Effect of cow manure biochar on maize productivity under sandy soil condition

In this study, we performed a greenhouse experiment to investigate the effect of cow manure biochar on maize yield, nutrient uptake and physico‐chemical properties of a dryland sandy soil. Biochar was derived from dry cow manure pyrolysed at 500 °C. Cow manure biochar was mixed with a sandy soil at the rate equivalent to 0, 10, 15 and 20 t biochar per hectare. Maize was used as a test crop. Results of the study indicated that cow manure biochar contains some important plant nutrients which significantly affected the maize crop growth. Maize yield and nutrient uptake were significantly improved with increasing the biochar mixing rate. Application of biochar at 15 and 20 t/ha mixing rates significantly increased maize grain yield by 150 and 98% as compared with the control, respectively. Maize net water use efficiency (WUE) increased by 6, 139 and 91% as compared with the control, with the 10, 15 and 20 t/ha mixing rate, respectively. Nutrient uptake by maize grain was significantly increased with higher biochar applications. Application of cow manure biochar improved the field‐saturated hydraulic conductivity of the sandy soil, as a result net WUE also increased. Results of the soil analysis after the harvesting indicated significant increase in the pH, total C, total N, Oslen‐P, exchangeable cations and cation exchange capacity. The results of this study indicated that application of cow manure biochar to sandy soil is not only beneficial for crop growth but it also significantly improved the physico‐chemical properties of the coarse soil.     

Mineral composition of field grown winter wheat inoculated with phosphorus solubilizing bacteria at different plant growth stages

A two year field experiment was conducted in field conditions using wheat (Triticum aestivum ssp. vulgare L. cv. Bezostaja) as the test plant for the evaluation of phosphate solubilizing (+PS) microorganisms. Bacterial strains significantly (P < 0.05) increased plant biomass (by 13 to 36%) without plant P enrichment. Only Bacillus sp. #189 significantly (P < 0.05) raised plant P-content, biomass and rhizosphere soil Olsen P at Zadoks Scale 62 simultaneously. Inoculations variably increased plant potassium (K-), magnesium (Mg-), zinc (Zn-), and managenese (Mn-) contents at harvest (Zadoks 92) but not earlier (Zadoks 31 and 61). The enrichment of the inoculated plants with nutrients other than P indicates the presence of alternative plant growth promoting mechanisms. This study showed that promising phosphate solubilizing microorganisms could increase not only the P content of the plants, but also the soil available P in rhizosphere transiently.     

Effects of crop growth and soil treatments on microbial C,N, and P in dry tropical arable land

We studied the dynamics of microbial C, N, and P in soil cropped with rice (Oryza sativa) and lentils (Lens culinaris) in a dryland farming system. The crop biomass and grain yield were also studied. The microbial biomass and its N and P contents were larger under the lentil than under the rice crop. Microbial nutrients decreased as the crops grew and then increased again. Farmyard manure and NPK fertilizer applications increased the level of microbial nutrients, crop biomass, and grain yield by 35–80%, 55–85%, and 74–86%, respectively. However, these applications had no significant effect on most of the soil physicochemical properties in the short term. The microbial biomass was correlated with the crop biomass and grain yield. The calculated flux of N and P through the microbial biomass ranged from 30–45 and 10–19 kg ha^-1 year^-1, respectively. Cultivation of a cereal crop followed by a leguminous crop sustains higher levels of microbial nutrients and hence greater fertility in impoverished tropical arable soils. The soil microbial biomass appears to contribute significantly to crop productivity by releasing nutrients, and applications of manure, either alone or with fertilizers, promote this effect more strongly than the application of NPK fertilizers alone.     

