Successive straw biochar application as a strategy to sequester carbon and improve fertility: A pot experiment with two rice/wheat rotations in paddy soil

Aims

A pot study spanning four consecutive crop seasons was conducted to compare the effects of successive rice straw biochar/rice straw amendments on C sequestration and soil fertility in rice/wheat rotated paddy soil.

Methods

We adopted 4.5 t ha^?1, 9.0 t ha^?1 biochar and 3.75 t ha^?1 straw for each crop season with an identical dose of NPK fertilizers.

Results

We found no major losses of biochar-C over the 2-year experimental period. Obvious reductions in CH₄ emission were observed from rice seasons under the biochar application, despite the fact that the biochar brought more C into the soil than the straw. N₂O emissions with biochar were similar to the controls without additives over the 2-year experimental period. Biochar application had positive effects on crop growth, along with positive effects on nutrient (N, P, K, Ca and Mg) uptake by crop plants and the availability of soil P, K, Ca and Mg. High levels of biochar application over the course of the crop rotation suppressed NH₃ volatilization in the rice season, but stimulated it in the wheat season.

Conclusions

Converting straw to biochar followed by successive application to soil is viable for soil C sequestration, CH₄ mitigation, improvements of soil and crop productivity. Biochar soil amendment influences NH₃ volatilization differently in the flooded rice and upland wheat seasons, respectively.     

Effect of Compost and Biochar on Heavy Metals Phytostabilization by the Halophytic Plant Old Man Saltbush [Atriplex Nummularia Lindl]

Remediation of soils is vital to mitigate the negative effects of heavy metals in ecosystems. There is little information available about the metals’ phytostabilization potential of old man saltbush plants [Atriplex nummularia]. A pot experiment in a randomized complete block design was conducted to study the accumulation of heavy metals by old man saltbush plants, as affected by the application of compost and biochar. The cultivation of A. nummularia is an effective tool in immobilizing metals in the contaminated soils. The cultivation of metal-contaminated soil with A. nummularia reduced the availability of Zn, Cu, Cd, and Pb by 20%, 4%, 21%, and 28%, respectively, in comparison to the non-cultivated soil. Zn, Cu, Cd, and Pb concentrations in the aboveground parts of old man saltbush plants were 70–100, 50–80, 4–5, and 50–90 mg/kg of dry biomass. The higher Zn, Cu, Cd, and Pb concentrations were accumulated in the roots, and the lower concentrations were transferred to the shoots of old man saltbush plants. Compost reduced the concentration of Zn, Cu, Cd, and Pb in the shoots by 10%, 19%, 20%, and 6%, respectively, compared to the control soil. Biochar reduced the concentrations of Zn, Cu, and Pb in the shoots by 30%, 38%, and 44%, respectively, compared to the control. Compost had a lower effect in reducing the metals uptake as biochar. Biochar reduced the uptake of Zn, Cu, and Pb in the shoots of the tested plant by 22%, 23%, and 41%, respectively, in comparison to compost. Based on the obtained results, old man saltbush has good characteristics to be a promising candidate for phytostabilization strategies of metal-contaminated soils. Moreover, biochar is a good tool to enhance metals’ phytostablization.     

Biochar stimulates the decomposition of simple organic matter and suppresses the decomposition of complex organic matter in a sandy loam soil

Incorporating crop residues and biochar has received increasing attention as tools to mitigate atmospheric carbon dioxide (CO₂) emissions and promote soil carbon (C) sequestration. However, direct comparisons between biochar, torrefied biomass, and straw on both labile and recalcitrant soil organic matter (SOM) remain poorly understood. In this study, we explored the impact of biochars produced at different temperatures and torrefied biomass on the simple C substrates (glucose, amino acids), plant residues (Lolium perenne L.), and native SOM breakdown in soil using a ¹⁴C labeling approach. Torrefied biomass and biochars produced from wheat straw at four contrasting pyrolysis temperatures (250, 350, 450, and 550 °C) were incorporated into a sandy loam soil and their impact on C turnover compared to an unamended soil or one amended with unprocessed straw. Biochar, torrefied biomass, and straw application induced a shift in the soil microbial community size, activity, and structure with the greatest effects in the straw‐amended soil. In addition, they also resulted in changes in microbial carbon use efficiency (CUE) leading to more substrate C being partitioned into catabolic processes. While overall the biochar, torrefied biomass, and straw addition increased soil respiration, it reduced the turnover rate of the simple C substrates, plant residues, and native SOM and had no appreciable effect on the turnover rate of the microbial biomass. The negative SOM priming was positively correlated with biochar production temperature. We therefore ascribe the increase in soil CO₂ efflux to biochar‐derived C rather than that originating from SOM. In conclusion, the SOM priming magnitude is strongly influenced by both the soil organic C quality and the biochar properties. In comparison with straw, biochar has the greatest potential to promote soil C storage. However, straw and torrefied biomass may have other cobenefits which may make them more suitable as a CO₂ abatement strategy.     

