Is Black Gold the Saviour for NZ Agriculture? - Dr Gordon Rajendram on the Promise of Biochar and Humates
Introduction
New Zealand farmers often face two major challenges: nutrient loss from soils and the impacts of dry conditions. Dr Gordon Rajendram says solid humates and biochar, both derived from plant-based materials, can be valuable tools in addressing these issues. Used in soils or as part of animal feed, they help retain water and nutrients where they are needed most [1].
"The key is getting more value from every drop of water and every kilogram of fertiliser," says Dr Rajendram. "Humates and biochar work with nature to do exactly that."
Humates: Feeding Soil and Livestock
Humates are rich in humic and fulvic acids, typically sourced from lignite (brown coal) [2]. With a naturally high cation exchange capacity (CEC), they hold onto water and nutrients, keeping them available to plant roots [3]. By binding with nitrogen compounds, humates can reduce nitrate leaching, one of the biggest environmental issues facing New Zealand’s pastoral farming systems. They also limit nitrous oxide emissions, a potent greenhouse gas, by locking nitrogen into the soil.
Humates stimulate beneficial soil microbes and improve soil structure. When included in livestock feed, they aid digestion, boost mineral uptake, support immunity, and help control parasites [4]. Healthier stock means better performance in the paddock and higher-quality manure returning to the soil.
Biochar: Long-Lasting Benefits for the Land
Biochar is charcoal made from wood or crop residues in a low-oxygen environment [5]. Like humates, it has a high CEC and acts as a reservoir for nutrients and moisture. The Australia New Zealand Biochar Industry Group (ANZBIC) highlights its ability to build long-lasting soil carbon, reduce nitrate leaching, and retain nitrogen in the soil [6]. This reduces both nutrient losses to waterways and nitrous oxide emissions, tackling two of the most pressing environmental concerns for NZ agriculture.
When incorporated into compost or seedbeds, biochar improves soil resilience, helping pastures survive dry conditions [7]. In small amounts, it can also be added to feed, where it binds toxins, improves gut health, and enhances manure quality [8].
Is Black Gold the Saviour?
There is growing evidence that biochar, sometimes called “black gold”, can be a game-changer for worn-out soils. While not a standalone solution, used alongside balanced nutrition and good farming practice, it strengthens soil structure, builds fertility, and reduces environmental impacts [9].
Conclusion
Dr Gordon Rajendram believes that solid humates and biochar offer practical, proven benefits for Kiwi farmers. By reducing nitrate leaching, lowering nitrous oxide emissions, and improving nutrient and water efficiency, they support stronger pastures, healthier animals, and more sustainable farming for the future.
Key References
[1] Lehmann, J., & Joseph, S. (2015). Biochar for Environmental Management. Routledge. https://doi.org/10.4324/9780203762264
[2] Stevenson, F.J. (1994). Humus Chemistry. Wiley. https://www.wiley.com/en-us/Humus+Chemistry-p-9780471594741
[3] Khan, S.A. et al. (2007). "The Myth of Nitrogen Fertilization for Soil Carbon Sequestration". Journal of Environmental Quality. https://doi.org/10.2134/jeq2007.0099
[4] Islam, K.M.S. et al. (2005). "Use of Humic Substances in Agriculture". Pakistan Journal of Nutrition. https://doi.org/10.3923/pjn.2005.126.134
[5] International Biochar Initiative. (2023). Biochar Basics. https://biochar-international.org/biochar/
[6] Australia New Zealand Biochar Industry Group (ANZBIC). (2024). Biochar and Soil Health. https://www.biochar.net.nz/
[7] Schmidt, H.P. et al. (2019). "Biochar in Animal Husbandry". Agriculture. https://doi.org/10.3390/agriculture9040081
[8] Glaser, B. et al. (2002). "Ameliorating Physical and Chemical Properties of Highly Weathered Soils". Biology and Fertility of Soils. https://doi.org/10.1007/s00374-002-0466-4
[9] Jeffery, S. et al. (2011). "A Quantitative Review of the Effects of Biochar on Soil Properties". Agriculture, Ecosystems & Environment. https://doi.org/10.1016/j.agee.2010.09.011
Contact Dr Gordon Rajendram
rajendram@xtra.co.nz
021 466 077
https://gordonrajendramsoilscientist.co.nz/
Contact MediaPA
027 458 7724
phillip@mediapa.co.nz