Effect of organic manure on the biological activities associated with insoluble phosphorus release in a blue purple paddy soil

Abstract

This study examined the effects of organic manure and chemical fertilizer on soil microflora, soil respiration, number of inorganic phosphate solubilizing bacteria, and organic phosphorus (P) mineralizing bacteria. The inorganic phosphate solubilizing rate, organic P mineralizing rate, and selected enzyme activities in a blue purple paddy soil were also studied. The results showed that organic manure significantly increased the total number of fungi, actinomyces, bacteria, P solubilizing bacteria, organic P mineralizing bacteria, P solubilizing rate and organic P mineralizing rate, soil respiration rate, and selected enzyme activities, whereas chemical fertilizer resulted in a smaller effect, and bacteria were affected more than fungi and actinomyces by organic manure. The enhancement of biological activities caused by organic manure might be due to the introduction of a large amount of living microorganisms and readily‐utilizable carbon source on which microorganisms live. This study showed that the augment of inorganic phosphate solubilizing bacteria and organic P mineralizing bacteria was one of the reasons that organic manure increased the avilability of P in a blue purple paddy soil.     

The interactive effects of biochar and cow manure on rice growth and selected properties of salt-affected soil

Salt-affected soil induces detrimental influences on paddy rice (Oryza sativa L.) growth and ameliorating the influences could be done with organic amendments, such as animal manure and biochar. The aims of the current study are: (1) to examine the interactive effects of biochar and cow manure on rice growth and on selected properties of salt-affected soil, and (2) to identify potential mechanisms related to the amendments. Saline-sodic soil was used for a net house experiment with two experimental factors: biochar (no-biochar, rice-husk, and -straw biochar) and cow manure (with and without cow manure). Without the manure, addition of both rice-hush and – straw biochar significantly increased rice growth, whereas a combination of individual biochar with manure did not show a positive synergistic effect. The interactive effect of two factors was not significant on available P and exchangeable K concentrations, but the main effects of the two factors were significant. Biochar addition resulted in higher soil cation exchange capacity (CEC) (28.8 to 29.0 cmol_c kg^?1) than the control (25.6 cmol_c kg^?1), but manure addition did not. Improved nutrient availabilities such as P and K, as well as CEC are among the potential mechanisms accounting for the enhanced rice growth with biochar.     

Short-term mesofauna responses to soil additions of corn stover biochar and the role of microbial biomass

Biochar additions have been suggested to influence soil microbial communities that, through a cascade effect, may also impact soil fauna. In turn, any direct biochar effects on fauna can influence microbial communities through grazing, physical fragmentation of organic debris (and biochar) and modifying soil structure. If biochar creates a favorable environment for soil microorganisms, it is also plausible for fauna to be attracted to such microbially enriched habitats. However, how soil fauna respond to biochar addition to soil and what are the main factors that drive their behavior has rarely been experimentally addressed. Therefore, the behavior of two mesofauna species was assessed as a result of corn stover biochar (slow pyrolysis at 600 °C) additions to a loamy temperate soil, after preincubation for 2, 17, 31 and 61 d, and related to variations in microbial biomass and activity. Microbial biomass increased by 5–56% and activity by 6–156% with increasing biochar rates for the different preincubation times. Over the incubation time, microbial biomass did not change or increased at most 15% with the different biochar rates, while in turn microbial activity decreased steadily (around 70–80% at day 61). Enchytraeids generally did not show avoidance or preference to biochar when provided with an alternative unamended soil, while collembolans often showed avoidance responses. However, collembolan avoidance to biochar decreased or disappeared in biochar mixtures with higher microbial biomass and water extractable NH₄-N content, agreeing with the plausible role of microorganisms to potentially attract soil fauna after biochar applications. Avoidance response was mainly explained by environmental preferences of the test species and not by any toxic effect of the biochar in this study. However, avoidance after the application of biochar may still need to be considered due to the potential negative impacts of individuals’ migration on soil ecosystem functioning.     

