Biochar Effects on Nutrients Retention and Release of Hydroponics Growth Media

Applying biochar (BC) to broad acre crops is an effective way to sequester carbon while improving soil fertility and reducing nutrient leaching. Adopting a similar approach in a hydroponic environment, BC may enhance nutrient availability and reduce natural fluctuations in the nutrient solution. This study monitored the effect of BC addition to peatmoss growth media with ratios of 0%, 5%, 25% and 50% on pH, electrical conductivity (EC) and macronutrient retention, over 15 days using hydroponic nutrient solution controls. Deionised water was used to measure nutrient releases in the closed loop hydroponic system, showing that biochar increased pH level in both retention and release stages. As expected, the pH increased by a maximum of 1.5 units with the highest biochar to growth media ratio due to the natural liming nature of the BC. The EC was also affected, as BC increased in the media EC reduced. With regards to retention of nutrients, BC recovered nitrate, phosphate, calcium and sulphate but did not affect magnesium. Potassium levels increased in solution with increasing BC ratio. In terms of outcomes relevant to global agriculture, the results show that the same level of production can nominally be obtained with around half the nutrient requirements.