Liming reduces soil phosphorus availability but promotes yield and P uptake in a double rice cropping system

Liming is often applied to alleviate soil acidification and increase crop yield on acidic soils,but its effect on soil phosphorus(P)availability is unclear,particularly in rice paddies.The objective of this study was to examine the effect of liming on rice production,yield and P uptake in a three-year field experiment in a double rice cropping system in subtropical China.We also conducted an incubation experiment to investigate the direct effect of liming on soil available P and phosphatase activities on paddy soils in the absence of plants.In the incubation experiment,liming reduced soil P availability(measured as Olsenextractable P)by 14–17%and inhibited the activity of soil acid phosphatase.Nonetheless,lime application increased grain yield,biomass,and P uptake in the field.Liming increased grain yield and P uptake more strongly for late rice(26 and 21%,respectively)than for early rice(15 and 8%,respectively).Liming reduced the concentration of soil available P in the field as well,reflecting the increase in rice P uptake and the direct negative effect of liming on soil P availability.Taken together,these results suggest that by stimulating rice growth,liming can overcome direct negative effects on soil P availability and increase plant P uptake in this acidic paddy soil where P is not the limiting factor.

Phosphorus availability in two soils amended with poultry litter

Understanding P transformation in soils amended with poultry litter is important if water quality is to be protected.Our objectives were to determine the influence of method of litter application and temperature on P availability. Poultry litter containing 20. 8g P/kg (dry weight) was either surface-applied or incorporated into Captina (fine-silty, siliceous, mesic Typic Fragiudult) and Nixa (loamy-skeletal,siliceous,Glossic Fragiudult) silt loams at rates of 0 or 10g/kg and incubated at 20℃ or 35℃ at a water potential of -40 kpa. Water soluble and available P (0.03 mol/L NH4F+0. 025mol/L HCl extraction) were determined during a 60d laboratory study. Results indicated that water soluble and available P levels in the soils initially decreased, then rapidly increased,and approached a steady state phase after approximately 20d. After 60d, water soluble P levels were significantly higher when litter was surface applied than when litter was incor porated. When the incubation was terminated, the net increase in available P in both soils was>100 mg P/kg.For efficient recycling of P and protection of water quality, application method and temperature should be considered when amending soils with poultry litter,

Combining field data and modeling to better understand maize growth response to phosphorus(P) fertilizer application and soil P dynamics in calcareous soils

We used field experimental data to evaluate the ability of the agricultural production system model (APSIM) to simulate soil P availability,maize biomass and grain yield in response to P fertilizer applications on a fluvo-aquic soil in the North China Plain.Crop and soil data from a 2-year experiment with three P fertilizer application rates(0,75 and 300 kg P_(2)O_(5) ha^(–1)) were used to calibrate the model.Sensitivity analysis was carried out to investigate the influence of APSIM SoilP parameters on the simulated P availability in soil and maize growth.Crop and soil P parameters were then derived by matching or relating the simulation results to observed crop biomass,yield,P uptake and Olsen-P in soil.The re-parameterized model was further validated against 2 years of independent data at the same sites.The re-parameterized model enabled good simulation of the maize leaf area index (LAI),biomass,grain yield,P uptake,and grain P content in response to different levels of P additions against both the calibration and validation datasets.Our results showed that APSIM needs to be re-parameterized for simulation of maize LAI dynamics through modification of leaf size curve and a reduction in the rate of leaf senescence for modern staygreen maize cultivars in China.The P concentration limits (maximum and minimum P concentrations in organs)at different stages also need to be adjusted.Our results further showed a curvilinear relationship between the measured Olsen-P concentration and simulated labile P content,which could facilitate the initialization of APSIM P pools in the NCP with Olsen-P measurements in future studies.It remains difficult to parameterize the APSIM SoilP module due to the conceptual nature of the pools and simplified conceptualization of key P transformation processes.A fundamental understanding still needs to be developed for modelling and predicting the fate of applied P fertilizers in soils with contrasting physical and chemical characteristics.

