Softwood biochar as a soil amendment material for boreal agriculture

Biochar is a porous carbonaceous solid material produced by pyrolysis. Application of biochar is considered as an efficient way of carbon (C) sequestration since the C in biochar is relatively resistant to microbial degradation. Furthermore, previous research in (sub-) tropical conditions suggests that it may enhance soil fertility and the yields of agricultural crops. To target the lack of knowledge about the effects of biochar in the boreal zone, softwood biochar was added to two boreal soils (a fertile Stagnosol and a nutrient deficient Umbrisol) in laboratory and field experiments in southern Finland in 2010 2012. The study focused on the effects of biochar on 1) the mineralisation of nitrogen (N) of organic fertilisers, 2) the physicochemical properties of soil, 3) earthworm abundance and behaviour, and 4) the yield formation of wheat, turnip rape and faba bean. Biochar application to soils caused an initial reduction in N availability, probably by N immobilisation due to increased microbial biomass. The effect was greater when the biochar application was combined with an organic fertiliser with a high C:N ratio than when one with a low C:N ratio was used. In the field experiments, however, the N immobilisation was moderate, as the N uptake of crops was not affected. Furthermore, signs of turnover of microbial biomass in the second year were seen in the Umbrisol field. Biochar application increased the contents of C and exchangeable potassium (K) in the soil, but had no significant effects on other soil chemical properties within the first two to three years of the experiments. Biochar effects on soil physical properties varied. In the Stagnosol with a sandy clay loam texture, the application slightly increased topsoil moisture content, but did not affect soil water retention or porosity. In the Umbrisol with a loamy sand texture, biochar increased the plant-available water content of the topsoil in the first year and soil porosity in the second year but did not affect the moisture content of the soil. In the laboratory, biochar did not affect the habitat choice of earthworms when the test lasted for 2 days, but after 2 weeks, biochar-treated soil was avoided. The avoidance effect was associated with a slight decline in soil water potential. This avoidance effect was not observed under field conditions, where there was even an indication of increased abundance and biomass of earthworms in biochar-amended soil. The effects of biochar application on the plant growth dynamics and N uptake of turnip rape and wheat were not significant, but the enhanced accumulation of biomass and N uptake of faba bean during the initial N immobilisation phase may be related to possibly enhanced biological N fixation. In dry years, biochar addition affected the yield formation of crops, as it was associated with decreased plant density and increased number of reproductive units (pods, siliques or ears) per plant. The latter was attributed to two additive mechanisms, the compensation for decreased plant density and relieved moderate water deficit. Biochar did not however affect the crop yield significantly, irrespective of the fertiliser treatments or the soil types studied. It can be concluded that the application of biochar in combination with inorganic fertilisers or with meat bone meal to boreal soils with near neutral pH and relatively high original SOM content may reduce deficits in both K and water, but should not be expected to significantly affect yields of faba bean, turnip rape and wheat during the first few years. As added biochar had no negative effects on crop yields or earthworms, it can be suggested that softwood biochar application is an agriculturally safe way of sequestering C. Considering the longevity of biochar in soils, future studies are needed for monitoring the long-term effects of biochar under field conditions.Biohiiltä muodostuu, kun biomassaa kuumennetaan hapettomissa oloissa. Se on kiinteää ja huokoista ainetta, jossa on paljon aromaattisia rakenteita, joita