Sarah Hoppen

Research overview

The interval between defoliations is one of the factors with the greatest impact on the nutritive value and persistence of pastures; influences the efficiency of the plant in converting light, water and nutrients in photosynthetically active tissue and organic reserves. The objective of this research was to quantify the effects of defoliation interval (28, 42 or 84 days) on three fall dormancy levels of alfalfa (FD2, FD5 or FD10) over five years. Dormancy levels were selected for their physiological differences in root reserves in response to external factors. While the defoliation regimes were intended to cause different levels of stress in the plants. The study was developed in the experimental area of Lincoln University, in the region from Canterbury, New Zealand, between February 2015 and April 2019. Results showed FD2 and FD5 had greater partitioning capacity of organic components to the roots, resulting in the increase of biomass of this organ and greater absorption of water and nutrients, which led to greater support energy for rapid canopy expansion. The carbon limitation was accompanied by limitation of nitrogen (N), associated with low availability of water and reduced root development. It is concluded that the FD2 managed under a 42 day rotation was the most suitable combination for the Canterbury region, being more efficient in the capture, use and partitioning of N and water. Sarah was supervised by supervised by Dr Marcela Abbado Neres (Universidad Estadual Do Oeste Do Parana) and Professor Derrick Moot (Lincoln University).