Effect Of Biochar Application Rates Research Articles

Biochar modifies soil physical properties mostly through changes in soil structure rather than through its internal porosity

AbstractBesides its carbon sequestration potential, biochar application generally improves soil physical properties, but the magnitude of its impact and the underlying mechanisms remain debated and depend on soil type, biochar application rate, and age. The objective was therefore to determine the effect of biochar application rate and age on physical properties of agricultural soils in a temperate climate. On a silt loam and a sandy loam soils, we compared the physical properties of fresh biochar (1% and 2% w/w) or century‐old biochar (0.5%–1% w/w; 19th‐century kiln sites)‐enriched soil samples with biochar‐free soil samples. Biochar pore network characteristics were determined using helium pycnometry, mercury intrusion porosimetry, scanning electron microscopy observation, and electron dispersive X‐ray spectrometry, whereas location of biochar particles within soil structure was analyzed using optical microscopy observations. Fresh biochar application decreased bulk density by 16.8% and increased saturated water content by 16.0% and macroporosity by 78.8%. These effects were attributed to soil structure improvement rather than to biochar porosity. Soil type and biochar application rate had a limited impact. In the long‐term, biochar effects were mostly nonsignificant, which might result from its fairly low content in kiln sites and from the clogging of its internal porosity by clay particles. Biochar was thus able to improve some soil physical properties in the short‐term, but these effects could no longer be detected in the very long‐term. Further investigating the time rate of change in soil physical properties over several decades following biochar additions to soil would therefore seem particularly relevant.

Amending biochar affected enzyme activities and nitrogen turnover in Phaeozem and Luvisol

AbstractSoil nitrogen (N) is a vital source of nutrients for maintaining soil fertility and crop production. However, the effect of biochar application rate on the mechanism of organic N transformation and the contribution of enzyme mineralization is still unclear. Therefore, we conducted two 5‐year field experiments in contrasting soils (Phaeozem and Luvisol) with biochar application rate at 0 t hm−2 (CK, 0), 22.5 t hm−2 (D1, 1%), 67.5 t hm−2 (D2, 3%), and 112.5 t hm−2 (D3, 5%) to investigate the potential effects of biochar application rate on soil organic nitrogen (N) turnover and its linkage to enzymatic mineralization in contrasting soil. The results showed that soil organic carbon (SOC) and microbial biomass nitrogen (MBN) contents, microbial biomass carbon to nitrogen ratio (MBC:MBN) and protease activity are significantly influenced by biochar application rate whereas not by soil type. Ammonium nitrogen (NH4+‐N) and nitrate nitrogen (NO3−‐N) contents, and dehydrogenase activity are significantly changed by soil type whereas not by biochar application rate. Based on the redundancy analysis, we found that organic N fractions are associated with MBN, SOC, and protease in Phaeozem, but related to protease activity in Luvisol. Our findings indicate that organic N turnover is not only related to the bioavailability of N but also requires carbon substrates in Phaeozem, whereas the transformation of organic N in Luvisol is dominated by enzymatic mineralization as the relatively low level of bioavailable N.

Contrasting effects of biochar application rate in an alkaline desert cropland soil

Improving water and nutrient retention in desert croplands using soil organic amendments can be a major challenge because organic matter decomposes quickly under irrigated conditions in a hot climate. Biochar—a long-lasting carbon-rich soil organic amendment—has been proposed to improve soil water and nutrient retention, but only by carefully selecting an appropriate application rate. To better understand effects of biochar application rate on soil water and nutrient retention in desert croplands, we set up a mesocosm-scale experiment with biochar added at rates of 0, 19.8, 39.7, 79.4, 119.0, and 158.7 t ha−1 to an alkaline, sandy loam soil. After initial water retention measurements, we added fertilizer and then measured gaseous nitrogen losses as well as soil nitrate (NO3−) and phosphate (PO₄³⁻) leaching. Then, we measured biochar's effect on the soil's capacity to hold plant-available water (i.e., available water capacity, or AWC) using Tempe cells and a dewpoint potentiometer. We found contrasting effects of low and high biochar application rates. First, we found that applying a minimum of 79.4 t ha−1 biochar was necessary to improve soil water and PO₄³⁻ retention; application rates below 79.4 t ha−1 exacerbated PO₄³⁻ leaching whereas treatments above 79.4 t ha−1 improved AWC by up to 34% compared to the control treatment. While biochar application rate did not affect soil nitric oxide or ammonia emissions, we did find that low biochar application rates increased soil nitrous oxide emission while higher application rates reduced emission compared to soil with no biochar. Overall, we found that lower and higher rates of biochar application can have contrasting effects on soil water and nutrient retention in an alkaline, desert cropland soil. Therefore, farmers and other land managers must consider potential drawbacks of lower application rates and threshold responses of higher application rates prior to large-scale biochar use in arid agroecosystems.