mikrobit eivät pysty hajottamaan. Tästä syystä on esitetty, että biohiilen sekoittaminen maahan olisi tehokas keino poistaa ilmakehästä ilmastonmuutosta aiheuttavaa hiilidioksidia. Subtrooppisessa ilmastossa maahan lisätty biohiili on myös parantanut maan viljavuutta ja nostanut viljelykasvien satoja. Yksi varhaisimmista biohiilen käyttöpaikoista lienee Amazonasin alue, jossa muinainen intiaanikulttuuri jo lähes 3000 vuotta sitten lisäsi maahan puuhiiltä, mikä muutti alueen luontaisesti köyhän maaperän viljavaksi. Mahdollisuus lisätä maahan varastoituneen hiilen määrää ja maaperän viljavuutta biohiilen avulla ovat tärkeimmät syyt viimeisen kymmenen vuoden aikana voimakkaasti lisääntyneeseen biohiili tutkimukseen. Biohiilen vaikutuksista pohjoisten ilmasto-olojen viljelymaissa ei juuri ole ollut saatavilla tutkimustietoa. Tästä syystä Helsingin yliopistossa tehtiin vuosina 2010 2012 kaksi laboratorio- ja kenttäkoetta, joissa tutkittiin biohiilen vaikutuksia eloperäisten lannoitteiden typen mineralisaatioon, maaperän fysikaalisiin ominaisuuksiin, ravinnetilaan ja lierojen käyttäytymiseen sekä viljelykasvien sadon muodostumiseen. Laboratoriokokeen perusteella biohiili vähentää eloperäisistä lannoitteista vapautuvan typen määrää ensimmäisten kuukausien aikana. Vaikutus oli suurempi korkean hiili:typpi suhteen lannoitteilla (kuten kompostoidulla karjanlannalla) kuin matalan hiili:typpi suhteen lannoitteilla (kuten lihaluujauholla). Syynä ilmiöön on luultavasti typen immobilisoituminen mikrobeihin. Mikrobeihin sitoutunut typpi saattaa kuitenkin seuraavien kasvukausien aikana vapautua kasvien käyttöön. Vaikka typen immobilisoitumisesta saatiin näyttöä myös kenttäkokeessa, vaikutukset olivat pienemmät kuin laboratorio-oloissa. Vähiten viljavassa peltomaassa biohiili lisäsi mineraalitypen määrää maassa toisen kasvukauden jälkeen, mikä tukee laboratoriokokeesta tehtyä johtopäätöstä mikrobiston runsastumisesta. Kenttäkokeissa biohiili nosti kyntökerroksen hiilipitoisuutta sekä liukoisen kaliumin määrää, mutta ei vaikuttanut merkitsevästi muihin maan kemiallisiin ominaisuuksiin. Biohiili lisäsi myös viljavan savisen hietamaan kyntökerroksen kosteutta sekä pintamaan vedenpidätyskykyä ensimmäisenä vuotena viljavuudeltaan heikommassa hietamaassa. Kaksi vuorokautta kestäneessä laboratoriossa toteutetussa käyttäytymiskokeessa biohiili ei vaikuttanut lieroihin merkitsevästi, mutta kaksi viikkoa kestäneessä kokeessa lierot välttivät maata, johon oli lisätty biohiiltä. Välttäminen johtui luultavasti biohiilen aiheuttamasta maan matriisipotentiaalin laskusta. Kenttäkokeessa ei välttämistä kuitenkaan havaittu. Päinvastoin, biohiilikäsittelyissä esiintyi jopa hieman enemmän lieroja kuin kontrollikäsittelyissä. Tämä saattaa viitata siihen, että biohiilen lisäämä mikrobibiomassa on tärkeää myös lieroille, mahdollisesti ravinnelähteenä. Kenttäkokeessa biohiili vaikutti poutavuosina viljelykasvien sadonmuodostukseen kasvustotiheyden harventumisen ja kasviyksilön palkojen, litujen tai tähkien lukumäärän lisääntymisen kautta. Kasviyksilön siementen lukumäärän runsastuminen saattaa selittyä satokomponenttien kompensoitumisella ja/tai biohiilen aiheuttamalla maan kosteuden nousulla sekä kasvien kokeman kuivuusstressin alenemisena. Biohiilen myönteiset vaikutukset eivät kuitenkaan johtaneet sadon runsastumiseen. Tämä tutkimus toteutettiin tyypillisillä suomalaisilla kivennäismailla, joiden pH on lähellä neutraalia ja jotka sisältävät paljon orgaanista hiiltä (yli 3 %). Tulokset tukevat käsitystä, jonka mukaan biohiilen lisäys maahan ei Suomen oloissa välttämättä lisää merkitsevästi satoja ensimmäisenä kolmena vuotena. Se voi kuitenkin lisätä maahan kaliumia ja hiiltä sekä parantaa maaperän rakennetta ja myös lisätä maaperäeliöstön toimintaa. Maahan lisätyn biohiilen käyttö hiilinieluna on tulosten perusteella turvallinen menetelmä maaperän fysikaalisten, kemiallisten ja biologisten ominaisuuksien kannalta. Koska biohiili säilyy maassa jopa tuhansia vuosia eivätkä kaikki sen vaikutukset ilmene välittömästi, on tarpeen tutkia biohiilen vaikutuksia pitkäkestoisissa kenttäkokeissa