Effects of biochar,earthworms, and litter addition on soil microbial activity and abundance in a temperate agricultural soil

Biochar application to arable soils could be effective for soil C sequestration and mitigation of greenhouse gas (GHG) emissions. Soil microorganisms and fauna are the major contributors to GHG emissions from soil, but their interactions with biochar are poorly understood. We investigated the effects of biochar and its interaction with earthworms on soil microbial activity, abundance, and community composition in an incubation experiment with an arable soil with and without N-rich litter addition. After 37 days of incubation, biochar significantly reduced CO₂ (up to 43 %) and N₂O (up to 42 %), as well as NH₄ ⁺-N and NO₃ ^?-N concentrations, compared to the control soils. Concurrently, in the treatments with litter, biochar increased microbial biomass and the soil microbial community composition shifted to higher fungal-to-bacterial ratios. Without litter, all microbial groups were positively affected by biochar × earthworm interactions suggesting better living conditions for soil microorganisms in biochar-containing cast aggregates after the earthworm gut passage. However, assimilation of biochar-C by earthworms was negligible, indicating no direct benefit for the earthworms from biochar uptake. Biochar strongly reduced the metabolic quotient qCO₂ and suppressed the degradation of native SOC, resulting in large negative priming effects (up to 68 %). We conclude that the biochar amendment altered microbial activity, abundance, and community composition, inducing a more efficient microbial community with reduced emissions of CO₂ and N₂O. Earthworms affected soil microorganisms only in the presence of biochar, highlighting the need for further research on the interactions of biochar with soil fauna.     

生物黑炭对玉米苗期根际土壤氮素形态及相关微生物的影响

生物黑炭被作为土壤改良剂应用逐渐被认可,但其应用机制特别是生物黑炭对氮素形态和根际微生物的影响机理尚不明确,影响其推广。本文采用盆栽试验,研究了玉米和水稻秸秆烧制的生物黑炭按不同量施入土壤后,对玉米苗期株高、生物量和根际土壤氮素形态及相关微生物的影响。结果表明,施入60 g·kg-1玉米黑炭和40~60 g·kg-1水稻黑炭均对玉米苗期株高有显著(P0.05)降低作用,其中水稻黑炭的降低效果更为明显;分别施入60 g·kg-1玉米黑炭和20~60 g·kg-1水稻黑炭后,玉米植株地上部生物量均显著降低。施入60 g·kg-1玉米黑炭后根际土壤含水量和微生物量氮显著提高。随两种生物黑炭施入量的不断增加,玉米苗期根际土壤全氮、硝态氮含量以及固氮作用强度也显著增加,且均在60 g·kg-1施用量下达最大值。施用40 g·kg-1玉米黑炭可显著提高玉米苗期根际土壤氨态氮含量。同时,施用两种生物黑炭后,均不同程度地抑制了玉米根际土壤中细菌总体数量,促进了固氮菌和纤维素降解菌的生长,其中施入60 g·kg-1玉米黑炭的效果最为明显。综上,玉米和水稻秸秆生物黑炭的适量施用,可以促进玉米根际土壤氮素的循环转化,影响相关微生物的群落结构,且与水稻秸秆相比,玉米秸秆生物黑炭的施用效果更加明显。本文针对作物生长、土壤氮素形态及相关微生物数量3个方面研究生物黑炭施入土壤对氮有效性的影响,能够更全面、更准确地将生物黑炭如何影响土壤氮素转化展现出来,促进生物黑炭的深入开发利用,对黑土肥力保护具有一定意义。     

Effect of biochar application on mineral and microbial properties of soils growing different plant species

