Potassium response to wheat straw biochar
Background
In 2015 we applied and were successful in a funding application to the Northern Agricultural Catchments Council (NACC) to run a trial looking at potassium response to applications of wheat straw biochar.
Objectives
Many farmers burn crop residue to control chemical resistant weeds. This is a resource going up in smoke and farmers have the opportunity to capture this residue to produce bioenergy and biofuels. To achieve this outcome, it is important to understand how the by-products of the bioenergy process, like biochar will affect our cropping systems.
Farmers on soil types low in potassium import Muriate of Potash (MOP) to use in wheat crops. Since wheat straw has Potassium, we wanted to ask the question, is there potential to mine Potassium from soil types typically high in potassium, process the straw through pyrolysis to produce bioenergy and biochar and use the biochar to replace potassium in a cropping regime?
Outcomes
It was a difficult year to run a trial of this nature. The early timing of seeding combined with a dry spell in the first half of the season reduced the potential of the crop significantly. Due to this yield decrease, there were enough nutrients in the soil to maintain a crop of this potential, so it was difficult to determine any significant variation in treatments.
Treatment 11 – 100kg of wheat straw biochar + 110kg of Agras was the highest yielding biochar/fertiliser treatment which yielded 1.56t/ha. Treatment 4 – 55kg of Ktill plus and 35kg of biochar yielded 1.53t/ha
The fact that half rates of fertiliser plus a low rate of biochar returned the highest gross margin (apart from the control) and consistent yield (1.53t/ha) is encouraging and should be explored further.
For further information please see the final report NACC Demonstration Final Report.
