Search

Improving nitrogen (N) use efficiency (NUE) in crop plants is important to reduce the negative impact of excessive N on the environment. Although biochar‐blended fertilizer had been increasingly tested in crop production, the fate of fertilized N in soil and plant had not been elucidated in field conditions. In this study, a novel biochar‐blended urea (BU) was prepared by pelleting maize straw biochar, bentonite, sepiolite, carboxymethylcellulose sodium, and chitosan with urea (commercial urea without biochar [CU]). N fertilization in a winter wheat field was treated with BU and CU at both 265 kg N ha−1 (HL) and 186 kg N ha−1 (LN). Within a treatment plot, a microplot was fertilized with 15N‐labeled urea at a relevant N level. We investigated the influence of fertilizer management on biomass, grain yield, bioaccumulation of nutrient, soil properties, 15N isotopic abundance, and greenhouse gas emissions. Microscopic and spectroscopic analysis showed that micro/nanonetwork of biochar could bind N to form a loss control agglomerated particle, and organo‐mineral coatings on BU may protect N from quick release. Compared with CU, BU significantly increased grain yield by 13% and 38%, and grain N allocation by 19% and 55%, respectively, at HN and LN level. The total recovery of urea 15N in wheat plant (15N based NUE) was 32.8% under CU regardless of N rates but increased to 41.7% (HN rate) and 56.3% (LN rate) under BU. Whereas, the soil proportion (soil residual 15N) was 20.1% and 13.4% under CU but 32.5% and 18.8% under BU, in 0‐20cm topsoil, respectively, at HN and LN rate. Compared with the CU, BU had no effect on CO2 and CH4 emissions but significantly reduced the total N2O emission by 23%–28%. These important findings suggested that BU can be beneficial to uplift plant NUE to reduce reactive N loading but boost crop production. [ABSTRACT FROM AUTHOR]

Aims: Although elevated atmospheric CO2 and global warming are important climate factors that affect soil carbon sequestration and greenhouse gases emission from agricultural soils, it remains unclear how these factors affect the soil microbial communities that involved in nitrous oxide (N2O) emission. The objectives of this study were to evaluate the interactive effects of elevated CO2 and warming on soil microbial community and its relationship with soil N2O emission. Methods: Soil N2O emission was monitored in a Free-Air CO2 Enrichment facility equipped with warming during wheat growth season. The abundance and community composition of ammonia-oxidizing bacteria (AOB) and archaea (AOA) and denitrifiers (nirK, nirS and nosZ) in the rhizosphere were determined using real-time PCR and Illumina MiSeq sequencing technique. Results: Elevated CO2 increased N2O emission, the abundance of AOB and nirK, the concentration of rhizospheric soil organic carbon (SOC) and total nitrogen (TN); while it decreased the concentration of soil available phosphorus and potassium. Warming decreased soil pH, and the abundance of AOB, nirK and nosZ; and the effect of warming on soil N2O emission, SOC, TN and AOB abundance was significantly interacted with elevated CO2. Under elevated CO2, warming decreased soil N2O emission but increased the concentration of rhizosphere SOC and TN. Pyrosequencing showed that AOB, nirK, and nosZ community compositions were altered by elevated CO2 levels, and redundancy analyses further showed that variations in SOC, TN and pH determined these community compositions. Soil N2O emission was positively corelated with soil pH, the content of SOC and nitrate, and the abundance of AOB and nirK. Conclusions: Our results demonstrated that future climate change of elevated CO2 plus warming will not lead to a significant increase in agricultural soil N2O emission. Ammonia oxidizer (AOB) and denitrifier (nirK) are the key soil microbial community that regulate the response of soil N2O emission to elevated CO2 and warming. [ABSTRACT FROM AUTHOR]

Summary: Biochar amendment has been proposed as a promising means to increase carbon (C) sequestration and simultaneously benefit plant productivity. However, quantifying the assimilation and dynamics of photosynthetic C in plant–soil systems under biochar addition remains elusive.This study established two experimental factors involving biochar addition and nitrogen (N) fertilization to quantitatively assess the effect of biochar on photosynthetic C fate in a rice plant–soil system. The rice plants and soil samples were collected and analyzed after 6‐h pulse labeling with 13CO2 at the tillering, jointing, heading and ripening stages.Biochar did not affect the proportions of photoassimilated carbon‐13 (13C) allocations in plant–soil systems. Nevertheless, biochar enhanced the 13C contents in the shoot, root, and soil pools, especially when combined with N fertilization, and biochar increased the cumulative assimilated 13C contents in the shoot, root, and soil pools by 23%, 14% and 20%, respectively, throughout the whole growth stage. Moreover, biochar addition significantly enhanced the N use efficiency (NUE) by c. 23% at the heading and ripening stages.In summary, biochar increases the content of photoassimilated C in plant–soil systems by improving plant productivity via enhancing NUE, thus resulting in a higher soil C sequestration potential. [ABSTRACT FROM AUTHOR]