Biochar is widely used as a soil amendment to increase crop yields. However, the details of its impact on soil properties have not been fully understood. A pot experiment was conducted using soybean (Glycine max (L.) Merr. cv. Toyoharuka) and sorghum (Sorghum bicolor (L.) Moench cv. Hybrid Sorgo) under four soil treatment combinations (cattle farmyard manure with or without biochar and rapeseed cake with or without biochar) to elucidate the mechanisms of its beneficial effects on plant growth in terms of the microbial community structure and mineral availability in soils with different types of organic manure application. The application of biochar significantly increased the growth of both species, particularly sorghum with rapeseed cake application by 1.48 times higher than that without biochar. Microbial activity in soil was also enhanced by biochar application in both species with rapeseed cake application, particularly in sorghum. Principal component analysis using Biolog EcoPlate^TM data indicated that biochar application changed the microbial community structure in soil, particularly sorghum-grown soil. The changes in microbial community structure in sorghum were considered to be at least partly affected by changes in soil pH due to interaction between plant and biochar under organic manure application. Biochar application had little effect on the profile of ammonium-acetate-extractable mineral elements in soil including calcium, potassium, magnesium, sodium and sulfur with both types of manure application under soybean. Under sorghum, however, biochar with rapeseed cake manure application altered the profile. This alteration is attributable to an increase in the extractable concentration of certain metals in the soil including aluminum, cadmium and zinc, possibly caused by enhanced organic matter decomposition producing metal-chelating organic compounds. These different changes in the soil properties by biochar application may be directly or indirectly related to the different growth responses of different plant species to biochar application under organic manure application.     

Co-application of sugarcane bagasse biochar,farmyard manure and mineral nitrogen improved growth indices of corn grown in alkaline calcareous soil

Abstract

Soil quality and crop productivity can be improved by the combined soil application of organic amendments and synthetic fertilizers. We evaluated the sole and combined effects of sugarcane-bagasse biochar (SBB), farmyard manure (FYM) and nitrogen (N) fertilizer on soil properties and corn yield traits. Three N fertilizer rates (0, 50 and 100% of recommended) were used with or without the organic amendments. We observed significant increases in soil nitrate-N (at vegetative and reproductive phases), ammonical-N and microbial-biomass-N contents in responses to a co-application of 0.5% SBB, 0.5% FYM and 100% N fertilizer (p?≤?0.05). While the same co-application also resulted in the most significant soil organic carbon value, the maximum soil microbial biomass carbon was observed when 0.5% SBB and 0.5% FYM combination was applied along with 50% N fertilizer (p?≤?0.05). Plant growth indices—shoot length and, fresh and dry weights of shoot and root were also recorded to be the highest where the same organic amendments were applied in addition to a 50% or 100% mineral N fertilizer (p?≤?0.05). Combined application of the organic amendments effectively improved soil CEC compared to those in responses to individual applications of SBB and FYM (p?≤?0.05). Conclusively, for increasing the corn yield and improving the soil quality, the co-application of 0.5% SBB and 0.5% FYM was more effective than any of the individual 1% applications; Additions of 50% and 100% mineral N to the organic combination were equally useful for increasing the grain yield.     

Effects of Biochar and Phosphorus Fertilizers on Phosphorus Fractions,Wheat Yield and Microbial Biomass Carbon in Vertic Torrifluvents

The present work was carried out to investigate the effect of biochar and phosphorus (P) fertilizer application, on phosphorus fractions, soil microbial biomass carbon in a Vertisol during two seasons for wheat in field experiments. Phosphorus was added at 0%, 50%, 100% and 150% P of recommended P fertilizers, with or without biochar at a rate of 10 t h^?1 arranged in a randomized complete block design with three replicates. Results showed that the wheat grain yield increased by 56% to 69% in plots treated with the interaction of biochar and P mineral during the 2015 and 2016 growing seasons. Co-application of biochar with inorganic P produced up to 1.5 fold more microbial biomass C than either biochar or inorganic P applied alone. Sequential extraction of the biochar-treated with P revealed that HCl-P decreased, whereas others fractions increased with increasing P rate. The inorganic and organic P fractions were increased significantly when the biochar was combined with fertilizer P as compared to the biochar or inorganic P applied alone. The results of this study reveal that the co-application of biochar with inorganic P can be a promising strategy to improve soil productivity and soil quality in alkaline soil.     

