Biochar amended compost maturity evaluation using commercial vegetable crops seedlings through phytotoxicity germination bioassay

Abstract

Objectives: Phytotoxicity is a significant indicator of final compost product maturity and is assessed through germination bioassays using a variety of crop seeds. In this study, the final composted product extracts from a mixture of different raw materials, such as swine manure (SM), biochar (BC), and sawdust (SD) were examined for their phytotoxic effects on five different commercial vegetable crop seeds. Methods: The final composted products were procured by applying four different treatments (i.e., SM + SD + 3%BC (T1), SM:SD + 5%BC (T2), SM:SD + 10%BC (T3), and SM:SD (C) used as a control (without nanobiochar). The effect of phytotoxicity on vegetable crop seed growth was measured using GI% (germination index), RSG% (relative seed germination), and RRE% (relative root elongation) in five commercial crops, including radish (Raphanus sativus), carrot (Daucus carota), cabbage (Brassica oleracea), tomato (Lycopersicon esculentum), and napa cabbage (Brassica rapa). Results: In accordance with the phytotoxicity results, none of the treatment compost product extracts had any phytotoxic effect on the five commercial crop seeds, which agreed with our previous study on final product nutrient availability and manure maturity. Moreover, T3 (10% BC) showed the highest GI value compared to the other treatments, including the control. Conclusions: Overall, the results confirmed that compost extract, especially 10% biochar amendment, was beneficial for commercial vegetable crops.

Keywords

• Compost manure
• Nutrient quality
• Crop seeds
• Phytotoxic effect
• Germination index