Meat and bone meal as a nitrogen and phosphorus fertilizer for ryegrass

Meat and bone meal (MBM) is a valuable co-product of the rendering industry. Its feed and fertilizer uses were restricted in the EU in 2002 as a result of the occurrence of BSE crisis. Consequently, MBM was land filled, incinerated or used as an alternative fuel in cement production. The re-allowance of the fertilizer use of MBM in the EU since spring 2006 together with the rising prices of industrial nitrogen and phosphorus fertilizers have resulted in amplified research and use of MBM as a fertilizer. Additionally, growing consciousness of both finiteness of resources and deteriorating environmental effects of the artificial fertilizer use have contributed to growing popularity of nutrient recycling. The fertilizer effect and the nutrient uptake efficiencies of the Finnish MBM (N-P-K-Ca 8–6-0.5-15%) compared to mineral counterparts were tested for in present study. Additionally, the fertilizer effect of MBM in mixture with two potassium fertilizers was tested for. A greenhouse experiment with ryegrass (Lolium multiflorum) fertilized with five fertilizers (MBM, mineral fertilizers Y4PK and NK, two mixtures of MBM and potassium fertilizers) was conducted from 2007 to 2008 in Department of Agricultural Sciences greenhouses in University of Helsinki, Finland. Each of the fertilizers was applied on three nitrogen levels (80, 160 and 240 kg N ha-1). Four additional reference treatments (0 kg N ha-1 fertilizer, PK I, PK II and PK III) were included. Six cuts of ryegrass were cut and the yields were recorded. Post-harvest plant and soil analyses were conducted. MBM was shown to be a highly effective N and P fertilizer with fertilizer effect similar or even longer lasting than artificial Y4PK fertilizer. Additionally, unlike highest application levels of mineral fertilizer Y4PK and NK, meat and bone meal treatments did not lower the pH level of the soil. Therefore, it can be concluded that the relatively high Ca content of MBM is useful in preventing further costs for liming the soil. The nutrient uptake efficiencies of MBM were generally somewhat lower than for mineral counterparts. That could be partly attributable to possible immobilization of MBM-N to soil and partly to lower readily plant-available P content of MBM than mineral fertilizers. However, as significant amount of MBM-P is still available for following years, it is justified to use MBM only once in a crop rotation. That makes MBM an especially effective complementary N and P fertilizer for organic farming, where most of the nitrogen need in crop rotation is covered with legumes and manure. The fertilizing potential for mixture of MBM and K fertilizers was shown to be rather high. However, the lack of affordable potassium sources suitable for organic farming is a recognized challenge. Additional research is needed for convalescing MBM as NPK fertilizer

Recycling lake sediment to agriculture : Effects on plant growth, nutrient availability, and leaching

Sediment removal from eutrophicated shallow lakes may not only be an effective method for lake restoration but also provides the potential for recycling nutrients from sediments to crop production. However, finding a suitable strategy for sustainably reusing the sediment remains a challenge. Therefore, current study focused on the best practices in applying the sediment from a shallow eutrophicated lake to the soil in terms of grass yield, nutrient uptake, and nutrient leaching. During a nine-month lysimeter experiment, 100-cm high columns were filled with six combinations of soil, sediment, and biochar, with or without meat bone meal organic fertilizer. Aboveground biomass, root mass distribution in soil, nutrient concentration, phosphorus (P) uptake of perennial ryegrass (Lolium perenne L.) along with easily soluble nutrients in the growing medium, and leached mineral nitrogen (N) and P levels were measured. Plant growth conditions were improved by sediment additions, as the yield and P uptake of ryegrass nearly doubled in treatments containing sediment compared to the control soil. While the sediment was richer in macro and micronutrients (e.g. P and N) compared to the soil, the leached N and P levels from both treatments were almost equivalent (N < 830 mg m−2 and P < 3 mg m−2). In addition, applying a 2-cm layer of biochar between the sediment and soil reduced P and N leaching by 50%. According to the results, applying a 75-cm thick layer of sediments on agricultural sandy loam soils surrounding the lake seems a promising practice for improving plant yield and soil nutrient status without increasing of P and N leaching from soil.Peer reviewe

Internal phosphorus loading in a small shallow Lake: Response after sediment removal

