TECHNICAL
ENHANCING CROP PRODUCTIVITY WITH BIOCHAR TECHNOLOGY Words by Neha Jha (Massey University), Jessica Lunsford (Lincoln University), Nick Roskruge (Massey University), Leo Condron (Lincoln University), Marta Camps (Massey University) and Sally Anderson (Onions NZ)
Biochar is charcoal that is produced by pyrolysis of biomass in the absence of oxygen. It is used as a soil ameliorant for both carbon sequestration and soil health benefits
Soil scientists from Massey and Lincoln Universities are collaborating with Onions New Zealand to enhance crop productivity in the Pukekohe region. Soils of the Pukekohe region are considered highly versatile 'high-class soils' for growing a wide range of crops due to their fertility properties, combined with favourable climatic conditions for year-round supply. The Pukekohe region is a hub to essential transport routes, supplying vegetables to Auckland, the largest and fastestgrowing region. Onions are the highest vegetable export earner for New Zealand, and the demand is increasing each year. Preservation and enhancement of high-class soils is critical for future farming in this region, given the land use capability of these soils and the increase in production volume. Driven by the pressures of urban expansion and the reduction of available prime growing land, intensification of farming practices has increased in the region. Intensification increases the potential to reduce crop performance, in addition to diminishing soil and water quality. One of the key indicators of soil quality is the organic carbon content of the soil. Soil organic carbon is critical in the provision of several soil functions: biomass 40 NZGROWER : AUGUST 2021
and food production, maintaining soil biodiversity, carbon sequestration, nutrient storage and cycling, and water filtration and transformation. Intensification of crop production has led to a drop in soil organic carbon stocks in Pukekohe soils (from around 55–65 g C kg-1 to 15–20 g C kg-1) after 60 to 80 years. Consequently, there is a rising interest in improving soil organic carbon stocks for agricultural and horticultural soils.
Onions are the highest vegetable export earner for New Zealand Sustainable soil management practices can reverse the impacts of soil organic carbon losses. Biochar amendments are proposed as an innovative technology for achieving multiple sustainable soil use and management goals. Biochar is a charcoal-like product produced when waste biomass has undergone thermal treatment with little or no oxygen – a process termed pyrolysis. The conversion of biomass into biochar rapidly locks up a fraction of the carbon present in the original feedstock into a form of carbon that can remain in soils for hundreds to thousands of years. Converting biomass into biochar can sequester atmospheric carbon in terrestrial systems to offset
