Towards predicting biochar impacts on plant-available soil nitrogen content

Biochars can improve soil health but have been widely shown to reduce plant-available nitrogen(N)owing to their high carbon(C)content,which stimulates microbial N-immobilization.However,because biochars contain large amounts of C that are not microbially available,their total elemental C:N ratio does not correspond well with impacts on soil N.We hypothesized that impacts on soil plant-available N would relate to biochar mineralizable-C(C_(min))content,and that C:N ratios of the mineralizable biochar component could provide a means for predicting conditions of net soil N-mineralization or-immobilization.We conducted two laboratory experiments,the first measuring biochar C_(min)from respiration of isotopically labeled barley biochars manufactured at 300,500,and 750℃,and the second characterizing C_(min)by proxy measurements for ten biochars from six feedstocks at several temperatures.For both experiments,soils were incubated with 2%biochar by mass to determine impacts to soil N-mineralization.Contrary to expectation,all the biochars increased soil N-mineralization relative to unamended soils.Also unexpected,higher temperature(500 and 700℃)barley biochars with less C_(min)stimulated more soil decomposition and more soil N-mineralization than a 350℃barley biochar.However,across diverse biochar feedstocks and production methods,none of the biochar characteristics correlated with soil N-mineralization.The finding of improved soil N-mineralization adds complexity to the range of soil N responses that can be expected in response to biochar amendment.Because of the limited ability to predict soil N responses from biochar properties,users should monitor soil N to manage soil fertility.

Feedstock choice,pyrolysis temperature and type influence biochar characteristics:a comprehensive meta-data analysis review

Various studies have established that feedstock choice,pyrolysis temperature,and pyrolysis type influence final biochar physicochemical characteristics.However,overarching analyses of pre-biochar creation choices and correlations to biochar characteristics are severely lacking.Thus,the objective of this work was to help researchers,biochar-stakeholders,and practitioners make more well-informed choices in terms of how these three major parameters influence the final biochar product.Utilizing approximately 5400 peer-reviewed journal articles and over 50,800 individual data points,herein we elucidate the selections that influence final biochar physical and chemical properties,total nutrient content,and perhaps more importantly tools one can use to predict biochar’s nutrient availability.Based on the large dataset collected,it appears that pyrolysis type(fast or slow)plays a minor role in biochar physico-(inorganic)chemical characteristics;few differences were evident between production styles.Pyrolysis temperature,however,affects biochar’s longevity,with pyrolysis temperatures>500℃ generally leading to longer-term(i.e.,>1000 years)half-lives.Greater pyrolysis temperatures also led to biochars containing greater overall C and specific surface area(SSA),which could promote soil physico-chemical improvements.However,based on the collected data,it appears that feedstock selection has the largest influence on biochar properties.Specific surface area is greatest in wood-based biochars,which in combination with pyrolysis temperature could likely promote greater changes in soil physical characteristics over other feedstock-based biochars.Crop-and other grass-based biochars appear to have cation exchange capacities greater than other biochars,which in combination with pyrolysis temperature could potentially lead to longer-term changes in soil nutrient retention.The collected data also suggest that one can reasonably predict the availability of various biochar nutrients(e.g.,N,P,K,Ca,Mg,Fe,and Cu)based on feedstock choice and total nutrient content.Results can be used to create designer biochars to help solve environmental issues and supply a variety of plant-available nutrients for crop growth.

Effects of grazing and precipitation variability on vegetation dynamics in a Mongolian dry steppe

