliation and once a month for all plots concurrently. Samples of pasture mass of each plot were taken by the RADE team. Radiation use efficiency was calculated from accumulated yield and intercepted PAR. Yield, intercepted PAR, radiation use efficiency, farm cover, post grazing pasture mass, and proportion of dead and weed of biomass and nitrogen content was subjected to analyses of variance and a linear regression analysis for recovery of pasture was undertaken. The results indicate that, after the four and a half month, the regenerative system accumulated a lower yield than the conventionalsystem (2347 kg DM/ha vs. 3354 kg/ha), a greater accumulated intercepted PAR (612 MJ/m2 vs. 530 MJ/m2 vs.), and a lower mean radiation use efficiency (0.389 g/MJ vs. 0.646 g/MJ). Furthermore, it was found that, in the regenerative plots, post grazing pasture mass was higher by 943 kg DM/ha, and average farm cover was higher throughout the measuring period, but rate of recovery was not different (19.74 kg DM/ha/day) when compared to the conventional pastures. A higher proportion of dead material (0.35 vs. 0.24), but lower proportion of weeds (0.03 vs. 0.013) were found in the regenerative pasture. Nitrogen content of pasture dry weight was lower for the regenerative system (2.44% vs 3.07%). Differences between fertility levels and system-fertility interaction were found to be non-significant. The higher radiation use efficiency of the conventionally farmed plots in the RADE gave rise to the hypothesis that the rotational grazing system typically found in New Zealand agriculture is operating at a near optimum and cannot be compared to most livestock or cropping systems within other countries. However, further research is required to determine if regenerative systems could provide a higher level of yield stability for high-stress environments, such as the drought prone east coast region of New Zealand. Furthermore, there are opportunities for research on animal performance, soil carbon sequestration and on the long term implications of these multispecies regeneratively managed pastures.