Effect of biochar application rate on macronutrient retention and leaching in two coconut growing soils

Low nutrient reserves and poor soil fertility management in coconut cultivation have limited coconut productivity. Biochar is one of the best solutions to improve soil nutrient reserves and fertility over time. This study explored the best rate of biochar application in coconut-growing soils to reduce leaching losses and macronutrient enrichment. Two major coconut-growing soil series; Madampe (Sandy) and Andigama (Sandy loam) were used in the experiment. <italic>Gliricidia</italic> wood biochar (BC) pyrolyzed at 700 °C was used to amend the 0-15 cm topsoil in PVC columns at the rates of 0% BC, 1% BC, 2% BC and 3% BC (w/w) with recommended doses of inorganic fertilizer. Columns were arranged in Completely Random Design (CRD) with three replicates and leached two weeks intervals over five months. Our findings revealed two distinct scenarios for sandy and sandy loam soils. Considering the retention of macronutrients in sandy loam soil treated with 2% and 3% biochar, the order of retention was P &gt; K &gt; Mg &gt; Ca. However, soil N was not altered substantially (<italic>P</italic> &gt; 0.05) with the amount of biochar amendment. Similarly, in sandy soil, 3% BC treatment demonstrated the sequence P &gt; Mg &gt; N = Ca, although soil K was not differed significantly (<italic>P</italic> &gt; 0.05) with biochar amendment rate. Albeit a once-in-lifetime application of 3% biochar could be recommended on coconut-growing sandy soils, application of this rate would be unprofitable. Thus, the 2% rate will be more appropriate for both sandy and sandy loam soils. These application rates must be validated through long-term field experiments under major coconut-growing soils.

Effect of biochar application rate on changes in soil labile organic carbon fractions and the association between bacterial community assembly and carbon metabolism with time

Biochar aging affects the stability of soil carbon. Analyzing the effect of biochar on soil organic carbon (SOC) forms and their relations with microbial community assembly and carbon metabolism with time is helpful for soil carbon sequestration (by adapting the farm management approach). Four treatments with no, low, medium, and high biochar application rates (0 %, 1 %, 2 %, and 4 % of the total dry weight of topsoil before winter wheat planting, abbreviated as control, LB, MB, and HB, respectively) were conducted in the field. The SOC and particulate organic carbon positively correlated with the biochar application rate. Biochar decreased readily oxidizable carbon (P < 0.05) after 8 months of application compared to the control; however, the difference disappeared with time. Biochar increased dissolved organic carbon (DOC) but had no effect on water- soluble organic carbon (WSOC); DOC and WSOC decreased with time. Furthermore, LB and HB stabilized the bacterial alpha diversities with time. Based on high-throughput sequencing, HB reduced the relative abundance of Actinobacteriota but increased that of Acidobacteria (P < 0.05) after 12 months of biochar application. Time-wise, the bacterial community assembly was determined by deterministic processes that were significantly affected by the available nitrogen, DOC, or WSOC. Compared with the control, biochar decreased bacterial links and improved bacterial metabolism of phenolic acids and polymers with time, as evidenced by Biolog EcoPlates. Structural equation modeling revealed that the contribution of bacterial assembly processes to carbon metabolism changed with time. Microbial carbon metabolism was most positively influenced by differences in the composition of bacterial specialists. These findings reinforced that changes in soil labile organic carbon were time-dependent but not necessarilty affected by the biochar application rate.

