Grape marc biochar as a soil amendment: Potential for improving soil fertility, vine nutrition, and carbon sequestration: A thesis submitted in partial fulfilment of the requirements for the Degree of Master of Science at Lincoln University

Agricultural activities generate large volumes of biowaste that can pose significant environmental challenges if poorly managed. In viticulture, grape marc is a major by-product, and inappropriate disposal can contribute to soil and water contamination, air pollution, and greenhouse gas emissions. Converting such residues into soil amendments represents a promising strategy to enhance soil fertility while mitigating environmental impacts. This study evaluated the potential of biochar (BC) produced from grape marc as a soil amendment to enhance soil fertility, improve vine performance, and increase soil carbon sequestration in vineyard systems. The effects of pyrolysed grape marc biochar (GM-BC) on soil properties and grape vine nutrition were examined through a combination of laboratory incubation and a greenhouse pot trial, using two contrasting soils: a Pallic silty loam and a Typic Fluvial Recent sandy loam, collected from Marlborough, New Zealand’s dominant grape-growing region. In the laboratory incubation, GM-BC (20 and 40 t ha⁻¹ ), grape marc compost (GM-Com; 40 t ha⁻¹), and a 1:1 (w/w) biochar-compost mixture (MIX; 40 t ha⁻¹) were applied to the two soils and incubated for seven months at 20 °C, during which soil physical and chemical characteristics were measured regularly. The greenhouse trial tested GM-BC at the two rates in the two soils and also looked at their effects on grape vine vegetative growth and nutrient uptake under well-irrigated and deficit irrigation conditions. In the incubation trial, the amendment incorporation improved soil fertility by significantly increasing soil pH, total C (TC), total N (TN), available P, exchangeable K⁺, cation exchange capacity (CEC), water holding capacity (WHC), and aggregate stability. Soil total carbon concentrations increased by 35.4% in the Pallic soil and 23.4% in the Recent soil, while plant-available P concentrations increased by 11.4% and 29.9%, respectively. The greatest improvements in soil physical properties were generally observed in the coarse-textured Recent soil, with a 12.8 % improvement in WHC at −100 kPa, while a smaller increase of 8.9% in the Pallic soil was also significant. Both GM-BC and GM-Com applications substantially increased the recalcitrant soil C pool, with C sequestration increasing with BC application rate. The carbon sequestration potential of GM-BC was quantified from the incubation experiment results and, when combined with survey-derived data, showed that the highest C mitigation potential occurred at the BC application rate of 40 t ha⁻¹. A scenario analysis of potential C offsets revealed that the greatest benefits were achieved in the Pallic soil at 20 t ha⁻¹ and in the Recent soil at 40 t ha⁻¹. Biochar application improved vine nutrient status, particularly petiole P and K concentrations, with stronger responses in the Recent soil and the greatest increases under BC20. However, BC had no effect on vegetative growth. Water treatment significantly affected vine growth and water status. Deficit irrigation reduced vine growth, biomass, stomatal conductance (gₛ), and net photosynthesis (Aₙ), while increasing C isotope (δ¹³C), indicating greater water stress. These effects were more pronounced in the Recent soil, and no significant BC x water interactions were observed for vegetative growth parameters. Overall, this study demonstrated that applying GM-BC to vineyard soils enhanced soil fertility and vine nutrient uptake while contributing to measurable C sequestration. The findings suggest that GM-BC is a promising soil amendment and carbon sequestration material, although long-term field studies are required to confirm the persistence and scalability of its effects.

Grantor dc:publisher

Lincoln University

Year dc:date

2026

Author dc:creator

• Dang, Diep Yen Huong

• grape marc
• biochar
• soil amendment
• soil nutrients
• vine growth
• soil sequestration
• carbon footprint
• ANZSRC::410604 Soil chemistry and soil carbon sequestration (excl. carbon sequestration science)
• ANZSRC::300805 Oenology and viticulture
• ANZSRC::410601 Land capability and soil productivity

Licence

• https://researcharchive.lincoln.ac.nz/pages/rights

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/10182/20896

OAI identifier oai:identifier

oai:researcharchive.lincoln.ac.nz:10182/20896