Phytostabalization of the heavy metals in the soil with biochar applications, the impact on chlorophyll, carotene, soil fertility and tomato crop yield

Food crops cultivation on the contaminated soil is a health concerning issue that requires effective solution. This study, reports the application of different particle size biochar for reducing heavy metals effect on the crops yield and the soil quality. Pots were filled soil and were treated with biochar <3, 3–6 and 6–9 mm particle sizes. Heavy metals (Cd, Pb, Ni) were spiked and the tomato seedlings were transplanted. The <3 mm biochar significantly (p < 0.05) improved plant height, fresh and dry weight, flowers and fruits plant−1 and fruits yield by 32, 50, 33, 57, 35 and 69% compare to the control and by 22, 17, 24, 16, 30 and 48% to the 6–9 mm particle sized biochar, respectively. The <3 mm particles showed significant and maximum improvement in the chlorophyll a, b, total chlorophyll, carotene, soil mineral N, AB-DTPA extractable (P and K), soil organic matter, pH(1.5) and soil EC(1.5) by 10, 45, 17, 15, 100, 29, 30, 2, 1 and 12%, respectively. Soil bulk density was reduced while the soil saturation and porosity were found to increase. Amongst the heavy metals maximum reduction in plant height (30%), fresh weight (25%), dry weight (26%) and flowers plant−1 (38%) was noted with Ni contamination, while the Pb hazard was found maximum on fruits plant−1 (72%) and fruit yield (47%). Reduction in the chlorophyll a, b, total chlorophyll and carotene was also found maximum under Ni contamination (19, 52, 29 and 26%) than the Pb (1, 20, 0.2 and 4%) and Cd (1, 18, 3 and 4%) respectively. The soil organic matter in Pb, Cd and Ni contamination was lowered by 96, 22, 41%, the bulk density was found higher by 1.5, 1, 2%. The porosity and mineral N were also found lower. It was concluded that lower size biochar particles were significantly more effective for potential agronomic and soil fertility benefits of biochar under contaminated soil conditions.