Influence of phosphorus availability on the community structure and physiology of cultured biofilms

Biofilms have important effects on nutrient cycling in aquatic ecosystems.However,publications about the community structure and functions under laboratory conditions are rare.This study focused on the developmental and physiological properties of cultured biofilms under various phosphorus concentrations performed in a closely controlled continuous flow incubator.The results showed that the biomass（Chl a）and photosynthesis of algae were inhibited under P-limitation conditions,while the phosphatase activity and P assimilation rate were promoted.The algal community structure of biofilms was more likely related to the colonization stage than with the phosphorus availability.Cyanobacteria were more competitive than other algae in biofilms,particularly when cultured under low P levels.A dominance shift occurred from non-filamentous algae in the early stage to filamentous algae in the mid and late stages under P concentrations of 0.01,0.1 and 0.6 mg/L.However,the total N content,dry weight biomass and bacterial community structure of biofilms were unaffected by phosphorus availability.This may be attributed to the low respiration rate,high accumulation of extracellular polymeric substances and high alkaline phosphatase activity in biofilms when phosphorus availability was low.The bacterial community structure differed over time,while there was little difference between the four treatments,which indicated that it was mainly affected by the colonization stage of the biofilms rather than the phosphorus availability.Altogether,these results suggested that the development of biofilms was influenced by the phosphorus availability and/or the colonization stage and hence determined the role that biofilms play in the overlying water.

Soil phosphorus fractions and their availability over natural succession from clear-cut of a mixed broadleaved and Korean pine forest in northeast China

To assess phosphorus(P)status of forest soil under naturally restored vegetation,P fractions in the 10-cm soil layer were quantified at different successional stages on the clear-cut site of mixed broadleaved and Korean pine forest.Four communities of shrub,softwood broad-leaved forest,softwood and hardwood broad-leaved forest,and hardwood broad-leaved forest represented different successional stages.A soil sample from a primary broad-leaved and Korean pine stand was the control.A sequential P fractionation scheme extracted empirically defined pools of P and path analysis used to partition the direct and indirect contribution of soil P fractions to available P.The results show that available P increased significantly with long-term succession,while both sodium bicarbonate-extractable P(NaHCO_(3)-P)and sodium hydroxide-extractable P(NaOHP)fractions were reduced in early successional stages and increased in late stages.Compared to the primary forest,concentrations of P fractions in the four stages significantly decreased except for HCl-P,indicating that soil P supplements over the long-term did not return to primary forest levels.The results of related analysis also showed that NaHCO_(3)-P_(i)levels were significantly related to available phosphorus.According to the path analysis coefficient,NaHCO_(3)-P_(i)exhibited the highest effect on available P among eight P fractions;the indirect effects of other P fractions via NaHCO_(3)-P_(i)were larger than those with other P fractions.Overall,this study suggests that soil P bioavailability gradually improved during natural vegetation restoration on clear-cut sites mainly through the increase of NaHCO_(3)-P,where phosphorous is immediately available,and subsequently available phosphorus Na OH-P.

Effect of long-term fertilization on phosphorus fractions in different soil layers and their quantitative relationships with soil properties

Investigating the dynamics and distribution of soil phosphorus(P) fractions can provide a basis for enhancing P utilization by crops. Four treatments from a 29-year long-term experiment in black soil with maize cropping were involved in this study: no fertilizer(CK), inorganic nitrogen and potassium(NK), inorganic nitrogen, phosphorus, and potassium(NPK), and NPK plus manure(NPKM). We analyzed soil P fractions in different soil layers using a modified Hedley sequential method. The long-term NPKM treatment significantly increased total P by 0.6–1.6 times in the different soil layers. The Olsen-P concentration far exceeded the environmental threshold for soil Olsen-P(50.6 mg kg) in the NPKM treatment in the 0–60 cm soil profile. Moreover, the concentrations and proportion of labile and partially labile inorganic P(Pi) fractions(i.e., Na HCO-extracted Pi, Na OH-extracted Pi, and dilute HClextracted Pi) to the sum of all P fractions(Pt) in the 0–60 cm soil profile were higher in the NPKM treatment than in the NPK treatment, indicating that manure could promote the transformation of non-labile into more labile forms of P in soil, possibly by manure reducing P fixation by soil particles. Soil organic matter, Mehlich-3 extractable iron(Fe), and organic-bound aluminum were increased by fertilization, and were the main factors influencing the differences in the P fractions in the 0–20 cm soil layer. Soil mineral components, i.e., free Fe oxide and Ca CO, were the main factors influencing the P fractions in the subsoil. The soil P transformation process varied with soil layer and fertilization. Application of manure fertilizer can increase the labile(Olsen) P concentrations of the various soil layers, and thus should reduce the mineral P fertilizer requirement for crop growth and reduce potential environmental damage.