Targeted biochar application alters physical, chemical, hydrological and thermal properties of salt-affected soils under cotton-sugarbeet intercropping

Biochar application in agricultural salt-affected soils has shown strong potential to amend soil and promote production. The effect of biochar on soil properties and crop yield varies with crop, soil, biochar properties and climate. Thus, it is critical to select suitable biochar and their application amounts for ameliorating salt-affected soils while improving its conditions and crop yields. The objectives of this study were to investigate the effect of biochar application rates on soil properties, water and temperature conditions and crop yields in saline-alkali soils under cotton-sugarbeet intercropping. We used a three-year (2018–2020) field experiment with biochar application rates of 0, 10, 50 and 100 t ha−1 in 2018, 0, 10, 25, 50 and100 t ha−1 in 2019 and 0, 10, 25 and 30 t ha−1 in 2020. Soil bulk density decreased and thus porosity increased with application of biochar. Soil pH decreased with increasing biochar application amount and the rate of change ranged from −0.003 to −0.004 per ton of biochar. Biochar application at 10 t ha−1 increased soil water content (SWC) and weighted planar soil water storage (WPSWS) in all three experimental years, while oversupply of biochar decreased SWC. Application of biochar moderated soil temperature fluctuations. The yield of cotton and sugarbeet first increased and then decreased with increasing amount of biochar. Considering the effects of biochar on soil water, temperature, and crop yields, 10 t ha−1 biochar amount was proposed as an appropriate application rate for saline-alkali soils. The results provided valuable information on appropriate biochar rates to amend salt-affected soils and their properties while increase crop yields.

Effect of Biochar Application Rate on Physical and Hydro-physical Properties of A Dystric Cambisol

The field trial evaluating the effect of biochar on physical and hydro-physical properties of a Dystric Cambisol was carried out at the Research Grassland Station VatĂ­n. The observed variants of the biochar experiment were as follows: 1) the control without biochar, 2) the biochar rate of 15 t/ha applied to the topsoil, 3) the biochar rate of 30 t/ha applied to the topsoil and 4) the biochar rate of 45 t/ha applied to the topsoil. It was found out that even the highest rate of biochar 45 t/ha did not affect saturated hydraulic conductivity of the topsoil at the depth of 0.05-0.20 m. When monitoring bulk density, it was confirmed that the biochar rate of 45 t/ha significantly reduced bulk density from 1218 kg/m3 to 1169 kg/m3. In the crop rotation without manure and clover growing the application of biochar at the rate of 45 t/ha resulted in the relevant decline in the average value of bulk density from 1197 kg/m3 to 1138 kg/m3. In the Norfolk crop rotation there were the inconclusive differences in bulk density. The rate of 45 t/ha had a highly noticeable impact on porosity. It increased from 53.75% (0 t/ha) to 55.60%. The biochar doses did not affect the value of field capacity. The application of biochar at the rate of 45 t/ha caused the significant increase in the average value of aeration from 31.90% to 34.45%.