Impact of biochar application on nitrogen nutrition of rice, greenhouse-gas emissions and soil organic carbon dynamics in two paddy soils of China

Aims

Two field microcosm experiments and ¹⁵N labeling techniques were used to investigate the effects of biochar addition on rice N nutrition and GHG emissions in an Inceptisol and an Ultisol.

Methods

Biochar N bioavailability and effect of biochar on fertilizer nitrogen-use efficiency (NUE) were studied by ¹⁵N-enriched wheat biochar (7.8803 atom% ¹⁵N) and fertilizer urea (5.0026 atom% ¹⁵N) (Experiment I). Corn biochar and corn stalks were applied at 12 Mg?ha^?1 to study their effects on GHG emissions (Experiment II).

Results

Biochar had no significant impact on rice production and less than 2 % of the biochar N was available to plants in the first season. Biochar addition increased soil C and N contents and decreased urea NUE. Seasonal cumulative CH₄ emissions with biochar were similar to the controls, but significantly lower than the local practice of straw amendment. N₂O emissions with biochar were similar to the control in the acidic Ultisol, but significantly higher in the slightly alkaline Inceptisol. Carbon-balance calculations found no major losses of biochar-C.

Conclusion

Low bio-availability of biochar N did not make a significantly impact on rice production or N nutrition during the first year. Replacement of straw amendments with biochar could decrease CH₄ emissions and increase SOC stocks.     

Control of Late Blight (Phytophthora capsici ) in Pepper Plant with a Compost Containing Multitude of Chitinase-producing Bacteria

Compost sustaining a multitude of chitinase-producing bacteria was evaluated in a greenhouse study as a soil amendment for the control of late blight (Phytophthora capsici L.) in pepper (Capsicum annuum L.). Microbial population and exogenous enzyme activity were measured in the rhizosphere and correlated to the growth and health of pepper plant. Rice straw was composted with and without a chitin source, after having been inoculated with an aliquot of coastal area soil containing a known titer of chitinase-producing bacteria. P. capsici inoculated plants cultivated in chitin compost-amended soil exhibited significantly higher root and shoot weights and lower root mortality than plants grown in pathogen-inoculated control compost. Chitinase and β-1,3-glucanase activities in rhizosphere of plants grown in chitin compost-amended soil were twice that seen in soil amended with control compost. Colony forming units of chitinase-producing bacteria isolated from rhizosphere of plants grown in chitin compost-amended soil were 10³ times as prevalent as bacteria in control compost. These results indicate that increasing the population of chitinase-producing bacteria and soil enzyme activities in rhizosphere by compost amendment could alleviate pathogenic effects of P. capsici.     

Response of soil carbon dioxide fluxes,soil organic carbon and microbial biomass carbon to biochar amendment: a meta‐analysis

