The sustainable management of leftover rice straw through biochar production to mitigate CH₄ emissions and enhance rice yield remains uncertain and undefined. Therefore, we evaluated the effects of using biochar derived from rice straw left on fields after harvest on greenhouse gas emissions, global warming potential (GWP), and rice yield in the paddy field. The experiment included three treatments: chemical fertilizer (CF), rice straw (RS, 10 t ha⁻¹) + CF, and rice straw-derived biochar (BC, 3 t ha⁻¹ based on the amount of product remaining after pyrolysis) + CF. Compared with CF, BC + CF significantly reduced cumulative CH₄ and CO₂ emissions, net GWP, and greenhouse gas emission intensity by 42.9%, 37.4%, 39.5%, and 67.8%, respectively. In contrast, RS + CF significantly increased cumulative CH₄ emissions and net GWP by 119.3% and 13.8%, respectively. The reduced CH₄ emissions were mainly caused by the addition of BC + CF, which did not increase the levels of dissolved organic carbon and microbial biomass carbon, consequently resulting in reduced archaeal abundance, unlike those observed in RS + CF. The BC + CF also enhanced soil total organic carbon content and rice grain yield. This study indicated that using biochar derived from leftover rice straw mitigates greenhouse gas emissions and improves rice productivity in tropical paddy soil.

Little is known about the carbonaceous greenhouse gases and soil microbial community linked to the combination of biochar (BC) and rice straw (RS) in paddy soils. The objectives of this research were to evaluate the effects of combining BC and RS on (1) CH₄ and CO₂ production from paddy soil, (2) archaeal and bacterial abundance, and (3) rice grain yield. The experiments consisted of a pot trial and an incubation trial, which had a completely randomized design. The experiments included five treatments with three replications: (a) the control (without BC, RS, and chemical fertilizer (CF)); (b) CF; (c) BC 12.50 t ha⁻¹; (d) RS 12.50 t ha⁻¹; and (e) combined BC 6.25 t ha⁻¹ + RS 6.25 t ha⁻¹ + CF. In the sole RS treatment, CH₄ production (0.0347 mg m⁻² season⁻¹) and the archaeal and bacterial abundance (5.81 × 10⁸ and 4.94 × 10¹⁰ copies g⁻¹ soil dry weight (DW)) were higher than outcomes in the sole BC treatment (i.e., 0.0233 mg m⁻² season⁻¹ for CH₄ production, and 8.51 × 10⁷ and 1.76 × 10¹⁰ copies g⁻¹ soil DW for archaeal and bacterial abundance, respectively). CH₄ production (0.0235 mg m⁻² season⁻¹) decreased significantly in the combined BC + RS + CF treated soil compared to the soil treated with RS alone, indicating that BC lessened CH₄ production via CH₄ adsorption, methanogenic activity inhibition, and microbial CH₄ oxidation through bacterial methanotrophs. However, the archaeal abundance (3.79–5.81 × 10⁸ copies g⁻¹ soil DW) and bacterial abundance (4.94–5.82 × 10¹⁰ copies g⁻¹ soil DW) in the combined BC+ RS + CF treated soil and the RS treated soil were found to increase relative to the treatments without RS. The increase was due to the easily decomposable RS and the volatile matter (VM) constituent of the BC. Nevertheless, the resultant CO₂ production was relatively similar amongst the BC, RS, and BC + RS treated soils, which was indicative of several processes, e.g., the CO₂ production and reduction that occurred simultaneously but in different directions. Moreover, the highest yield of rice grains was obtained from a combined BC + RS + CF treated soil and it was 53.47 g pot⁻¹ (8.48 t ha⁻¹). Over time, the addition of BC to RS soil enhanced the archaeal and bacterial abundance, thereby improving yields and reducing CH₄ emissions.

Rice straw (RS), a major agricultural byproduct in Thailand, holds significant potential for biochar production. This study investigated the physicochemical properties, pore structure, and yield of rice straw-derived biochar (RSBC) produced using a traditional drum kiln, compared to raw RS. Synchrotron-based X-ray tomographic microscopy (XTM) was employed to characterize changes in pore type, size, and volume. The pyrolysis of RS resulted in a 70% mass reduction; however, RSBC exhibited significantly higher fixed carbon content, cation exchange capacity (CEC), and water-holding capacity (WHC), attributed to increased aromatic functional groups following lignin enrichment and the decomposition of cellulose and hemicellulose. Synchrotron-based XTM analysis revealed an 18% increase in total porosity, driven by a 19% rise in open-pore porosity and a 91% reduction in closed-pore porosity. Additionally, macropore volume (> 100 μm) expanded by 271%, leading to a 267% increase in total pore volume. These structural modifications, particularly the enhanced open-pore porosity and macropore expansion, along with the formation of aromatic and phenolic functional groups, are key contributors to the improved WHC and CEC observed in RSBC. Overall, these findings highlight the potential of rice straw-derived biochar produced via traditional drum kiln pyrolysis as an effective soil amendment, offering a viable alternative to agricultural waste management in rice cultivation systems.

Leaf litter plays a major role in carbon and nutrient cycling, as well as in fueling food webs. The chemical composition of a leaf may directly and indirectly influence decomposition rates by influencing rates of biological reactions and by influencing the accumulation of soil organic carbon content, respectively. This study aimed to assess the impact of the chemical composition of rubber (Hevea brasiliensis (Willd. ex A. Juss.) Muell. Arg.) leaves on various soil properties of different ages of rubber (4–5, 11–12, and 22–23 year-old). Synchrotron-based Fourier transform infrared microspectroscopy (Sr-FTIR) was utilized for analyzing the chemical composition of plant leaves. The Sr-FTIR bands illustrated that the epidermis of rubber leaves from 4–5-year-old trees was found to contain a high quantity of polysaccharides while mesophyll from 22–23-year-old trees had a large number of polysaccharides. The change in soil properties in the older rubber plantation could be attributed to its chemical composition. The change in soil properties across all tree ages, i.e., increased litter and organic carbon content, was a relatively strong driver of soil biota evolution. The aliphatic of C-H in the leaves showed high correlation with soil organic carbon (SOC) and permanganate-oxidizable C (POXC) from 22–23 year-old trees. This study shows the differences in the organic chemical composition of leaves that are consequential to soil organic carbon.

The objective of this research was to study plant-microbe interactions in rhizospheric soil treated with different quality organic residues in short-term incubation of the soil and subsequent planting of maize crop. The treatments combinations were, 1) untreated soil (control; CT), 2) groundnut stover (GN) with high nitrogen (N) but low lignin (L) and polyphenol (PP), 3) tamarind leaf and petiole litter (TM) with medium N, L and PP, 4) rice straw (RS) with low N, L and PP but high cellulose, 5) GN+TM, 6) GN+RS and 7) TM+RS. Single and mixed residue additions of GN and TM, both high and intermediate quality, resulted in higher soil microbial properties and nutrients than the application of RS as a low quality. Accordingly, the application of the former group increased microbial abundances (i.e., bacteria, archaea, and fungi), elevated the enzymes related to the decomposition of organic residue (i.e., invertase, protease, phenoloxidase and peroxidase activity), and enhanced soil nutrients and plant growth. The results indicated that the chemical compositions (N, L, and PP) of the organic residues amendment are key factors regulating soil microbial abundance and enzyme activity both in after incorporation and after planting. Moreover, bacterial and archaeal abundance, and microbial activities including soil respiration, invertase, protease, and peroxidase activity in the soil after planting higher than those in the soil before planting.