Critical Soil Phosphorus Values for Yield Reduction in Intensive Agricultural Systems

Phosphorus(P)is an essential element for agricultural production.Over-fertilization during decades caused an accumulation of P in soils leading to eutrophication in regions characterized by intensive agriculture.These environmental concerns together with the non-renewability of P resources have led to a more sustainable P use.Knowledge about the P need of crops is essential for a sustainable agriculture thereby minimizing P losses to the environment without lowering the yield substantially.Therefore,in this study,critical soil P values for yield reduction(PCrit)were determined based on fertilizer trials conducted between 1970 and 1988 and more recent fertilizer trials(2016-2017).At rotational level a common PCrit value of 109 mg P/kg dry soil(in an ammonium lactate and acetate extract)was determined.Crop specific PCrit values were also determined for seven crops(potato,winter wheat,barley,rye,maize,sugar beet and temporary grassland).These critical values ranged from 59 mg P/kg dry soil to 164 mg P/kg dry soil with winter wheat the least and maize the most sensitive towards P deficiency.The diversity in PCrit values among crops can mainly be explained by the root intensity but also rooting depth,exudation of organic acids and phosphatases may influence the PCrit value.The soil pH also influenced the P availability significantly.Soils with a favorable pH had a significantly higher availability(i.e.,lower PCrit value)for all crops compared to soils with a suboptimal pH.Critical soil P values might help to set up new or to evaluate current soil P in target zones used for P fertilizer recommendations.

Effects of Long-term Located Fertilization on Evolution of Available Phosphorus and Phosphorus Pool in Shandong Fluvo-aquic Soil

This study was conducted to investigate the effects of long-term located fertilization on soil phosphorus,the changes of soil available phosphorus（ OlsenP）,the evolution of soil total phosphorus（ TP） and the ratio change of Olsen-P to TP（ PAC） by 33-year fertilization experiments in winter wheat-summer maize rotation system in Shandong fluvo-aquic soil. Eight treatments were designed as no fertilization（ CK）,nitrogen fertilizer（ N）,nitrogen and phosphate fertilizer（ NP）,nitrogen and potassium fertilizer（ NK）,phosphate and potassium fertilizer（ PK）,nitrogen-phosphate-potassium fertilizer（ NPK）,reduced NPK fertilizer（ N（15） PK）,and increased NPK fertilizer（ N（25） PK）. Meanwhile,eight organic fertilizer-added treatments were designed based on the application of inorganic fertilizer the same as the above ones. The results showed that TP,Olsen-P and PAC of treatments added with organic fertilizer were higher than those without organic fertilizer,and those of the treatments applied with phosphate fertilizer were higher than those of no phosphate fertilizer. With the increase of years,soil P pool decreased due to crop absorption,nutrient loss and morphological transformation and other causes under the treatments of without and only phosphate fertilizer,while remained stable under the treatments added with organic fertilizer. The PAC values were generally lower in fluvo-aquic soil,and it could be improved by the application of organic fertilizer. On the whole,the application of chemical phosphate fertilizer combined with organic fertilizer could improve the phosphorus content in soil and ensure the supply of phosphorus nutrition. This study would provide scientific basis for fertilization management and soil fertility in fluvo-aquic soil.