Biochar as a carbon‐rich coproduct of pyrolyzing biomass, its amendment has been advocated as a potential strategy to soil carbon (C) sequestration. Updated data derived from 50 papers with 395 paired observations were reviewed using meta‐analysis procedures to examine responses of soil carbon dioxide (CO₂) fluxes, soil organic C (SOC), and soil microbial biomass C (MBC) contents to biochar amendment. When averaged across all studies, biochar amendment had no significant effect on soil CO₂ fluxes, but it significantly enhanced SOC content by 40% and MBC content by 18%. A positive response of soil CO₂ fluxes to biochar amendment was found in rice paddies, laboratory incubation studies, soils without vegetation, and unfertilized soils. Biochar amendment significantly increased soil MBC content in field studies, N‐fertilized soils, and soils with vegetation. Enhancement of SOC content following biochar amendment was the greatest in rice paddies among different land‐use types. Responses of soil CO₂ fluxes and MBC to biochar amendment varied with soil texture and pH. The use of biochar in combination with synthetic N fertilizer and waste compost fertilizer led to the greatest increases in soil CO₂ fluxes and MBC content, respectively. Both soil CO₂ fluxes and MBC responses to biochar amendment decreased with biochar application rate, pyrolysis temperature, or C/N ratio of biochar, while each increased SOC content enhancement. Among different biochar feedstock sources, positive responses of soil CO₂ fluxes and MBC were the highest for manure and crop residue feedstock sources, respectively. Soil CO₂ flux responses to biochar amendment decreased with pH of biochar, while biochars with pH of 8.1–9.0 had the greatest enhancement of SOC and MBC contents. Therefore, soil properties, land‐use type, agricultural practice, and biochar characteristics should be taken into account to assess the practical potential of biochar for mitigating climate change.     

Carbon footprint of rice production under biochar amendment – a case study in a Chinese rice cropping system

As a controversial strategy to mitigate global warming, biochar application into soil highlights the need for life cycle assessment before large‐scale practice. This study focused on the effect of biochar on carbon footprint of rice production. A field experiment was performed with three treatments: no residue amendment (Control), 6 t ha^?1 yr^?1 corn straw (CS) amendment, and 2.4 t ha^?1 yr^?1 corn straw‐derived biochar amendment (CBC). Carbon footprint was calculated by considering carbon source processes (pyrolysis energy cost, fertilizer and pesticide input, farmwork, and soil greenhouse gas emissions) and carbon sink processes (soil carbon increment and energy offset from pyrolytic gas). On average over three consecutive rice‐growing cycles from year 2011 to 2013, the CS treatment had a much higher carbon intensity of rice (0.68 kg CO₂‐C equivalent (CO₂‐C_e) kg^?1 grain) than that of Control (0.24 kg CO₂‐C_e kg^?1 grain), resulting from large soil CH₄ emissions. Biochar amendment significantly increased soil carbon pool and showed no significant effect on soil total N₂O and CH₄ emissions relative to Control; however, due to a variation in net electric energy input of biochar production based on different pyrolysis settings, carbon intensity of rice under CBC treatment ranged from 0.04 to 0.44 kg CO₂‐C_e kg^?1 grain. The results indicated that biochar strategy had the potential to significantly reduce the carbon footprint of crop production, but the energy‐efficient pyrolysis technique does matter.     

秸秆生物质炭对土壤结构体与活性碳分布、转化酶动力学参数及小麦生长的影响

为探明生物质炭输入土壤后与水稳性团聚体的作用机理,及对土壤活性碳库、微生物活性、作物生长的促进作用。以生物质炭和秸秆碳为外源碳材料,两者等碳量添加条件下,在小麦不同生育期采用湿筛法、电镜扫描、酶动力学方程等方法,测定土壤结构、酶活性、活性有机碳、及小麦产量等指标的响应情况。结果表明:生物质炭添加下,土壤0.25 mm大颗粒团聚体显著增加了16.9%—45.8%;土壤结构体分布以土壤大颗粒团聚体为主,含量约为小颗粒团聚体的2倍。生物质炭少量或适量添加(0.8%或2.4%),土壤微生物量碳增加了9.7%—33.6%,溶解性有机碳降低了12.6%—27.5%;而过量添加下(8%),则呈现正好相反的规律。生物质炭输入下,转化酶动力学参数Km、Vmax、k分别下降了17.3%、17.0%、16.1%。生物质炭适量添加下,小麦产量增加了14.9%—19.1%;秸秆3%和10%添加水平下,小麦产量则下降了37.3%和90.1%。整体而言,生物质炭通过增加0.25 mm大颗粒团聚体的形成及土壤转化酶的活性来促进土壤结构和作物的生长的改善,且生物质炭在2.4%水平下的生物质炭添加改善作用最为突出,有助于研究区域过剩秸秆资源的资源化利用。     

Effects of Biochar Addition on CO2 and N2O Emissions following Fertilizer Application to a Cultivated Grassland Soil

