Abstract
The role of extractable pool of biochar in crop productivity and soil greenhouse gas (GHGs) emission is not yet clear. In this study, two biochars with and without extraction was added to a paddy before rice transplantation at 20 t·ha−1. Crop yield, plant traits and greenhouse gas emission monitored throughout a rice-wheat rotation. Between the biochar treatments, changes in bulk density and microbial biomass carbon were insignificant. However, the increase in organic carbon was similar between maize and wheat biochars while higher under bulk wheat biochar than extracted one. The increase in available P and K was higher under wheat than maize biochar regardless of extraction. Moreover, the increase in plant traits and grain yield, in rice season only, was higher under bulk than extracted biochars. Yet, there was no difference in changes in GHGs emission between bulk and extracted biochars regardless of feedstock. Nevertheless, increased methane emission for rice season was lower under extracted biochars than bulk ones. Overall, crop productivity rather than GHGs emission was affected by treatment of extraction of biochars. Thus, use of unextracted biochar is recommended for improving soil crop productivity in the paddy soils.
Highlights
The agricultural soils and fragile soils with low resilience are at risk of degradation and ecosystem failure under climate change and crop production intensification[1,2]
We hypothesize that: firstly, extraction of biochar with removal of some extractable OC fractions and water soluble nutrients would modify biochar’s role in supplementing organic/inorganic nutrients and in promoting crop growth; Secondly, such extraction could affect biochar’s role in improving soil OC stock and as well as in reducing soil respiration and greenhouse gas (GHGs) such as methane emission from rice paddy; Thirdly, the extraction induced change in the above effects could last shortly as rice is cultivated under seasonally flooding condition and such effects would differ between different biochars containing different size and composition of a water extractable portion
Through a comparative study of a rice paddy across a whole cycle of rice-wheat rotation, we aimed to address if a water extractable pool of biochar affects soil physico-chemical properties, crop traits and yield, and soil respiration and greenhouse gas emissions and if these changes differ between types of biochar, and time span of the rice-wheat rotation system
Summary
The agricultural soils and fragile soils with low resilience are at risk of degradation and ecosystem failure under climate change and crop production intensification[1,2]. Through a comparative study of a rice paddy across a whole cycle of rice-wheat rotation, we aimed to address if a water extractable pool of biochar affects soil physico-chemical properties, crop traits and yield, and soil respiration and greenhouse gas emissions and if these changes differ between types of biochar, and time span of the rice-wheat rotation system. This information would be of critical value for developing biochar products for enhancing crop productivity and climate stabilization in rice agriculture
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