生物炭对褐土旱地玉米季氮转化功能基因、丛枝菌根真菌及N2O释放的影响

以豫西旱地玉米农田为研究对象，设置不同生物炭施用量处理（T0：不施用生物炭；T1：施用生物炭20 t/hm²；T2：施用生物炭40 t/hm²），采用密闭式静态箱法测定N₂O排放通量和荧光定量PCR法分析丛枝菌根（arbuscular mycorrhizal，AM）真菌、氨单加氧酶（amoA）、亚硝酸盐还原酶（nirS、nirK）以及氧化亚氮还原酶（nosZ）的基因丰度，同时测定土壤理化性状的变化。研究结果表明，随着生物炭施用量的增加，土壤pH和含水量呈增加趋势，土壤有机碳、全氮和铵态氮含量显著提高，土壤容重和硝态氮含量显著降低。T1和T2处理土壤有机碳含量分别较T0显著提高38.44%和71.01%；T1和T2处理土壤铵态氮含量分别较T0显著增加15.89%和30.46%；T2处理土壤全氮含量较T0处理显著提高14.87%；T1和T2处理土壤硝态氮含量分别较T0减少10.57%和21.40%。随着生物炭施用量的增加，AM真菌侵染率显著增加，T1和T2处理分别较T0处理提高71.88%和115.88%；AOA、AOB、nirK和nirS基因丰度显著降低；nosZ基因丰度增加。施加生物炭处理的N₂O排放通量和累积排放量均低于不施生物炭处理，具体表现为：T0 > T1 > T2。相关分析表明，生物炭施用量与AM真菌基因丰度呈显著正相关；与nosZ基因丰度呈正相关；与AOA、AOB、nirK、nirS基因丰度呈极显著负相关。N₂O排放通量与AOA、nirK、nirS基因丰度呈极显著正相关；与土壤含水量和土壤硝态氮含量呈显著正相关；与AM真菌、nosZ基因丰度、易提取球囊霉素含量、铵态氮含量呈极显著负相关。集成推进树（ABT）分析表明，AOA对N₂O排放的影响最大，其次是AM真菌和nirS。总之，生物炭处理改善土壤理化性质、提高土壤AM真菌侵染率、调节硝化、反硝化相关功能基因的丰度，减少N₂O气体排放，为旱地农田合理施用生物炭减少N₂O气体排放提供理论依据。;Biochar soil amendments are attracting the increased attention as one strategy to improve soil microbially ecological environment and regulate soil nitrogen cycle. The rainfed maize cropland in the western Henan was established to study the effects of biochar application rates (T0:0 t/hm², T1:20 t/hm², and T2:40 t/hm²) on soil physicochemical properties and N₂O emission fluxes using the static chamber/gas chromatography method, and the function marker genes of arbuscular mycorrhizal (AM) fungi, ammonia monooxygenase gene (amoA), nirK, nirS and nosZ, which were responsible for nitrification and denitrification using real-time fluorescence quota PCR. The results showed that the soil pH and water content increased, soil organic carbon, total nitrogen and ammonium nitrogen content increased significantly, and soil bulk density and nitrate nitrogen content decreased significantly with increasing biochar applied. Compared with T0 treatment, soil organic carbon increased significantly by 38.44% and 71.01% under T1 and T2 treatments, respectively; soil ammonium nitrogen content increased significantly by 15.89% and 30.46% under T1 and T2 treatments, respectively; soil total nitrogen content increased significantly by 14.87% under T2 treatment; nitrate nitrogen content decreased by 10.57% and 21.40% under T1 and T2 treatments, respectively. Moreover, the AM fungi colonization rate and nosZ gene abundance increased significantly, and AOA, AOB, nirK and nirS gene abundance decreased significantly with increasing biochar applied. Compared with T0 treatment, AM fungi increased significantly by 71.88% and 115.88% under T1 and T2 treatments, respectively. The N₂O emission fluxes and emission accumulations under biochar addition were all lower than those under no biochar, ranked as T0 > T1 > T2. The correlation analysis showed that the abundance of AM fungi was significantly positively (P<0.05) correlated with the biochar rate, and the abundance of nosZ gene and biochar rate was significant. There was a significantly negative correlation between AOA, AOB, nirK, nirS gene abundance and biochar rate (P<0.01). The N₂O emission fluxes showed a significantly positive correlation (P<0.01) with AOA, nirK, nirS, soil water content and nitrate nitrogen, but significantly negatively (P<0.01) correlated with AM fungi, nosZ, ammonium nitrogen and extractable glomalin related soil protein content. Aggregated boosted trees (ABT) analysis showed that the relative influence of AOA on N₂O emission fluxes was the largest, followed by AM fungi and nirK. In summary, the application of biochar improved soil physicochemical properties, increased soil AM fungi colonization rates, regulated nitrification and denitrification functional genes, and reduced N₂O emission, which provided a theoretical basis for the rational application of biochar and reduction of N₂O emissions in rainfed maize cropland.

An investigation of the effect of biochar application rates on CO2 emissions in soils under upland rice production in southern Guinea Savannah of Nigeria

Biochar is a chemically recalcitrant carbon-rich solid material used in soil for its potential to improve soil quality and sequester carbon. While the rate of application has implications for soil carbon dioxide (CO2) emission and the overall benefits of biochar, its effects are yet to be fully understood. To evaluate the effect of application rates of rice husk biochar on CO2 emissions, 91-day field experiments were conducted on three soil types (Anthraquic Ustorthent, Grossarenic Kandiustalf, and Ustic Quartzipsamment) in the southern Guinea Savannah of Nigeria, using three biochar application rates of 5, 15 and 25 t h−1, and control.A two-way ANOVA showed that cumulative CO2 emissions were significantly (p < 0.01) different between soil types and treatments, and soil type/treatment interactions were also significant at p = 0.05. The highest cumulative CO2–C emission of 2.77g/m2 was recorded in the Grossarenic Kandiustalf, while the least value of 2.11g/m2 was recorded in the Ustic Quartzipsamment. CO2 emission increased with increasing biochar application rates, with the highest (3.06 CO2–C g/m2) value recorded at 25 t/ha compared to 2.78 g/m2 and 1.52 g/m2 values recorded for 5 t/ha and control treatments respectively. While CO2 emissions increased with biochar application rate however, the percentage of biochar-C mineralized was higher at lower biochar rates, and differences were significant at p = 0.01. While 0.63 % of biochar C was mineralized under 5 t/ha biochar treatment, 0.15 % was recorded for 25 t/ha treatment. Factors that had significant correlation with CO2–C emission in the soils were biochar addition rate, soil pH, N, P, Ca, Mg and K. At day 91, there were no significant differences in CO2 emissions between amended treatments and control, and only a small percentage (<1) of biochar C had been mineralized.