Carbon (C) sequestration potential of biochar should be considered together with emission of greenhouse gases when applied to soils. In this study, we investigated CO₂ and N₂O emissions following the application of rice husk biochars to cultivated grassland soils and related gas emissions tos oil C and nitrogen (N) dynamics. Treatments included biochar addition (CHAR, NO CHAR) and amendment (COMPOST, UREA, NO FERT). The biochar application rate was 0.3% by weight. The temporal pattern of CO₂ emissions differed according to biochar addition and amendments. CO₂ emissions from the COMPOST soils were significantly higher than those from the UREA and NO FERT soils and less CO₂ emission was observed when biochar and compost were applied together during the summer. Overall N₂O emission was significantly influenced by the interaction between biochar and amendments. In UREA soil, biochar addition increased N₂O emission by 49% compared to the control, while in the COMPOST and NO FERT soils, biochar did not have an effect on N₂O emission. Two possible mechanisms were proposed to explain the higher N₂O emissions upon biochar addition to UREA soil than other soils. Labile C in the biochar may have stimulated microbial N mineralization in the C-limited soil used in our study, resulting in an increase in N₂O emission. Biochar may also have provided the soil with the ability to retain mineral N, leading to increased N₂O emission. The overall results imply that biochar addition can increase C sequestration when applied together with compost, and might stimulate N₂O emission when applied to soil amended with urea.     

不同磷水平配施生物炭对土壤磷有效性

生物炭在提高土壤磷素有效性及促进作物生长方面具有显著作用,但其效果因土壤类型不同存在较大差异。试验以赤红壤(pH 4.91)和褐土(pH 7.24)为供试土壤,设置3种磷肥水平(0、30、90 kg P·hm^-2,分别以不施磷、低磷、高磷表示)配施稻秆生物炭(0、4%)的大豆盆栽试验,研究了不同磷水平下配施生物炭对土壤磷有效性、磷酸单酯酶活性和植株磷吸收的影响。结果表明: 不同磷水平配施生物炭显著提高了两种土壤的速效磷和全磷含量,且低磷水平添加生物炭处理速效磷增幅最大,在赤红壤和褐土的增幅分别为192.6%和237.1%。与低磷相比,赤红壤中低磷配施生物炭处理的碱性磷酸单酯酶活性显著增加78.9%,活性有机磷含量降低39.3%,同时显著促进了植株生长与磷吸收;生物炭添加显著降低了褐土活性有机磷含量,但不同处理对土壤磷酸单酯酶活性和植株生长无显著影响。土壤活性有机磷含量与速效磷含量均呈显著负相关。综上,生物炭对土壤磷有效性的作用因土壤类型和磷肥水平差异而不同,其在赤红壤上对植株生长和磷吸收的促进效应强于褐土,且在低磷条件下效果更佳。本研究为生物炭在减施磷肥和促进大豆磷吸收,特别是在赤红壤上的应用提供了科学依据。     

施用生物炭和秸秆还田对华北农田CO2、N2O排放的影响

以华北农田冬小麦-夏玉米轮作体系连续6a施用生物炭和秸秆还田的土壤为研究对象,于2013年10月—2014年9月,采用静态暗箱-气相色谱法,对CO_2、N_2O通量进行了整个轮作周期的连续观测,探究施用生物炭与秸秆还田对其排放通量的影响。试验共设4个处理:CK(对照)、C1(低量生物炭4.5 t hm~(-2)a~(-1))、C2(高量生物炭9.0 t hm~(-2)a~(-1))和SR(秸秆还田straw return)。结果表明:在整个轮作周期内,各处理CO_2、N_2O通量随时间的变化趋势基本一致。随着生物炭施用量的增加,CO_2排放通量分别增加了0.3%—90.3%(C1)、1.0%—334.2%(C2)和0.4%—156.3%(SR)。其中,C2处理对CO_2累积排放量影响最大,增幅为42.9%。对N_2O而言,C2处理显著降低了N_2O累积排放量,但增加了CO_2和N_2O排放的综合增温潜势,C1和SR处理对N_2O累积排放量及综合增温潜势均没有显著影响。相关分析表明,土壤温度和土壤含水量是影响CO_2通量最主要的因素,两者之间呈极显著的正相关关系;N_2O通量与土壤温度、土壤含水量、NO_3~--N和NH_4~+-N均表现出极显著的正相关关系,而与土壤p H值表现出极显著的负相关关系。由此可见,添加生物炭对于减少氮素的气体损失具有较大的潜力。     