The distribution and availability of phosphorus fractions in restored cut slopes soil aggregates:a case study of subalpine road,Southwest China

The distribution and availability of phosphorus(P)fractions in restored cut slope soil aggregates,along altitude gradients,were analyzed.Samples were collected at 3009,3347,3654 and 3980 m of altitude.We examined soil aggregates total phosphorus(TP),available phosphorus(AP)and phosphorus activation coefficient(PAC),and discovered that there was no significant difference in TP levels between all four altitudes samples(p>0.05).However,there was a significant difference in AP at 3009,3347 and 3980 m of altitude(p<0.05).At the altitudes of 3009,3347 and 3654 m,the AP accumulation in small size aggregates was more advantageous.Overall,PAC dropped steadily as soil aggregates sizes increased,as shown:PAC(3654 m)>PAC(3347 m)>PAC(3009 m)>PAC(3980 m).In all particle size soil aggregates,the distribution of the P fractions was as follows:total inorganic phosphorus(TPi)>total organic phosphorus(TPo)>residual phosphorus(R-P),at 3009,3347 and 3654 m,but a different registry was observed at 3980 m of altitude:TPo>TPi>R-P.Through correlation and multiple stepwise regression analysis,it was concluded that active NaHCO_(3)-Pi was the main AP source.It was also suggested that more attention should be given to the ratio of small particle size aggregates to increase soil AP storage.In order to improve the activation capacity and supply of soil P,along with promotion of the healthy development of soil ecosystem on slope land,it was suggest that inorganic P fertilizer and P activator could be added to soil at both low(3009 m)and high altitudes(3980 m).

Soil Organic Carbon Accumulation Increases Percentage of Soil Olsen-P to Total P at Two 15-Year Mono-Cropping Systems in Northern China

Soil organic carbon （SOC） and soil Olsen-P are key soil fertility indexes but information on their relationships is limited particularly under long-term fertilization. We investigated the relationships between SOC and the percentage of soil Olsen-P to total P （PSOPTP） under six different 15-yr （1990-2004） long-term fertilizations at two cropping systems in northern China. These fertilization treatments were （1） unfertilized control （control）; （2） chemical nitrogen （N）; （3） N plus chemical P （NP）; （4） NP plus chemical potassium （NPK）; （5） NPK plus animal manure （NPKM） and （6） high NPKM （hNPKM）. Compared with their initial values in 1989 at both sites, during the 1 lth to 15th fertilization years annual mean SOC contents were significantly increased by 39.4-47.0% and 58.9-93.9% at Gongzhuling, Jilin Province, and Urumqi, Xinjiang, China, under the two NPKM fertilizations, respectively, while no significant changes under the no-P or chemical P fertilization. During the 1 lth to 15th fertilization years, annual mean PSOPTP was respectively increased by 2.6-4.2 and 5.8-14.1 times over the initial values under the two chemical P fertilizations and the two NPKM fertilizations, but was unchanged in their initial levels under the two no-P fertilizations at both sites. Over the 15-yr long-term fertilization SOC significantly positively correlated with PSOPTP （r^2=0.55-0.79, P〈0.01）. We concluded that the combination of chemical P plus manure is an effective way to promote SOC accumulation and the percentage of soil Olsen-P to total P at the two mono-cropping system sites in northern China.

Regulating Effect of Exogenous Silicon on Soil Fertility in Paddy Fields

In order to explore the effects of different silicon preparations on the soil fertility of paddy fields,a pot experiment with Dongnong 427 was carried on.Different types of silicon preparations,including Si-50-G,Si-60-G,Si-RH,Si-50 and Si-60,were sprayed on the leaves of rice at the tillering stage,and CK was set in the control stage.The contents of alkali nitrogen,available phosphorus,available potassium and available silicon in soil were determined in the tillering stage,booting stage and maturity stage of rice.The results showed that spraying different silicon preparations at the tillering stage could promote the activation and release of soil available nutrients in different degrees.

How silicon fertilizer improves nitrogen and phosphorus nutrient availability in paddy soil?