Ameliorating Effect of Biochar on some Physical Properties of Sandy Soil and Water use Efficiency of Tomato (Solanum lycopersicum L.) Plant Grown under Drip Irrigation

Field experiments were conducted in two successive seasons (2018 and 2019) to investigate the effect of biochar application rates on weight basis (0.0 % (BC0), 0.2 % (BC1), 0.4 % (BC2) and 0.6 % (BC3)) on soil some physical properties, yield productivity and water use efficiency of tomato grown in sandy soil under drip irrigation. The results indicated that the soil physical properties, yield component and water use efficiency of tomato were significantly and positively affected (P ˂ 0.05) by biochar application treatments. Marked lowering in bulk density, saturated hydraulic conductivity, infiltration rate and cumulative infiltration depth of the sandy soil in both the two growing seasons as results of increasing application rate of biochar. In addition , increasing rate of biochar application resulted in significant increase of total porosity, mean weight diameter (MWD) , soil moisture constants (i.e., saturation percentage (SP), field capacity (F.C.), and wilting point (W.P.)), and soil water retention of sandy soil in both the two growing seasons. The measured available water content (AWC, %) showed a significant increase with increasing rate of biochar application which can be arranged in the order: BC3˃BC2˃BC1˃BC0. The results showed that the highest yield of tomato (32.4 and 31.9 ton.fed-1) was obtained due to BC2 treatment in both seasons. The maximum values of WUE (10.7 and 10.5 kg / m3) were associated with BC2 treatment (0.4 wt. % biochar) in both seasons. Consequently, under sandy soil conditions, application of biochar might be a promising amendment for ameliorating soil physical properties and subsequently enhancing tomato plant productivity. Tomato, Sandy soil, Biochar, Soil Physical Properties, Water use efficiency

Effect of Wheat-Straw Biochar on Nitrate Removal in Laboratory Denitrifying Bioreactors

Denitrifying bioreactors are an innovative nitrate-reduction strategy that reduces NO3-N with carbon substrate. In this study, application of biochar as a carbon substrate in DNBRs and the effect of biochar application rate and bioreactor heights on nitrate and ammonium concentration in the laboratory were investigated. Four mixtures of soil–biochar–wheat straw content of B0 = 0 (control treatment), B1 = 10, B2 = 20, and B3 = 30 percent of biochar were used. Also, to evaluate the effect of bioreactors heights, four heights 30, 60, 90, and 120 cm were used. The results showed that the nitrate concentration removal for control, B1, B2, and B3 treatment was 74.5, 81, 86.4, and 90.6% and biochar application rate, and bioreactor height have a significant effect on NO3-N removal and ammonium concentration. The results also showed that NO3-N removal and ammonium concentration increased with time. The effluent pH value of bioreactors does not have any particular trend during the experiment.

Biochar decreases soil N2O emissions in Moso bamboo plantations through decreasing labile N concentrations, N-cycling enzyme activities and nitrification/denitrification rates