Manure application followed by biochar application increases plant production regardless of soil dehydrogenase activity

Biochar is obtained by the pyrolysis of biomass, and contains abundant carbon and minerals. Biochar supplementation of soils can greatly improve soil health and quality, but these beneficial effects typically develop slowly over time. Depending on the quality of the biochar and the soil to which it is applied, it may take years before positive effects are apparent. This is because organic substances are slowly sorbed onto the biochar over time, and the biochar eventually becomes part of the sorption complex of the soil. It is therefore advisable to apply biochar together with some organic material. We examined the effect of co-application of different doses of biochar with manure on soil dehydrogenase activity (DHA), soil oxidizable carbon (COX), cumulative soil respiration, soil buffering capacity, the soil exchange reaction (pH/KCl) and the production yield of winter rape seeds. We also determined seed production when artificial granular fertilizers were added to biochar and manure. The results showed that the application of biochar and manure significantly increased grain yield, DHA, the soil exchange reaction and cumulative respiration. Thus, application of biochar with organic material can increase seed yield and some properties of agricultural soils. However, the positive effect of biochar on seed yield was not directly proportional to biochar dose, in that the seed yield was lower for a biochar dose of 45 t/ha than 30 t/ha.     

Effects of compost,biochar and manure on carbon mineralization of biogas residues applied to soil

Biogas residues contain microbial biomass, which contributes to the formation of soil organic matter. Whether the potential of biogas residues to increase soil organic matter can be enhanced by co‐application with compost, biochar or manure is unknown, however. The aim of this paper is to evaluate the effects of co‐amendment on the mineralization of biogas residues, carbon dioxide emissions and the carbon flow within the microbial food web. We determined the fate of ¹³C‐labelled microbial biomass present in biogas residues applied together with compost, biochar and manure to soil, by analysing CO₂ and biomarker phospholipid fatty acids. Although the rate of mineralization constant of the slowly degrading carbon pool was not affected by co‐amendments, co‐amendment with manure resulted in a larger rate of mineralization constant of the readily degrading carbon pool of biogas residues. The incorporation of carbon was mainly to Gram‐negative biomass and was the smallest with manure co‐amendment, which indicated differences in bioavailability of the carbon source.     

The influence of mineral and organic fertilisers on the growth of the endogeic earthworm Octolasion tyrtaeum (Savigny)

Endogeic earthworms play an important role in mobilisation and stabilisation of carbon and nitrogen in forest and arable soils. Soil organic matter is the major food resource for endogeic earthworms, but little is known about the size and origin of the organic matter pool on which the earthworms actually live. We measured changes in body mass of juvenile endogeic earthworms, Octolasion tyrtaeum (Savigny), in soils with different C and N contents resulting from different fertiliser treatments. The soil was taken from a long-term experiment (Statischer Düngungsversuch, Bad Lauchstädt, Germany). The treatments included (1) non-fertilised soil, (2) NPK fertilised soil, (3) farmyard manure fertilised soil and (4) NPK + farmyard manure fertilised soil. The soil was incubated in microcosms with and without one juvenile O. tyrtaeum for 80 days.Earthworm biomass decreased in non-fertilised soil by 48.6%, in NPK soil by 9.4%, but increased in farmyard manure soil by 19.7% and 42.8% (soil with additional NPK application). In farmyard manure treatments the biomass of bigger individuals decreased, but in smaller individuals it increased. In NPK fertilised soil without farmyard manure only small O. tyrtaeum increased in body mass, whereas in the non-fertilised soil all individuals decreased in body mass. Generally, soil respiration correlated positively with soil carbon content. Earthworms significantly increased soil respiration and nitrogen leaching and this was most pronounced in farmyard manure treatments. Microbial activity was generally higher in farmyard manure soil indicating that farmyard manure increases labile organic matter pools in soil. Also, biomass of earthworms and microorganisms was increased in farmyard manure soil. The presence of earthworms reduced microbial biomass, suggesting that earthworms feed on microorganisms or/and that earthworms and soil microorganisms competed for similar organic matter pools in soil. The results demonstrate that NPK fertilisation only is insufficient to sustain O. tyrtaeum, whereas long-term fertilisation with farmyard manure enables survival of endogeic species due to an increased pool of utilisable soil organic matter in arable soil.     

