Biochar impacts on carbon dioxide, methane emission, and cadmium accumulation in rice from Cd-contaminated soils; A meta-analysis
Abstract
Climate change and cadmium (Cd) contamination pose severe threats to rice production and food security.
Biochar (BC) has emerged as a promising soil amendment for mitigating these challenges. To investigate the BC
effects on paddy soil upon GHG emissions, Cd bioavailability, and its accumulation, a meta-analysis of published
data from 2000 to 2023 was performed. Data Manager 5.3 and GetData plot Digitizer software were used to
obtain and process the data for selected parameters. Our results showed a significant increase of 18% in soil pH
with sewage sludge BC application, while 9% increase in soil organic carbon (SOC) using bamboo chips BC.
There was a significant reduction in soil bulk density (8%), but no significant effects were observed for soil
porosity, except for wheat straw BC which reduced the soil porosity by 6%. Sewage sludge and bamboo chips BC
significantly reduced carbon dioxide (CO2) by 7–8% while municipal biowaste reduced methane (CH4) emissions
by 2%. In the case of heavy metals, sunflower seedshells-derived materials and rice husk BC significantly reduced
the bioavailable Cd in paddy soils by 24% and 12%, respectively. Cd uptake by rice roots was lowered
considerably by the addition of kitchen waste (22%), peanut hulls (21%), and corn cob (15%) based BC. Simi
larly, cotton sticks, kitchen waste, peanut hulls, and rice husk BC restricted Cd translocation from rice roots to
shoots by 22%, 27%, 20%, and 19%, respectively, while sawdust and rice husk-based BC were effective for
reducing Cd accumulation in rice grains by 25% and 13%. Regarding rice yield, cotton sticks-based BC signifi
cantly increased the yield by 37% in Cd-contaminated paddy soil. The meta-analysis demonstrated that BC is an
effective and multi-pronged strategy for sustainable and resilient rice cultivation by lowering greenhouse gas
emissions and Cd accumulation while improving yields under the increasing threat of climate change.