In order to reveal the mechanism of silicon(Si)fertilizer in improving nitrogen(N)and phosphorus(P)nutrient availability in paddy soil,we designed a series of soil culture experiments by combining application of varying Si fertilizer concentrations with fixed N and P fertilizer concentrations.Following the recommendations of fertilizer manufacturers and local farmers,we applied Si in concentrations of 0,5.2,10.4,15.6,and 20.8μg/kg.At each concentration of added Si,the availability of soil N and P nutrients,soil microbial activity,numbers of ammonia-oxidizing bacteria and P-decomposing bacteria which means that the organic P is decomposed into inorganic nutrients which can be absorbed and utilized by plants,and urease and phosphatase activity first increased,and then decreased,as Si was added to the soil.These indicators reached their highest levels with a Si application rate of 15.6μg/kg,showing values respectively 19.78%,105.09%,8.34%,73.12%,130.36%,28.12%,and 20.15%higher than those of the controls.Appropriate Si application(10.4 to 15.6µg/kg)could significantly increase the richness of the soil microbial community involved in cycling of N and P nutrients in the soil.When the Si application rate was 15.6μg/kg,parameters for characterizing microbial abundance such as sequence numbers,operational taxonomic unit(OTU)number,and correlation indices of microbial community richness such as Chao1 index,the adaptive coherence estimator(ACE)index,Shannon index,and Simpson index all reached maximum values,with amounts increased by 14.46%,10.01%,23.80%,30.54%,0.18%,and 2.64%,respectively,compared with the control group.There is also a good correlation between N and P mineralization and addition of Si fertilizer.The correlation coefficients between the ratio of available P/total P(AP/TP)and the number of ammonia-oxidizing bacteria,AP/TP and acid phosphatase activity(AcPA),AP/TP and the Shannon index,the ratio of available N/total amount of N(AN/TN)and the number of ammoniated bacteria,and AN/TN and AcPA were 0.9290,0.9508,0.9202,0.9140,and 0.9366,respectively.In summary,these results revealed that enhancement of soil microbial community structure diversity and soil microbial activity by appropriate application of Si is the key ecological mechanism by which application of Si fertilizer improves N and P nutrient availability.

Application of a Soil Nutrient Measuring Instrument in Vegetable Seedling Substrate

[Objective] The aim was to find an efficient method to measure available nitrogen, phosphorus and potassium content in vegetable seedling substrate. [ Method] The suitable dosage of leaching agent, ratio of the substrate to water and leaching time for the detection of nutrient contents in the substrate by a soil nutrient measuring instrument were discussed firstly, and then the results of nutrient contents measured by the soil nutrient measuring instrument were compared with that by conventional approaches. [ Result] In compadson with the conventional methods, the av- erage content of available nitrogen measured by the soil nutrient measuring instrument was slightly higher, while the average content of available phosphorus measured by the instrument was lower; the average content of available potassium measured by the instrument was close to that by the conventional method. [ Conclusion] This study could provide us a new method to detect available nitrogen, phosphorus and potassium content in seedling substrate efficiently.

Activation Effect of Hydrochemical Energy in Regenerative Agriculture on Nutrients of Arsenic Sandstone

[Objectives]To study the activation effect of hydrochemical energy in regenerative agriculture on the nutrients of arsenic sandstone.[Methods]Starting from common environmental factors,moisture,it studied the mechanism of the release and activation of N,P,K nutrient elements in arsenic sandstone under different dry and wet environments.[Results]Water played a positive role in activating soil elements.Under the conditions of long-term dryness and alternating dry and wet conditions,the content of total nitrogen,available phosphorus and available potassium coexisted in the 210 d of culture and the element absorption and release,but the overall trend was increasing;under long-term flooding conditions,the content of total nitrogen and available potassium showed an overall increasing trend during the 210 d of culture,but the content of available phosphorus decreased.[Conclusions]Water plays a positive effect on activating soil elements.The research results are expected to provide a certain reference for the application research of water in regenerative agriculture.