生物炭用量对塿土微生物量及碳源代谢活性的影响

目的研究果树树干、枝条制成的生物炭添加4～5年后,其添加量对土微生物量及碳源代谢活性的影响,为生物炭改良土的合理应用提供数据支撑和理论依据。方法基于陕西关中土的长期田间试验,采用氯仿熏蒸—浸提法及Biolog-ECO检测法,研究了生物炭不同添加量 (0、20、40、60、80 t/hm2) 下冬小麦不同生育期土壤微生物量C、N、P、C/N的动态变化及土壤微生物的碳源代谢活性。结果当生物炭添加量为40～60 t/hm2时,显著提高了土壤微生物量碳;当生物炭添加量 ≥ 40 t/hm2时,显著提高了土壤微生物量C/N;添加生物炭对土壤微生物量N、P没有显著影响。当生物炭添加量为20 t/hm2时,显著增加了土壤微生物量碳的季节波动;当生物炭添加量为40～60 t/hm2时,显著增加了土壤微生物量C/N的季节波动;当生物炭添加量为20～60 t/hm2时,显著降低了土壤微生物量P的季节波动;添加生物炭对土壤微生物量N的季节波动没有显著影响。添加生物炭对土壤微生物碳源代谢活性没有显著影响,但高量生物炭的添加有降低土壤微生物整体代谢活性的趋势。当生物炭添加量为60 t/hm2时,显著降低了土壤丰富度指数,显著提高了均匀度指数;当生物炭添加量 ≥ 60 t/hm2时,显著降低了Shannon-Wiener指数、Simpson指数。添加生物炭对土壤微生物利用糖类、氨基酸类、多聚物类、多酚化合物类、多胺类碳源的利用率没有显著影响,但生物炭添加量为60 t/hm2时,土壤微生物显著降低了对羧酸类碳源的利用率;糖类、羧酸类、氨基酸类是土中微生物比较偏好、利用率较高的碳源。结论生物炭添加4～5年后,在第7季作物冬小麦生育期内,其不同添加量对土壤微生物量及微生物功能多样性的影响依然有显著的差异。生物炭添加量为40 t/hm2时,可以显著提高土壤微生物量碳和C/N,显著降低土壤微生物量磷的季节波动;生物炭添加量大于40 t/hm2时,土壤微生物的整体代谢活性,表征土壤微生物功能多样性的丰富度指数、Shannon-Wiener指数、Simpson指数,土壤微生物对糖类、氨基酸类、多胺类碳源的利用率均呈现降低趋势。因此,生物炭添加量必须控制在合理的范围内,避免对土壤产生不良影响。     

Inoculation of wheat with Azospirillum brasilense and Pseudomonas fluorescens: Impact on the production and culturable rhizosphere microflora

Scientific evidence recognizes that the operation of a terrestrial ecosystem depends on soil microbial activity. Some Azospirillum strains produce plant growth regulators, increase the development of roots, and fix atmospheric nitrogen (N₂). Some Pseudomonas strains are capable of producing cytokinins and solubilizing organic phosphorus. A sustainability analysis requires a detailed knowledge of the interrelationships between the microorganisms added to the system and those present in the soil. This study examines the effect of three commercial inoculants Azospirillum brasilense Az1 and Az2 as well as Pseudomonas fluorescens Pf on biomass production, grain yield and rhizosphere colonization of wheat, combined with two levels of N-addition. Plate counts of rhizosphere soil showed that the inoculation and N-addition did not affect the number of P. fluorescens, whereas it significantly affected the number of Azospirillum. N-addition and inoculation did not change the communities of actinomycetes and bacteria but they changed the number of fungi at the rhizosphere of wheat plants. Community-level physiological profiles of carbon-source utilization of rhizosphere soil microbial communities were changed after inoculation with Az1, Az2 and Pf depending on the phenological stage of the crop. Although no significant responses were observed, in average, PGPB inoculation increased aerial biomass by 12%, root biomass by 40% and grain yield by 16%. These increases represent important earnings for the farmer and they may help to obtain a greater sustainability of the agroecosystems.     

