Carbonaceous Greenhouse Gases and Microbial Abundance in Paddy Soil under Combined Biochar and Rice Straw Amendment

Abstract

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.

ACC Deaminase Producing PGPR Bacillus amyloliquefaciens and Agrobacterium fabrum along with Biochar Improve Wheat Productivity under Drought Stress

“…Significant improvements in grain yield, photosynthetic rate, transpiration rate, stomatal conductance chlorophyll a, chlorophyll b and total chlorophyll validated the enhanced functioning of the A. fabrum and B. amyloliquefaciens when applied in combination with BC, as compared to using the same rhizobacteria without BC [25]. Secretion of growth hormone, i.e., IAA by the A. fabrum and B. amyloliquefaciens and greater water holding capacity of BC in addition to ACC-deaminase production are the allied factors responsible for the improvement in wheat growth.…”

“…However, a vital biological approach to combat drought impacts is the soil inoculation of plant growth promoting rhizobacteria (PGPR). The PGPR are frequently reported to efficiently elongate plant roots in the pot [21,22] and mitigate drought impacts in field or greenhouse conditions [23,24], and mobilize the immobile nutrients that lead to significant increases in plant vegetative growth [25] and crop yield [26,27]. PGPR produces ACC deaminase enzyme, which catabolizes stress ethylene through cleavage of ACC into α-ketobutyrate and ammonium ion (NH 4 + ) under drought stress, e.g., [28], thus reducing the level of stress ethylene [29,30].…”

Soil Organic Carbon in Sandy Paddy Fields of Northeast Thailand: A Review

“…Nonetheless, there is a lack of data for many key metal cations, such as Al 3+ and Fe 3+ , that play the role of a cationic bridge between SOC's functional group and clay minerals [88,89]. Furthermore, the position of the field in the region [85] and management practices mainly effect the distinction of exchangeable cations and electrical conductivity, as discussed in previous studies [53,60,69,82,90]. * BD = bulk density (g cm −3 ); SOC = soil organic carbon (g kg −1 ); CEC= cation exchange capacity (cmol kg −1 ); EC = electrical conductivity (dS m −1 ); BS = percent base saturation (%); a (pH 1:5w ), b (pH 1:1w ), and c (pH 1:10 Ca 0.002M ); d (0-15 cm soil depth), e (0-20 cm soil depth), f (0-25 cm soil depth), g (0-30 cm soil depth), h (0-36 cm soil depth), and i (0-40 cm soil depth).…”

“…Meanwhile, the high indigenous SOC content residue application tends to improve the dissolved organic carbon (DOC) composition in the soil. In contrast, the high cellulose residues with low amounts of lignin and polyphenols, likely from rice straw, may negatively affect SOC accumulation [66,69,92]. High cellulose composition in the rice straw leads to low-molecular-weight-DOC production, which has low adsorption affinity.…”

“…Biochar, a C-rich form of charcoal, increases the amounts of stable C components such as lignin and fixed-C in the soil, which slows down the microbial decomposition. Furthermore, the combined BC-RS material application in paddy soil has been found to be more beneficial in improving productivity and reducing GHG emissions [69]. The application of bentonite, volcanic ash locally quarried and used commercially in prawn farming, to significantly improve the structural stability of the soil, which relates to high water-holding capacity, has also been linked to the rate of SOC accumulation [94].…”