Long-term biochar addition significantly decreases rice rhizosphere available phosphorus and its release risk to the environment

Phosphorus(P)availability,diffusion,and resupply processes can be altered by biochar addition in flooded rice rhizosphere,which controls the risk of P release to the environment.However,there are few in-situ investigations of these rhizospheric processes and effects.To explore the effects of biochar addition on soil P availability,high-resolution dialysis(HR-Peeper),diffusive gradients in thin films(DGT),and zymography techniques were used to provide direct evidence in the rice rhizosphere at the sub-millimeter scale.Long-term(9-years)field and greenhouse pot experiments demonstrated that biochar addition notably decreased the soluble/labile P and Fe concentrations in rice rhizosphere(vs.no biochar addition;CK)based on the results of Peeper,DGT,and two-dimensional imaging of labile P fluxes.DGT-induced fluxes in the soil/sediment(DIFS)model and sediment P release risk index(SPRRI)further indicated that biochar addition decreased the diffusion and resupply capacity of P from soil solid to the solution,thereby decreasing P release risk to the environment.These processes were dominated by Fe redox cycling and the hydrolysis of Al(hydro)oxides that greatly increased the unavailable P(Ca-P and residual-P).Additionally,greenhouse pot experiments(without additional biochar)showed that the previous long-term biochar addition significantly increased soil phosphatase activity,due to an adaptive-enhancing response to P decrease in the rhizosphere zone.The in-situ study on the biogeochemical reactions of P in the rice rhizosphere may provide a new and direct perspective to better evaluate the biochar addition and potential benefits to agricultural soils.

Phosphatase activity and culture conditions of the yeast Candida mycoderma sp. and analysis of organic phosphorus hydrolysis ability

Orthophosphate is an essential but limiting macronutrient for plant growth. About 67% cropland in China lacks sufficient phosphorus, especially that with red soil. Extensive soil phosphorus reserves exist in the form of organic phosphorus, which is unavailable for root uptake unless hydrolyzed by secretory acid phosphatases. Thus, many microorganisms with the ability to produce phosphatase have been exploited. In this work, the activity of an extracellular acid phosphatase and yeast biomass from Candida mycoderma was measured under different culture conditions, such as pH, temperature, and carbon source. A maximal phosphatase activity of 8.47 × 10^5±0.11× 10^5 U/g was achieved by C. Mycoderma in 36 hr under the optimal conditions. The extracellular acid phosphatase has high activity over a wide pH tolerance range from 2.5 to S.0 （optimum pH 3.5）. The effects of different phosphorus compounds on the acid phosphatase production were also studied. The presence of phytin, lecithin or calcium phosphate reduced the phosphatase activity and biomass yield significantly. In addition, the pH of the culture medium was reduced significantly by lecithin. The efficiency of the strain in releasing orthophosphate from organic phosphorus was studied in red soil （used in planting trees） and rice soil （originating as red soil）. The available phosphorus content was increased by 230% after inoculating 20 days in rice soil and decreased by 50% after inoculating 10 days in red soil. This work indicates that the yeast strain C. mycoderma has potential application for enhancing phosphorus utilization in plants that grow in rice soil.

Predicting phosphorus sorption isotherm parameters in soil using data of routine laboratory tests

Knowledge of phosphorus(P)sorption dynamics across different soil types could direct agronomic and environmental management of P.The objective of this study was to predict P isotherm parameters for a national soil population using data of routine laboratory tests.Langmuir and Freundlich sorption parameters were calculated from two different ranges(0-25 and 0-50 mg P L^(-1))using an archive of representative agricultural soil types from Ireland.Multiple linear regression(MLR)identified labile forms of aluminium(Al)and iron(Fe),organic matter(OM),cation exchange capacity(CEC),and clay as significant drivers.Langmuir and Freundlich sorption capacities,Freundlich affinity constant,and Langmuir buffer capacity were predicted reliably,with R^(2) of independent validation>0.9.Sorption isotherm parameters were predicted from P sorbed at a single concentration of 50 mg P L^(-1)(S_(50)).An MLR prediction of P sorption maximum in the 0-50 mg P L-1 range was achieved,to an accurate standard,using S_(50),OM,and Mehlich-3 Fe(R^(2) of independent calibration and validation being 0.91 and 0.95,respectively).Using Giles’four shapes of isotherms(C,L,H,and S),L non-strict-and C-shaped isotherm curves accounted for 64% and 27% of the soils,respectively.Hierarchical clustering identified a separation of isotherm curves influenced by two ranges of Mehlich-3 Al.Soils with a low range of Mehlich-3 Al(2.5-698 mg kg^(-1))had no incidence of rapid sorption(C shape).Single point indices,Al,or available soil data make the regression approach a feasible way of predicting Langmuir parameters that could be included with standard agronomic soil P testing.