Molecular Response of the Bloom-Forming Cyanobacterium, Microcystis aeruginosa, to Phosphorus Limitation

Cyanobacteria blooms caused by species such as Microcystis have become commonplace in many freshwater ecosystems. Although phosphorus (P) typically limits the growth of freshwater phytoplankton populations, little is known regarding the molecular response of Microcystis to variation in P concentrations and sources. For this study, we examined genes involved in P acquisition in Microcystis including two high-affinity phosphate-binding proteins (pstS and sphX) and a putative alkaline phosphatase (phoX). Sequence analyses among ten clones of Microcystis aeruginosa and one clone of Microcystis wesenbergii indicates that these genes are present and conserved within the species, but perhaps not the genus, as phoX was not identified in M. wesenbergii. Experiments with clones of M. aeruginosa indicated that expression of these three genes was strongly upregulated (50- to 400-fold) under low inorganic P conditions and that the expression of phoX was correlated with alkaline phosphatase activity (p < 0.005). In contrast, cultures grown exclusively on high levels of organic phosphorus sources (adenosine 5′-monophosphate, β-glycerol phosphate, and d-glucose-6-phosphate) or under nitrogen-limited conditions displayed neither high levels of gene expression nor alkaline phosphatase activity. Since Microcystis dominates phytoplankton assemblages in summer when levels of inorganic P (P_i) are often low and/or dominate lakes with low P_i and high organic P, our findings suggest this cyanobacterium may rely on pstS, sphX, and phoX to efficiently transport P_i and exploit organic sources of P to form blooms.     

Contrasting effects of maize residue,coal gas residue and their biochars on nutrient mineralization,enzyme activities and CO2 emissions in sandy loess soil

Mismanagement of crop straw and coal gas residue threatens the atmosphere and the economy. Nevertheless, thermal-pyrolysis is an option for management that turns bio-waste into biochar; its viability and adoption by the public as soil amendments is dependent on the agronomic and environmental values compared between biochar and the raw materials. We undertook a 60-day short-term analysis to assess the impact of various wastes and biochars, as well as inorganic nutrients (N), on carbon dioxide (CO₂) fluxes, soil enzyme activities, soil fertility status, and microbial activities. There were eight treatments of soil amendments: without an amendment (CK), Nutrients (N), straw + nutrients (S+N), straw biochar + nutrients (SB+N), coal gas residue + nutrients (C+N), coal gas residue biochar + nutrients (CB+N), straw + straw biochar + nutrients (S+SB+N) and coal gas residue waste + coal gas residue biochar + nutrients (C+ CB +N). The results indicated that soil EC, pH, nitrate N (NO₃^–- N), SOC, TN and available K were significantly (p < 0.05) increased coal gas residue biochar and combined with coal fly ash as compared to maize straw biochar and combined with maize straw and N treatments. The higher concentrations of soil MBC and MBN activities were increased in the maize straw application, while higher soil enzyme activity such as, invertase, urease and catalase were enhanced in the coal fly ash derived biochar treatments. The higher cumulative CO₂ emissions were recorded in the combined applications of maize straw and its biochar as well as coal gas residue and its biochar treatment. Our study concludes, that maize straw and coal fly ash wastes were converted into biochar product could be a feasible substitute way of discarding, since land amendment and decreased CO₂ fluxes and positive changes in soil microbial, and chemical properties, and can be confirmed under long-term conditions for reduction of economical and environment issues.     

Comparative efficiency of wheat straw and sugarcane bagasse biochar reduces the cadmium bioavailability to spinach and enhances the microbial activity in contaminated soil

Abstract

Biochar is considered a novel soil amendment for cadmium (Cd) stabilization in contaminated soils. A pot experiment was conducted to examine the efficiency of wheat straw and sugarcane bagasse induced biochar on Cd mobility in soil and its bioavailability to spinach in contaminated soil. Soil pH, Cd contents in plant tissues and microbial biomass were examined. Results showed that Cd was significantly decreased by 30.95% and 20.83% with wheat straw and sugarcane bagasse biochar at 2% application rate respectively, relative to the control. Similarly, Cd contents were decreased in plants shoots by 15.41 and 14.33%, while in roots by 48.3 and 35.54%, when wheat straw and sugarcane biochar were added at 2% application rate respectively. Moreover, soil microbial biomass was significantly increased with the application of all biochar types and their applications rates. Finally, wheat straw biochar at 2% application rate can be considered as an effective approach for Cd stabilization in contaminated soils.     