Mankind is taking advantage of numerous services by small shallow lakes such as drinking water supply, irrigation, and recreational function; however, many of these lakes suffer from eutrophication. Given the key role of phosphorus (P) in eutrophication process, one of the effective restoration methods especially for small shallow lakes is removal of sediments enriched with nutrients. In our study, we used interannual, seasonal, and spatial data to examine the changes in sediment P mobility after removal of sediments in 2016 from a 1-ha highly eutrophic lake. We measured the sediment redox potential, analyzed soluble reactive P (SRP) in the pore water and P fractional composition of the surface sediments, and calculated the P diffusive flux in three locations in two continuous years (2017 and 2018) after the excavation. Similar measurements were done before sediment removal at central site of the lake in 2015. Removing nutrient-rich sediment also removed 6400 kg of P, and thus the potential for release of P from sediments decreased on a long-term scale. However, a large pool of releasable P was rebuilt soon after the sediment removal due to high external P loading, resulting in extensive anoxia of sediment surface and associated internal P loading as high as 1450 mg m−2 summer−1. Moreover, the Fe-P and labile P fractions were the most important sources of P release, as evidenced by their considerable seasonal and interannual changes after the sediment removal. The sediment total Fe negatively correlated with sediment P diffusive flux, pore water SRP, and near-bottom water total P and SRP concentrations which indicated a strong linkage between sediment P dynamics and Fe after the restoration. Sediment removal could be a beneficial restoration approach, but the effects on lake water quality remain only short-term unless there is an adequate control on external loading to the lake.Peer reviewe

Improving Group Work Practices in Teaching Life Sciences : Trialogical Learning

Trialogical learning, a collaborative and iterative knowledge creation process using real-life artefacts or problems, familiarizes students with working life environments and aims to teach skills required in the professional world. We target one of the major limitation factors for optimal trialogical learning in university settings, inefficient group work. We propose a course design combining effective group working practices with trialogical learning principles in life sciences. We assess the usability of our design in (a) a case study on crop science education and (b) a questionnaire for university teachers in life science fields. Our approach was considered useful and supportive of the learning process by all the participants in the case study: the students, the stakeholders and the facilitator. Correspondingly, a group of university teachers expressed that the trialogical approach and the involvement of stakeholders could promote efficient learning. In our case in life sciences, we identified the key issues in facilitating effective group work to be the design of meaningful tasks and the allowance of sufficient time to take action based on formative feedback. Even though trialogical courses can be time consuming, the experience of applying knowledge in real-life cases justifies using the approach, particularly for students just about to enter their professional careers.Peer reviewe

Drought stress and Acacia seyal biochar effects on sorghum gas exchange and yield: A greenhouse experiment

Drought is the controlling abiotic stress factor affecting crop production in dryland environments and exposes millions of people to food insecurity in Africa and Asia. Although sorghum is drought tolerant, it is not sufficiently known if biochar can reduce drought-related losses in yields in clay soils for this particular crop. The stomatal morphology and gas exchange responses were investigated of a sorghum cultivar, ‘Wad Ahmed’ (widely grown throughout Sudan and South Sudan), to drought stress and Acacia seyal biochar application in a greenhouse pot experiment. The experiment was set up in a split-plot, randomized block design with two experimental factors: drought stress (60%, 40%, 20% of field capacity) and biochar (no biochar and 10 Mg/ha). The potting soil was clay textured with 5% carbon content. There were eight replicate pots of each treatment which were arranged randomly in six blocks giving a total of 48 pots. The experiment lasted 153 d from sowing, with 127 d of drought treatment. The results showed that while drought stress had a significant (p < 0.05) effect on gas exchange, water use efficiency, biomass and grain yield, biochar had no significant effect, and neither drought stress nor biochar had a significant effect on stomatal size and density. It may be that high doses of biochar are required to benefit crops grown under drought stress, particularly when the soils have initially high soil organic carbon content, with more time needed for any effect to become evident.Peer reviewe

Effects of two wood-based biochars on the fate of added fertilizer nitrogen—a 15N tracing study