Biochar application has been shown to be effective in mitigating soil N2O emission in agricultural soils. However, the effect of biochar on soil N2O emission in subtropical plantations and the underlining mechanisms are poorly understood. The objective of this study was to investigate the effect of biochar application rates (0, 5 and 15 t ha−1) on soil properties and N2O emissions within a Moso bamboo (Phyllostachys edulis) plantation in a 24-month field trial. Biochar application significantly (P < 0.05) decreased soil N2O emission, with the reduction rate positively related to the biochar application rate. The reduction in N2O emission by biochar application diminished over time. Biochar did not affect soil temperature (at 5 cm depth), and there were no significant relationships between N2O emission and either soil moisture content or soil microbial biomass C. However, biochar application significantly (P < 0.05) increased the water soluble organic C but decreased soil NH4+-N, NO3−-N and water soluble organic N (WSON) concentrations, soil urease and protease activities, and soil gross nitrification and denitrification rates. Soil N2O flux was positively (P < 0.05) correlated with soil NH4+-N, NO3−-N and WSON concentrations, soil urease and protease activities, and soil gross nitrification and denitrification rates, regardless of the treatment. Structural equation modeling suggests that biochar application decreased soil N2O emissions directly by decreasing soil gross nitrification and denitrification rates, and indirectly by decreasing concentrations of NH4+-N, NO3−-N and WSON, and the activities of urease and protease. We conclude that biochar application decreased soil N2O emission in the Moso bamboo plantation by decreasing labile N concentrations, N-cycling enzyme activities and nitrification/denitrification rates. Our findings suggest that biochar application can be an effective method to mitigate soil N2O emission in subtropical plantations.

Impacts of biochar application rates and particle sizes on runoff and soil loss in small cultivated loess plots under simulated rainfall

Increasing literature suggests that biochar can be used to improve soil fertility and subsequently benefit crop yield. However, the effects of biochar application rates and particle sizes on soil erosion processes have yet to be fully identified. The objective of the present study was to evaluate the influence of biochar with different application rates and particle sizes on soil erosion. Addition of biochar to loess generally increased the mean time to runoff by 19.47% relative to the control. The time to runoff decreased with an increase in the biochar application rates and fluctuated with a decrease in biochar particle sizes. The combined 1% and <0.25 mm biochar treatment yielded the longest time to runoff (2.97 min) and the lowest runoff (36.23 kg m−2 h−1) and soil loss (1.33 kg m−2 min−1). Biochar addition decreased the total runoff volume by 12.21% and generally inhibited soil loss under lower application rates (1% and 3%) while promoting soil loss under higher application rates (5% and 7%). With a decrease in biochar particle size, total runoff volume increased under the 5% and 7% biochar, but no uniform trend was observed under the 1% and 3% biochar treatments. The total soil loss increased with increasing biochar application rates, whereas a negative trend was observed with decreasing biochar particle sizes. The contribution of biochar application rates to runoff and soil loss rates was distinctly greater than the biochar particle sizes. Additionally, biochar addition could increase >2 mm water-stable soil aggregates and saturated hydraulic conductivity (Ksat) in this study. We inferred that the positive effects on soil and water loss were potentially due to the improvement in >2 mm water-stable soil aggregates and Ksat. The results implied that soil-biochar additions could be a potential measure for conserving soil and water in the Loess Plateau.

Effects of Biochar on Nitrous Oxide Fluxes and the Abundance of Related Functional Genes from Agriculture Soil in the North China Plain

To explore the effect and mechanism of biochar application in reducing nitrous oxide (N2O) content in agricultural soil, from March 27 to June 5 2015, pot experiments were conducted to study the effects of biochar application rates (CK, C1:5%, C2:10%, C3:15%, and C4:30%) (mass fraction) on soil N2O fluxes and the functional marker genes ammonia monooxygenase (amoA), nirK, nirS, and nosZ, which are responsible for nitrification and denitrification. The results revealed the following. ①The application of low doses of biochar (5%) promoted N2O emission. The application of middle and high doses of biochar reduced N2O emission. Furthermore, the application of biochar (15%) was found to be the best practice to reduce N2O emission. ② At the beginning of the experiment, biochar had a significant effect on the abundance of soil amoA and denitrification bacteria gene. Furthermore, the abundance of AOA and nirS had a significant positive correlation with the biochar rate, and the abundance of nirK gene and biochar rate were significant. There was a significant negative correlation between AOB and nosZ gene abundance and biochar rate. At the end of the experiment, AOA abundance correlated negatively with biochar rate, while there was a significantly positive relationship between AOB abundance and biochar rate. ③ At the beginning of the experiment, the N2O fluxes exhibited a significant negative correlation with AOA and nirS gene, indicating that N2O production was controlled by the abundance of AOA and nirS gene under high soil moisture content. At the end of the experiment, there was a significant positive correlation between N2O flux and nosZ gene, indicating that the production of N2O was regulated by the abundance of nosZ gene under low soil water content. The results of this study showed that the application of biochar altered the abundance of amoA and denitrification bacteria genes, and reduced N2O emission. These results provide a theoretical basis for a rational application of biochar in farmland.

