Stover and biochar can improve soil microbial necromass carbon, and enzymatic transformation at the genetic level

Abstract

To understand how stover incorporation affects the levels of soil carbon and its biogeochemistry process, we examined soil carbon and amino sugar carbon (AS‐C). Activity of N‐acetylglucosaminidase (NAGase) and the abundance (real‐time quantitative polymerase chain reaction, RT‐qPCR) and communities of the bacterial chitinase‐encoding gene (chiA) were monitored. We implemented a maize cropping system, which included four treatments, i.e., chopped maize stover returned directly (SD), compost produced by maize stover (SC), biochar produced by maize stover (BC), and stover removal (CK). The results showed that BC and SD enhanced soil organic carbon (SOC), microbial biomass carbon:SOC, total AS‐C, glucosamine carbon, galactosamine carbon, NAGase activity, and chiA gene abundance significantly. There were significant positive correlations between the abundance of the soil chiA gene and NAGase activity. Biochar and stover treatments increased the number of total operational taxonomic units (OTUs), unique OTUs, and the chao 1 and ACE richness indices, but decreased the Shannon and Simpson diversity indices. The dominant chiA‐harboring bacterial phyla were Actinobacteria, Proteobacteria, and Bacteroidetes. Some detectable genera in Actinobacteria had high relative abundance, including Streptomyces, Actinoplanes, and Amycolatopsis. PLS‐DA and CCoA revealed that the chiA community in the BC or SD plots was significantly different from that in the CK plots, and differences between BC and SD were not significant. Similar soil properties, diversity, and the abundance of chiA were observed between SC and CK. Greater abundance and diversity of the chiA gene with BC incorporation were associated with higher pH, SOC, and TN concentration. Soil pH was related to the composition and abundances of the chiA‐harboring microbial communities (CCA).

Maize straw is more effective than maize straw biochar at improving soil N availability and gross N transformation rate

“…Partially agreeing with our hypothesis, we found that the gross N mineralisation rate in ST was significantly higher than that in CK from July to October, and the seasonal cumulative gross N mineralisation also far exceeded that in CK and BC (Table 3). The potential mechanisms may be related to successive straw return, which improved the soil organic N content (Table 2), especially the easily decomposable organic N that is readily available for mineralisation (Ren et al, 2023; Yuan et al, 2022; Zhang et al, 2022), and therefore, increased the gross N mineralisation rate under the high soil moisture and temperature conditions prevailing in mid‐summer (Figure S2); however, even biochar also had higher soil total N content than CK (Table 2), but biochar did not increase the gross N mineralisation rate on any labelling date or on a seasonal scale. This was because even the majority of plant N was maintained during the pyrolysis process, but those occurring in heterocyclic compounds (Kazi et al, 2011), and were generally considered those organic N, like biochar C, is recalcitrant and cannot be easily metabolized or assimilated by the soil microbial community or by plants (Cantrell et al, 2012; Prommer et al, 2014).…”

“…This explained why biochar failed to stimulate bacterial and fungal growth in this study. In contrast, straw application increased bacterial and fungal abundance, implying that long‐term straw amendment may be more effective than biochar in improving soil biological fertility (Xu et al, 2019; Zhang et al, 2022).…”

“…This explained why biochar failed to stimulate bacterial and fungal growth in this study. In contrast, straw application increased bacterial and fungal abundance, implying that long-term straw amendment may be more effective than biochar in improving soil biological fertility (Xu et al, 2019;Zhang et al, 2022). AOB and AOA are ammonia-oxidising microbes that implement ammonia oxidation, and our results showed that the AOB-amoA gene outnumbered the AOA-amoA gene, which is in agreement with numerous results showing that AOB-amoA functionally dominated ammonia oxidation in neutral and alkaline environments (Meinhardt et al, 2018), particularly in NH 4 þ -N fertilized agricultural soils (Ouyang et al, 2018).…”

Microbial community and network differently reshaped by crushed straw or biochar incorporation and associated with nitrogen fertilizer level

“…After collection, soil samples were then mixed, sieved, and divided into the following two parts: microbial (stored at −80°C) and soil properties (air-dried at room temperature) analyses. Soil properties, including total nitrogen (TN), total carbon (TC), NH 4 + -N (AN), available phosphorus (AP), available potassium (AK), soil organic carbon (SOC), pH, water content (WC), and bulk density (BD), were determined in accordance with our previous work (Zhang et al, 2022).…”

Biochar and Microplastics Affect Microbial Necromass Accumulation and CO2 and N2O Emissions from Soil

“…The introduction of engineered C materials (e.g., BC and microplastics) inevitably influences the composition and stability of the soil C pools. Typically, a single application of BC increases MNC accumulation by 10–20%, − whereas multiple BC applications over a decade-long time frame have been reported to increase MNC by 21–59% . However, some studies have reported a decrease in amino sugar and MNC contents following BC addition.…”