Corn crop can sequester 34 tonnes CO2-e per hectare per year (DI&I)

Corn can be used to build soil carbon levels. Total carbon added from corn roots averaged five tonnes per hectare per year with cotton-corn and 9.3t/ha/year with back-to-back corn, says Industry & Investment NSW senior research scientist, Nilantha Hulugalle. THIS IS THE EQUIVALENT OF BETWEEN 18 TONNES OF CO2-E AND 34 TONNES OF CO2-E PER HECTARE PER YEAR. Soil organic carbon dynamics in these farming systems have focussed on inputs of above-ground material.
“Addition of root material to soil carbon stocks either in the form of roots dying and decaying during and after the crop’s growing season are, however, significant," she said in a Land Newspaper report.
A project examining grey clay cotton soils near Narrabri found root death and decay contributed more than half of corn’s carbon to soil. Corn is a summer crop often grown under irrigation after cotton.
“We measured corn root growth in back-to-back corn and a cotton-corn rotation sown on one metre beds during the summers of 2007-08 and 2008-09, Dr Hulugalle said. Root measurements were made at intervals of two to four weeks during the growing season by using a combination of soil cores, a minirhizotron and an image capture system, using a video camera inserted into the soil through a clear plastic root observation tube. “The video camera was connected to a field computer with software which is able to take root images at specified depths. Carbon was analysed in roots sampled by coring.
The amount of carbon held in the crop roots at the end of the season and the amount of carbon added to the soil by roots dying during the growing season, were measured. Corn root densities, particularly towards the latter part of the growing season, were higher with back-to-back corn than with cotton-corn rotation.
“The amount contributed by root death during the growing season averaged 11% of the total amount.
“Relative to carbon contributed by the whole corn crop, above and below the ground, the amount of carbon contributed by roots can range from 50% to 65%.”