Effects of Biochar Application Rates on Greenhouse Gas Emissions in the Purple Paddy Soil

In order to explore the effects of different amounts of biochar applied in purple paddy soil on greenhouse gas (GHG) emissions, potted experiments using a static opaque chamber and gas chromatography method were used to study the regulations and influences of biochar on soil greenhouse gas emission using five treatments:no fertilizer (CK), conventional fertilization (NPK), 10 t ·hm-2 biochar+NPK (LBC), 20 t ·hm-2 biochar+NPK (MBC), and 40 t ·hm-2 biochar+NPK (HBC). ① Soil CH4 emission flux reduced significantly with all biochar application treatments; the emission flux followed the order, from large to small, of NPK > CK > LBC > MBC > HBC. The CH4 emission flux of each treatment showed a single peak curve, and the peak value was mainly concentrated in the late growth stage of the paddy cropland. During the entire observation period, the emission flux of CH4 was between -0.05 mg ·(m2 ·h)-1 and 47.34 mg ·(m2 ·h)-1. The CO2 emission flux of each treatment was complicated and ranged from 32.95 mg ·(m2 ·h)-1 to 1350.88 mg ·(m2 ·h)-1. The CO2 emission flux of the LBC and MBC treatments showed bimodal curves, and the CO2 emission flux of other treatments showed single peak curves. In addition, all biochar treatments delayed the peak time of the CO2 emission flux. The N2O emission flux of each treatment ranged from -309.39 to 895.48 μg ·(m2 ·h)-1, and the N2O emission flux of the LBC treatment showed a bimodal curve, while other treatments showed single peak curves. ② Compared with the CK treatment, biochar treatment can significantly reduce the cumulative emissions of CH4 and promote the cumulative emissions of CO2 and N2O. The average amount of CH4 cumulative emissions followed the order CK > LBC > MBC > HBC, while the average amount of CO2 cumulative emissions followed LBC > MBC > HBC > CK, and the average amount of N2O cumulative emissions followed HBC > MBC≈LBC > CK. Compared with conventional fertilization treatment, different application rates of biochar addition significantly reduced CH4 and CO2 emissions. As more biochar was added, CH4 and CO2 cumulative emissions were lower. Although the regulation of N2O cumulative emissions on biochar addition was not obvious, the application of nitrogen fertilizer could promote the emission flux of N2O to some extent. ③ Over the time scale of 100 years, the integrated global warming potentials (GWP) of CH4 and N2O emission under different biochar treatment were decreased significantly, indicating that biochar combined with chemical fertilizer is an effective GHG emission reduction measure.

Impact of Biochar Addition on Productivity and Tubers Quality of Some Potato Cultivars Under Sandy Soil Conditions

THE PRESENT study was carried out during the two summer seasons of 2016 and 2017 to study the effect of biochar application rates (0, 1.25, 2.5 and 5 m3/feddan (fed.) = 4200 m2) on productivity and tubers quality of three potato cultivars i.e., Accent, Cara and Spunta grown under sandy soil conditions. Cara and Spunta cultivars recorded the highest values of morphological traits, leaf content of Ca, Mn and Cu, as well as tuber yield and quality. Cara cultivar recorded the maximum dry weight of different plant parts, while Spunta cv. recorded the highest values of photosynthetic pigments concentrations in the leaf tissues and the highest tuber starch content. Accent cv. recoded the lowest values of the last mentioned parameters and the lowest tuber nitrate content. Plant growth, leaf photosynthetic pigments and minerals content (N, P, K, Ca, Fe, Zn, Mn, and Cu), yield and its components, as well as tuber quality were significantly increased with increasing biochar application rates up to 5 m3/fed. Treated the three tested potato cultivars plants with different application rates of biochar increased plant growth, leaf photosynthetic pigments, minerals content and tuber yield and its components, compared to those untreated with biochar. Adding biochar at rates of 2.5 or 5 m3/fed. to the three tested potato cultivars Considerably gave the lowest values of leaf nitrate content. Treating Cara cultivars with biochar at rate of 5 m3/fed. gave the highest values of gross and net return, as well as benefits ratio, followed by adding 5 m3/fed. to Spunta plants. Finally, adding biochar to potato plants grown in sandy soil conditions obviously improves potato plant growth, plant chemical compositions, tuber yield and its components, with good tubers quality and increasing net return of potato production and keeps the environment less polluted.