A 15N tracing pot experiment was conducted using two types of wood-based biochars: a regular biochar and a Kon-Tiki-produced nutrient-enriched biochar, at two application rates (1% and 5% (w/w)), in addition to a fertilizer only and a control treatment. Ryegrass was sown in pots, all of which except controls received N-15-labelled fertilizer as either (NH4NO3)-N-15 or (NH4NO3)-N-15. We quantified the effect of biochar application on soil N2O emissions, as well as the fate of fertilizer-derived ammonium (NH4+) and nitrate (NO3-) in terms of their leaching from the soil, uptake into plant biomass, and recovery in the soil. We found that application of biochars reduced soil mineral N leaching and N2O emissions. Similarly, the higher biochar application rate of 5% significantly increased aboveground ryegrass biomass yield. However, no differences in N2O emissions and ryegrass biomass yields were observed between regular and nutrient-enriched biochar treatments, although mineral N leaching tended to be lower in the nutrient-enriched biochar treatment than in the regular biochar treatment. The N-15 analysis revealed that biochar application increased the plant uptake of added nitrate, but reduced the plant uptake of added ammonium compared to the fertilizer only treatment. Thus, the uptake of total N derived from added NH4NO3 fertilizer was not affected by the biochar addition, and cannot explain the increase in plant biomass in biochar treatments. Instead, the increased plant biomass at the higher biochar application rate was attributed to the enhanced uptake of N derived from soil. This suggests that the interactions between biochar and native soil organic N may be important determinants of the availability of soil N to plant growth.Peer reviewe

Factors behind the variability of phosphorus accumulation in Finnish lakes

Phosphorus retention (TPacc) is one of the major water quality regulators in lakes. The current study aimed at ascertaining the specific lake characteristics regulating TPacc. Moreover, we were interested whether NAO (North Atlantic Oscillation), a proxy of climatic forcing, can explain variability in TPacc, additionally to that ascribed to lake characteristics. Sediment cores were obtained from 21 Finnish lakes, subject to radiometric dating and measurements of TP concentrations. Principal components (PCs) were generated using lake characteristics that are usually included into the modelling of TPacc (e.g. lake area, lake depth, catchment area, P inflow) but also the parameters that the classical models usually missed (e.g. anoxic factor). We used significant principal components (PCs), specific combinations of lake characteristics and monthly NAO values as predictors of TPacc. Lake characteristics explained the bulk of TPacc variability. The most influential factors (positive drivers) behind TPacc included PC1 (representing mainly deep lakes), PC2 (small lakes with high levels of anoxia and water column stability), PC3 (productive lakes with large catchment area and short water residence time), PC4 (lakes with high water column stability, low anoxic factor and relatively high sediment focusing) and PC5 (lakes with high levels of P inflow, anoxia and long water residence time). Additionally, we found a potential negative effect of NAO in October on the annual TPacc. This NAO was significantly positively related to temperatures in surface and near-bottom water layer (also their difference) in autumn, suggesting the possible implications for the internal P dynamics. Increased mineralization of organic matter is the most likely explanation for the reduced TPacc associated with NAO-driven water temperature increase. The analysis presented here contributes to the knowledge of the factors controlling P retention. Moreover, this spatially and temporally comprehensive sediment data can potentially be a valuable source for modelling climate change implications.Peer reviewe

Role of Biochar and Fungi on PAH Sorption to Soil Rich in Organic Matter

The use of biochar (BC) has been suggested for remediation of contaminated soils. This study aims to investigate the role of microorganisms in sorption of PAH to BC-amended soils. Fungi, especially the wood and litter-degrading fungi, have shown the ability for humification and to degrade recalcitrant molecules, and are thus suitable model organisms. Haplic Arenosol with high organic matter content was chosen to highlight the importance of soil organic matter (SOM) in PAH sorption, possibly to form non-extractable residue. Basidiomycetous fungi Agrocybe praecox and Phanerochaete velutina grown on pine bark were inoculated in organic matter (OM)-rich Haplic Arenosol and OM-poor sandy loam with either BC or chemically activated BC (ABC) and 14C-labelled pyrene for 60 days. Fungi did not mineralize pyrene, but increased sorption up to 47–56% in BC-amended Haplic Arenosol in comparison with controls (13–25%) without a fungus irrespective of the presence of an adsorbent. In OM-poor sandy loam, only 9–12% of pyrene was sorbed to amended soil in the presence of fungus and adsorbent. The results suggest that BC and fungal amendment increased sorption of pyrene, especially to Haplic Arenosol more than by either BC or fungi alone.Peer reviewe