Post-Pyrolysis Nutrient Enhancement of Wood Biochar with Compost and Uncharred Wastes- Influence on Soil Chemical Properties and Crop Productivity

Abstract

Highly carbonised biochar with desirable characteristics such as high porosity, surface area, mechanical strength, and others is attainable at higher highest treatment temperatures (HTTs). Conversely, however, at these higher temperatures, the availability of most plant nutrients reduces. It is therefore vital to nutritionally enrich such biochar for the betterment of crop growth and development. In this study, we employed two different biochar nutrient enhancement strategies. In one approach, oak biochar pyrolysed at higher HTTs of 600°C was combined with livestock compost in a ratio of 1: 4 (biochar: compost). The second strategy involved pelletizing a mixture containing 30% of the biochar mentioned above, 50% of nitrogen-rich castor meal, 10% spent coffee grounds and 10% rice bran (binding material). These two improved biochar fertilisers were then evaluated for their efficiencies in improving soil chemical properties and supporting the growth and development of eggplants through a pot experiment that lasted for a single growing season. Also tested were the effects of combined applications of the nutrient-enhanced biochar fertilisers (EBF) and NPK. The results indicate that both enhancement strategies positively influence biochar's ability to improve soil chemical properties, although the influence on agronomic performance was mostly negative. Such enhanced biochar fertilisers should, therefore, be applied to the soil in combination with mineral fertilisers if excellent benefits accruing from their usage are to be realised.