Effects of biochar application on Suaeda salsa growth and saline soil properties

Pot experiments were conducted to study the effects of biochar application rates (5, 10, 20 g/kg) and types of wheat straw biochar (WS), corn stalk biochar (CS) and peanut shell biochar (PS) on Suaeda salsa (S. salsa) growth and properties of saline soil in Yellow River Delta. It was found that S. salsa yield increased from 11.7 to 115 % under WS application at a range of 5–10 g/kg compared with control. As biochar rate increased to 20 g/kg, the increment decreased to 102 %. The underground biomass of S. salsa only increased at 20 g/kg rate. The S. salsa growth respond to biochar followed the order of PS > WS > CS. Biochar application generally reduced saline soil pH and the effect was more obvious for WS. The content of total organic matter increased significantly at biochar rate of 10–20 g/kg. WS at higher application rate (20 g/kg) significantly increased available phosphorus content. At the same time, CS increased more available phosphorus content while PS decreased more of exchange sodium percentage. In generally, biochar application improved saline soil quality and enhanced plant growth although these effects should be tested in long-term period.

Effect of aging process on adsorption of diethyl phthalate in soils amended with bamboo biochar

Biochar is a carbonaceous sorbent and can be used as a potential material to reduce the bioavailability of organic pollutants in contaminated soils. In the present study, the adsorption and desorption of diethyl phthalate (DEP) onto soils amended with bamboo biochar was investigated with a special focus on the effect of biochar application rates and aging conditions on the adsorption capacity of the soils. Biochar amendment significantly enhanced the soil adsorption of DEP that increased with increasing application rates of biochar. However, the adsorption capacity decreased by two aging processes (alternating wet and dry, and constantly moist). In the soil with low organic carbon (OC) content, the addition of 0.5% biochar (without aging) increased the adsorption by nearly 98 times compared to the control, and exhibited the highest adsorption capacity among all the treatments. In the soil with high OC content, the adsorption capacity in the treatment of 0.5% biochar without aging was 3.5 and 3 times greater than those of the treatments of biochar aged by alternating wet and dry, and constantly moist, respectively. Moreover, constantly moist resulted in a greater adsorption capacity than alternating wet and dry treatments regardless of biochar addition. This study revealed that biochar application enhanced soil sorption of DEP, however, the enhancement of the adsorption capacity was dependent on the soil organic carbon levels, and aging processes of biochar.

Biochar application reduces nodulation but increases nitrogenase activity in clover

Biochar is produced from the pyrolysis of organic materials, and when buried in soil can act as a long term soil carbon (C) store. Evidence suggests that biochar can also increase crop yields, reduce nutrient leaching and increase biological nitrogen fixation in leguminous plants. However, the potential for increasing biological N2 fixation in agroecosystems is poorly understood, with inconsistent reports of root nodulation following biochar application. Therefore, the aim of this study was to determine the effect of biochar application rate and time since application on nodulation and nitrogenase activity in nodules of clover grown in a temperate agricultural soil. We used replicated field plots with three biochar application rates (0, 25 and 50 t ha−1). Three years after biochar amendment, the plots were further split and fresh biochar added at two different rates (25 and 50 t ha−1) resulting in double-loaded reapplications of 25 + 25 and 50 + 50 t ha−1. Three years after biochar application, there was no significant difference in the total number of root nodules between biochar-amended and unamended soil, regardless of the application rate. However, despite clover root nodules being of a similar number and size the level of nitrogenase activity of individual nodules in biochar-amended soil was significantly higher than in unamended soil. Reapplication of biochar resulted in decreased nodulation, although the rate of nitrogenase activity per nodule remained unaffected. In the short term, biochar influences root nodule number and localised N2 fixation per nodule; however, total nitrogenase activity for the whole root system remained unaffected by the application rate of biochar or time since its application. These results emphasise the importance of long-term field studies, with a variety of applications rates for determining the influence of biochar applications on N2-fixing organisms and in providing data that can meaningfully inform agronomic management decisions and climate change mitigation strategies.