Contribution of microbial phytases to the improvement of plant growth and nutrition: A review

Phytases belong to the class of phosphohydrolases that begin the step-wise hydrolysis of phosphates from phytates. Phytates are a derivative of myo-inositol, which is the primary storage form of organic phosphorus in plant cells. Phytase has been used globally to diminish phosphorus pollution and to enhance nutrition in monogastrics. In this review, the classification, sources, and diversity of microbial phytases, and their practical applications, as well as supplementation of the soil with transgenic and wild types of microbial strains, which can release phytase to enhance phosphorus availability for plant uptake and reduce the need for fertilizers, are discussed. The overexpressed microbial phytases in transgenic plants enhance the growth capacity of co-cultivated plants and can therefore be employed in agricultural and biotechnological practices, such as intercropping. The introduction of phytases into the soil for improved plant growth and enhanced crop yield can be accomplished without extra cost. A diverse group of photoautotrophic microalgae can synthesize phytase and will likely be useful in many human food and animal industries.

Fertilizer and soil conditioner value of broiler manure biochars

Pyrolysis is an option for enhancing the sustainable management of broiler manure surpluses by producing a concentrated,hygienic char product with a fertilizer and soil conditioner value.In this study,the impacts of pyrolysis conducted at 350,400 and 450℃ on total nutrient and harmful element concentrations in biochars derived from peat-bedded broiler manure were examined.Emphasis was placed on the availability of phosphorus(P).In addition,the pore structures of these biochars were explored using X-ray microtomography and image analysis.During pyrolysis,35-50%,40-55%and 35-45%of the original carbon,nitrogen and sulfur contents,respectively,of the feedstock biomass were lost as volatiles.Mineral elements,including P,were concentrated in the biochar.Although water-extractable P was found to be converted to less labile forms due to charring,the concentration effect and notable increase in sodium bicarbonate-extractable P rendered broiler manure biochars richer in total labile P in comparison with feedstock manure(7.1,10.0,11.1 and 14.8 g labile P kg^(−1)in feedstock and biochars produced at 350,400 and 450℃,respectively).The pore volume of the micrometer-scale porosity of the broiler manure biochar was comparable to that found earlier in wood-based biochars.In comparison with wood-based biochars,the pore structure of broiler manure biochars was more versatile,and the pore size distribution was wider.Consequently,part of the porosity was too large to store plant-available water,which may reduce the potential of broiler manure biochars to improve soil water storage capacity.

Effective alleviation of Cd stress to microbial communities in mining reclamation soils by thiourea-modified biochar amendment

Reclaimed soils in mining area usually display low fertility and present Cd stress.The amendment of modified biochar effectively fixes Cd in soils,enhances soil fertility,and reduces Cd stress in soil microorganisms.However,the effect of thiourea-modified biochar(TBC)on microbial adaptability to Cd stress in mining reclamation soils is still unclear.The present work studied the Cd immobilization and microbial community changes in a mining reclamation soil displaying extreme Cd contamination under TBC amendment.The results indicated that the amendment of TBC significantly enhanced(P<0.05)soil pH,the content of available phosphorus(AP),and the activities of urease and polyphenol oxidase by 1.3%,463.4%,54.4%,and 84.0%,respectively,compared to the control without amendment.The amount of toxicity characteristic leaching procedure-extracable Cd decreased(P<0.05)by 68.0%in the TBC-amended soil compared with the unamended soil.The structure of soil microbiota was reorganized and the alpha diversity index was increased in the TBC treatment.The TBC amendment increased the relative abundances of Proteobacteria,Bacteroidota,and Zoopagomycota,which were strongly associated(P<0.01)with higher soil pH and AP.Structural equation model results demonstrated that Cd immobilization was directly influenced by soil pH,AP,and urease,and indirectly affected by bacterial structure in the TBC treatment.The TBC amendment can effectively improve the structural composition of soil bacteria under Cd stress and enhance the pathways of decreasing soil Cd availability as well.The results might facilitate the development of in-situ remediation programs in Cd-contaminated soils in the future.