Biochar co-compost improves nitrogen retention and reduces carbon emissions in a winter wheat cropping system

Organic amendments, such as compost and biochar, mitigate the environmental burdens associated with wasting organic resources and close nutrient loops by capturing, transforming, and resupplying nutrients to soils. While compost or biochar application to soil can enhance an agroecosystem's capacity to store carbon and produce food, there have been few field studies investigating the agroecological impacts of amending soil with biochar co-compost, produced through the composting of nitrogen-rich organic material, such as manure, with carbon-rich biochar. Here, we examine the impact of biochar co-compost on soil properties and processes by conducting a field study in which we compare the environmental and agronomic impacts associated with the amendment of either dairy manure co-composted with biochar, dairy manure compost, or biochar to soils in a winter wheat cropping system. Organic amendments were applied at equivalent C rates (8 Mg C ha⁻¹). We found that all three treatments significantly increased soil water holding capacity and total plant biomass relative to the no-amendment control. Soils amended with biochar or biochar co-compost resulted in significantly less greenhouse gas emissions than the compost or control soils. Biochar co-compost also resulted in a significant reduction in nutrient leaching relative to the application of biochar alone or compost alone. Our results suggest that biochar co-composting could optimize organic resource recycling for climate change mitigation and agricultural productivity while minimizing nutrient losses from agroecosystems.     

生物炭添加对不同水氮条件下芦苇生长和氮素吸收的影响

生物炭能改良土壤从而促进植物生长和氮素吸收,但其作用效果是否受水氮条件的影响尚不清楚。以湿地植物芦苇为研究对象,在3种氮添加水平（无添加,30 kg hm^-2 a^-1和60 kg hm^-2 a^-1）和两种水分（淹水和非淹水）条件下分别进行生物炭添加和不添加处理,结果表明：（1）生物炭添加能促进芦苇根系生长,在非淹水条件下根系生物量增加了40.5%,在淹水条件下根系生物量增加了20.1%。（2）生物炭添加能促进非淹水条件下芦苇的氮素吸收,能提高淹水条件下芦苇的氮素生产力。（3）生物炭添加加剧了土壤氮素损失,且在非淹水高氮条件下作用最强,可能是由于生物炭促进了芦苇的氮素吸收。芦苇氮素吸收速率与土壤氮损失之间存在显著的正相关关系。因此,在添加生物炭时,需要考虑土壤水分状况和氮素富集程度以及植物的氮素吸收偏好。该研究结果可为生物炭在湿地生态系统中的应用提供参考。     

施用生物炭基肥对喀斯特石灰土磷元素特性的影响

以贵州省喀斯特山地石灰土为研究对象,采用盆栽试验方法,研究施用生物炭(稻壳炭)、猪粪堆肥和NPK肥3种肥料制成的生物炭基肥,测定土壤中不同形态磷含量、碱性磷酸酶活性及刺槐幼苗生物量。试验共设10个处理,分别为CK、M、F、MF、RH1MF、RH2MF、RH4MF、RH8MF、RH4M、RH4F(其中CK代表对照,M代表堆肥,F代表化肥,RH代表稻壳炭,数字代表生物炭按炭土质量比计算在生物炭基肥中的配比)。结果表明,施用生物炭基肥可显著提高喀斯特石灰土中总磷、有效磷、有机磷、微生物量磷含量及刺槐幼苗生物量,生物炭高施用量下处理(RH8MF)的效果更好,且4种不同形态的磷含量相互之间呈极显著正相关(P0.01);生物炭中等用量配比下生物炭基肥处理(RH2MF、RH4MF)的土壤碱性磷酸酶活性最高,分别比CK提高82.7%、63.4%。综上所述,施用生物炭基肥,尤其在生物炭较高施用量下,可以显著改善喀斯特石灰土中磷素含量,可改善石灰土中磷素含量较低状况,提高喀斯特山地人工幼林地生态恢复的成效。     

Effectiveness of biochar and compost on improving soil hydro-physical properties,crop yield and monetary returns in inceptisol subtropics