生物炭配施氮肥改善表层土壤生物化学性状研究

【目的】 探讨生物炭配施氮肥对土壤碳氮、生物学性质及春玉米产量的影响,阐明生物炭配施氮肥后,土壤碳氮含量及生化性质变化规律,旨在为合理培肥、改善土壤环境、增加春玉米产量提供科学依据。 【方法】 在内蒙古西部 (包头) 和东部 (通辽) 2个试验点进行大田试验,设生物炭用量0、8、16、24 t/hm2 4个水平 (分别记作C₀、C₈、C₁₆、C₂₄) ,设施氮量 0、150、300 kg/hm2 3个水平 (分别记作N₀、N₁₅₀、N₃₀₀) ,于成熟期测产,并于收获后分3个土层 (0—10 cm、10—20 cm、20—40 cm) 测定土壤碳氮含量、微生物量及酶活性。 【结果】 生物炭和氮肥对2个试验点0—10 cm、10—20 cm和20—40 cm土层有机碳、碳氮比、微生物量及酶活性均有极显著影响 (P < 0.01) ,且两者交互作用极显著。3个土层有机碳含量以及0—10 cm和10—20 cm土层全氮含量在各施氮水平随生物炭施用量的增加而增加。施加生物炭和氮肥均能显著提高3个土层的微生物量碳、微生物量氮、蔗糖酶活性、脲酶活性以及总体酶活参数,且随炭、氮施入量的增加呈先增后减的趋势;施用生物炭后0—10 cm和10—20 cm土层的微生物量碳、微生物量氮以及蔗糖酶、脲酶活性均显著高于20—40 cm土层。生物炭配施氮肥可显著提高春玉米穗粒数、百粒重及产量,2试验点产量均以C ₈N₁₅₀最大,包头和通辽分别为15.51 t/hm2和16.43 t/hm2。通过相关分析可知,春玉米产量主要与0—10 cm和10—20 cm土层的微生物量及酶活性有关。 【结论】 适量生物炭配施氮肥能够增加土壤碳氮储量、微生物量和酶活性,改善土壤微生态环境。炭氮配施能够提高土壤肥力,减少氮肥用量,本试验中以8 t/hm2生物炭配施150 kg/hm2氮肥为最佳施肥量。      

Phosphate solubilizing microorganisms isolated from rhizosphere of maize cultivated in an oxisol of the Brazilian Cerrado Biome

Many soil microorganisms are able to transform insoluble forms of phosphorus to an accessible soluble form, contributing to plant nutrition as plant growth-promoting microorganisms (PGPM). The objective of this work was to isolate, screen and evaluate the phosphate solubilization activity of microorganisms in maize rhizosphere soil to manage soil microbial communities and to select potential microbial inoculants. Forty-five of the best isolates from 371 colonies were isolated from rhizosphere soil of maize grown in an oxisol of the Cerrado Biome with P deficiency. These microorganisms were selected based on the solubilization efficiency of inorganic and organic phosphate sources in a modified Pikovskaya's liquid medium culture containing sodium phytate (phytic acid), soybean lecithin, aluminum phosphate (AlPO₄), and tricalcium phosphate (Ca₃(PO₄)₂). The isolates were identified based on nucleotide sequence data from the 16S ribosomal DNA (rDNA) for bacteria and actinobacteria and internal transcribed spacer (ITS) rDNA for fungi. Bacteria produced the greatest solubilization in medium containing tricalcium phosphate. Strains B17 and B5, identified as Bacillus sp. and Burkholderia sp., respectively, were the most effective, mobilizing 67% and 58.5% of the total P (Ca₃(PO₄)₂) after 10 days, and were isolated from the rhizosphere of the P efficient L3 maize genotype, under P stress. The fungal population was the most effective in solubilizing P sources of aluminum, phytate, and lecithin. A greater diversity of P-solubilizing microorganisms was observed in the rhizosphere of the P efficient maize genotypes suggesting that the P efficiency in these cultivars may be related to the potential to enhance microbial interactions of P-solubilizing microorganisms.     