Aims Grazing and water availability are the primary drivers of vegetation dynamics in grazing-dominated regions of Mongolia with a semi-arid climate and frequent droughts.Nomadic animal husbandry still plays a large part in the economy of Mongolia,but more variable precipitation regime and increase in livestock number have severely affected grassland ecosystems through overgrazing,leading to pasture degradation.This study aimed to examine the effects of grazing exclusion,interannual variation of plant-available precipitation(PAP)and their interaction on the aboveground biomass(AGB)of each dominant species,the AGB of annual species and the total AGB in a Mongolian dry steppe,using long-term field data.Methods To detect the effect of grazing on vegetation dynamics,vegetation surveys were conducted in a non-grazed exclosure zone and a fully grazed area outside the exclosure.We assessed the effects of grazing,PAP and their interaction on AGB parameters using a generalized linear model.A detrended correspondence analysis(DCA)was used to visualize the effects of grazing and PAP on the AGB of each species.Important Findings Grazing,PAP and their interaction had significant effects on AGB.The effect of grazing on AGB was larger with higher precipitation and higher amounts of AGB(i.e.forage)while AGB was strongly limited in drought years,which resulted in a smaller grazing effect.The current year PAP had the highest impact(r=0.88,P<0.01)on AGB.The dominance of annual species was characterized by the amount of PAP in the current and preceding years:annuals dominated in wet years that followed consecutive dry years.The DCA Axis 1 reflected the variation of AGB with interannual variation of PAP while the DCA Axis 2 differentiated the grazing effect.The DCA scatter diagram based on species score illustrated that Artemisia adamsii(an unpalatable herb)was clearly linked to grazing disturbance whereas palatable perennials such as Agropyron cristatum,Stipa krylovii and Cleistogenes squarrosa were related to grazing abandonment and wetter conditions.In brief,number of livestock,hence the grazing impacts on vegetation dynamic in this region could have driven by forage availability,which is mainly controlled by current-year PAP.

Soil micromorphological and physical properties after application of composts with polyethylene and biocomponent-derived polymers added during composting

Composts are considered to be one of the best soil amendments. However, the effects of composts with added polymeric materials on soil physical,hydraulic, and micromorphological properties have not been widely discussed. Changes in soil physical properties influence the numerous services that soils provide. We studied the impacts of composts with the addition of three different polymers(F1–F3) produced from polyethylene and thermoplastic corn starch on the physical, hydraulic, and micromorphological properties of two soils, a Cambic Phaeozem and a Luvic Phaeozem. Applying composts with polymers had limited or no significant effect on soil bulk density and porosity, but increased the field water capacity by 18%–82% and 3%–6% and the plant-available water content by 15%–23% and 4%–17% for the Cambic Phaeozem and Luvic Phaeozem, respectively. The application of composts with polymers had a greater effect on the Cambic Phaeozem than on the Luvic Phaeozem. It was suggested that the use of modified composts led to changes in soil physical properties and micromorphological features and this effect was dependent on the compost application rate. Composts made with the addition of composite synthetic and natural material-derived polymers during composting were found to be a composite mixture that can be successfully used in agriculture.

Effect of calcium silicate on nutrient use of lowland rice and greenhouse gas emission from a paddy soil under alternating wetting and drying

In intensively irrigated rice cultivation,plant-available silicon(Si)is a crucial nutrient for improving rice productivity.As a source of Si,calcium silicate(CaSiO3)was amended to evaluate the effect of silicate fertilizer on rice production,nitrogen(N)use efficiency,and greenhouse gas(GHG)emission under alternating wetting and drying in a pot experiment using a tropical soil from a paddy field of the International Rice Research Institute(IRRI)in the Philippines.Four levels of CaSiO3 amendment,0,112.7,224.5,and 445.8 kg ha^-1,with the recommended N rate were tested.The results showed that although CaSiO3amendment of 112.7 kg ha^-1resulted in higher rice straw,improved N use efficiency,and reduced N2O emission,there was no difference in grain yield among the four levels of CaSiO3 amendment owing to relatively lower harvest index.Moreover,CaSiO3 amendment showed a reverse trend between CH4 and N2O emissions as it reduced N2O emission while led to significantly increased CH4 emission and global warming potential.Thus,CaSiO3 amendment was a possible alternative to improve N use efficiency and increase rice straw biomass,but it needs to be reviewed in line with grain yield production and GHG emission.It is also imperative to test an optimal method of silicate fertilizer amendment in future research in order to compromise a negative impact in tropical soils.