Organic manures in combination with biochar might improve efficacy of biochar in improving soil functions related to hydro-physical properties and a field experiment was conducted over the course of two years with two levels of biochar @ 0 and 2tha⁻¹ and four levels of compost (100% recommended dose of N through farm yard manure, 100% recommended dose of N through vermicompost, 50% recommended dose of N through farm yard manure, and vermicompost each, and unfertilized control). Each treatment was replicated three times in factorial randomized block design (RBD). The objective of this research was to determine the effects of biochar and compost on soil hydro-physical properties, water use efficiency, monetary returns and yield of knolkhol (Brassica oleracea var. gongyloides L.) under sub-tropics of North West India. Compared with no-biochar, application of biochar significantly increased knolkhol yield by 7.8% and soil properties (infiltration rate, aggregate stability, maximum water holding capacity and hydraulic conductivity). Similarly, integration of compost significantly enhanced the soil water retention, aggregate stability, hydraulic conductivity and crop yield and gave highest infiltration rate, water retention, hydraulic conductivity and crop yield under M3 (50 % N through farm yard manure, +50 % N through vermicompost) treatment. Furthermore, synergetic positive effect of biochar and compost were noted for soil infiltration rate (4–38%), water retention (0.9–13.7%), aggregate stability (6–10.7%) and yield (6–11.9%) over the sole application of compost. Combined use of farm yard manure, and vermicompost accompanied by biochar resulted in highest net returns and B:C ratio. Biochar in combination with farm yard manure, and vermicompost can enhance soil hydraulic properties resulting in increased crop yield and maximum monetary returns under subtropical conditions.     

西南喀斯特区坡耕地秸秆覆盖对土壤生态化学计量特征及产量的影响

土壤养分亏缺是限制作物生长的关键因素,同时也是制约作物产量的重要影响因子。为提高西南喀斯特区坡耕地土壤肥力和作物产量,于2018—2019年连续两年在贵州省黔西县开展了野外原位径流小区观测试验。通过该试验探讨不同秸秆覆盖率下土壤碳(C)、氮(N)、磷(P)、钾(K)含量及其生态化学计量特征,揭示不同秸秆覆盖率下土壤养分状况及土壤改良效果。共设6个秸秆覆盖梯度,玉米单作+秸秆覆盖(SM₀—SM₅,0,1111、2222、3889、5556,6944 kg/hm~2),其中SM₀为对照组(CK)。结果表明：(1)秸秆覆盖不同程度增加了土壤有机碳(SOC)、全氮(TN)及全磷(TP)含量,总体上随覆盖量的增加而增加,尤其是覆盖量较多的情况下(SM₄,SM₅),均显著高于对照(P<0.05),但两者之间差异不显著(P> 0.05),而全钾(TK)则随着覆盖量的增加而减少。(2)在高秸秆覆盖条件下(SM₄,SM₅),除了N∶P外,两...     

秸秆还田对玉米根际氨氧化微生物群落及红壤硝化潜势的影响

为探讨酸性红壤根际氨氧化微生物群落以及硝化作用对不同秸秆还田处理的响应,基于中国科学院鹰潭红壤生态实验站设置的秸秆还田长期试验平台(9年),采用荧光定量PCR和高通量测序技术,研究不同秸秆还田处理(不施肥(CK);氮磷钾肥(NPK);氮磷钾肥+秸秆(NPKS);氮磷钾肥+秸秆猪粪配施(NPKSM);氮磷钾肥+秸秆生物炭(NPKB))下玉米根际土壤氨氧化古菌(ammonia-oxidizing archaea, AOA)和细菌(ammonia-oxidizing bacteria, AOB)丰度和群落结构的变化,揭示了秸秆还田对根际氨氧化微生物群落结构和硝化潜势(potential nitrification activity, PNA)的影响机制。结果发现：相比CK和NPK处理,秸秆还田显著提高了土壤养分含量和硝化潜势,其中有机碳(SOC)、全氮(TN)、全磷(TP)、速效磷(AP)、速效钾(AK)、硝态氮(NO~-₃-N)和铵态氮(NH~+₄-N)含量显著增加,NPKSM处理对土壤肥力提升效果最佳。AOA的硝化潜势显著高于AOB,表明AOA...