Long-term alternative dairy manure management approaches enhance microbial biomass and activity in perennial forage grass

Removing solids from liquid dairy manure slurry reduces manure phosphorus (P) and increases the available (mineral) fraction of nitrogen (N) but also decreases the organic matter content of the manure. While this novel treatment reduces environmental concerns associated with excess N and P application to soils, it may also reduce microbial biomass and activity in soil. This study evaluated the long-term effects of this alternative manure treatment compared to more typical nutrient applications in a perennial grass sward (tall fescue, Festuca arundinacea Schreb.) on soil microbial biomass, community composition, hydrolytic enzyme activity, and forage yield. Nutrient treatments for this long-term field experiment in Agassiz, British Columbia, Canada were started in 2003. The treatments included liquid dairy manure slurry, liquid dairy manure with solids removed, commercial fertilizer, a combination of fertilizer and dairy manure, and a control. All treatments were applied at 400–600 kg total N ha^?1 year^?1 in four equal doses. Soil microbial community composition (phospholipid fatty acid analysis) and activity (hydrolytic enzyme activity) were determined several times during the 2013 and 2014 growing seasons to a depth of 15 cm. Time of sampling (date) had a strong influence on microbial biomass, community composition, and activity, while the response to soil properties and yield was more varied. All manure treatments (dairy manure slurry, liquid fraction, and the combination) increased microbial biomass (by 19–32%) and the potential activity of cellulose-degrading enzymes (by 31–47%) compared to commercial fertilizer and unamended plots. The commercial fertilizer and liquid fraction lowered fungal/bacterial ratios compared with both whole manure and unamended plots. Our results indicate that separating the solid from the liquid fraction of manure, to improve crop yield and reduce P loading, did not reduce microbial community size and activity and that all manure treatments increased microbial biomass and activity compared to mineral fertilizer application.     

生物炭对铜矿区污染土壤微生物活性及香根草富集铜、镉、铅的影响

矿区土壤易发生重金属污染,是土地资源利用和维护的一大难题。以铜矿区污染土壤为研究对象,按质量比添加0,1%,2%,4%,10% (w/w)的生物炭,进行香根草室内盆栽试验。研究添加生物炭对土壤pH和微生物活性、香根草富集与转运重金属的影响,探明重金属形态含量与生物炭、微生物活性的相关性,旨在为生物炭与香根草联合修复矿区重金属污染土壤提供理论参考。结果表明:生物炭的添加能提高土壤pH,显著提高土壤FDA水解酶、蔗糖酶和脲酶活性,显著促进土壤基础呼吸,但对土壤微生物量碳无显著影响;生物炭的添加使香根草生物量显著增大,降低土壤Cu和Pb的有效态占比,Cd的变化与此相反;添加生物炭促进香根草对Cd和Pb的富集,降低香根草对Cu的富集,减少Cu、Cd和Pb在香根草体内的转运,因此香根草可作为Cu、Cd和Pb的稳定化植物。土壤蔗糖酶活性与香根草叶片Cu、Cd和Pb含量、有效态和残渣态Cu含量呈显著正相关,土壤基础呼吸与叶片Cu、Cd和Pb含量、有效态Cu、Pb含量呈显著负相关,而与有效态Cd含量呈显著正相关。总之,生物炭可减弱矿区土壤重金属对香根草生长的毒害作用,并促进香根草对重金属的富集,两者结合可改善铜矿区污染土壤的理化性质和微生物活性,有利于重金属污染土壤修复,改善土壤质量。