Use of Biochar in Agriculture As Soil Conditioner

Biochar filter: use of biochar in agriculture as soil conditioner

Report for BSAS Commitment 2010

Photo: Jarkko Hovi

Tero Brandstaka1, Juha Helenius1, Jarkko Hovi1, Jukka Kivelä1, Kari Koppelmäki2,

Asko Simojoki3, Helena Soinne4 & Priit Tammeorg1

1University of Helsinki Department of Agricultural Sciences, 2Uusimaa Centre for Economic Development, Transport and the Environment, 3University of Helsinki Department of Food and Environmental Sciences, 4MTT Agrifood Research Finland

University of Helsinki, December 2010

This report is for use of the Baltic Sea Action Summit (BSAS) Helsinki 2010 community http://www.bsas.fi/commitments/all-commitments/biochar-filter-research-on-using-biochar- mixed-soil-in-filtering-impurities-from-water-running-from-agricultural-lands-to-the-baltic- sea

Recommended citation :

Brandstaka, T., J. Helenius, J. Hovi, J. Kivelä, K. Koppelmäki, A. Simojoki, H. Soinne & P. Tammeorg 2010. Biochar filter: use of biochar in agriculture as soil conditioner. Report for BSAS Commitment 2010, 22 pp. December 2010, unpublished.

Abstract

Biochar is material produced via pyrolysis of biomass feedstocks. It is a mixture of char and ash, but it is mainly (70 - 95%) carbon (C). Potential for production of significant amounts of biochar exist, as pyrolysis based technologies are being developed for energy industry and for production of wide variety of chemicals from forest feedstocks.

Potential benefits listed in literature include carbon sequestration by the natural process of photosynthesis, reduction of N2O- ja CH4 -emissions from soils, net production of energy in form of bioenergy, increase in soil fertility and yields of agricultural crops, increase in microbial activity in the soil, improvement of water retention capacity in the soil, improvement of cation exchange capacity in the soil, improvement of durability of soil aggregates and reduction of erosion, reduction in need of fertilization, and reduction of nutrient leaching.

The aims of this study were to test effects of biochar as soil conditioner to soil properties, and to yield and quality of a range of agricultural crops. Direct measurements of impact on nutrient loading were not aimed at. Indirect evidence, through impacts in soil and to yields was seeked for. These include effects on soil aggregate stability, liming effect, water retention, and nutrient use efficiency of agricultural crops. Demonstration in a farmer’s field aimed at getting experience on applicability of biochar in real farming conditions.

The biochar material was carbonized from spruce chips in 500 to 550 oC in an experimental plant in Finland. Its chemical composition, its liming effect, its effect on soil aggregate stability, and its effect on soil moisture were studied. Effects of the biochar on crop growth was demonstrated in a farmer’s field, and field experiments with wheat, turnip rape, faba bean, potato, and sugar beet were conducted in 2010. The application rates varied between 7.5 and 20 t ha-1.

The trace element concentrations in the biochar sample provided by the producer were well within safety limits at the applications rates used. The concentration of water-extractable P in biochar ranged from 5 to 150 mg/kg, revealing high variability even within a batch. There was an indication of higher soil moisture content over the growing season when biochar was applied. The liming effect was lower than by CaCO3. Biochar seemed not to have any effect on the stability of air-dry soil aggregates, but a trend of improved wet aggregate stability by biochar was seen. In farmer’s field, the demonstrated effect of biochar on turnip rape was a 38 % increase in yield in a more fertile field parcel, and even a 69 % yield increase in the least fertile parcel. The replicated field plot experiments were arranged in fertile soils of good soil structure, in which biochar did not give yield increases in any of the crop plant species used in the tests.

Both positive as well as negative impacts were indicated. However, application of biochar to damaged soils of low fertility seems promising. The application rates at the range of 10 to 20 ha-1 seem feasible. However, as we got indication of even yield reductions in fertile soils, we recommend that farmers start experimenting with care, and target the least productive parcels to gain experience.

The variability of the properties of the biochar, even from the same producer and process, was large. Clearly, more research on production of biochar best suited for agricultural use, and further research on biochar as soil conditioner are needed.

Preface

This report is a compilation of results of the first year’s field and laboratory testing of biochar as soil conditioner, initiated as BSAS Helsinki 2010 commitment. It includes results most of which are preliminary. Especially the field experiments require several years to check for natural variability in growing conditions between years. With this reservation in mind, we believe much new information and directions for further research is included, as biochar has not to this extent been studied in Finland before.

We would like to thank Senior Vice President Anja Silvennoinen at UPM and Professor Esa Vakkilainen at LUT, for partnership in our BSAS Commitment. The Chair of JÄRKI project, Mr Ilkka Herlin facilitated the partnership in an important way. We thank Farmer Markus Eerola for enthusiasm and cooperation. Professors Pirjo Mäkelä, Eila Turtola and Markku Yli-Halla contributed in sharing their expertise and in designing the studies. Director of Research Dr. Susanna Muurinen, Director Paavo Kuisma and Senior Researcher Katja Anttila supervised the sugar beet and potato experiments. We are grateful to RAHA project for close cooperation. The participants of the 1st Biochar Seminar in Helsinki in spring 2010 created an enthusiastic and inspiring network which has been important for our work. Especially, cooperation with Preseco Oy, the provider of the biochar used in the experiments, was essential to our research. Honkjoki Oy was an important partner. Contribution from the Ministry of Agriculture and Forestry, which granted us research funding for AgriHiili project (2010-2012) is gratefully acknowledged.

Helsinki 12 December 2010 Authors

List of contents page

Abstract 3 1. Introduction 5 2. Review of current knowledge 6 3. Aims of the study 8 4. Material and methods 8 5. Results 11 6. Discussion 17 7. Conclusion and recommendations 18 References 19 ht t p- l i n k s 20

1. Introduction

Biochar is material produced via pyrolysis of biomass feedstocks. It is a mixture of char and ash, but it is mainly (70 - 95%) carbon (C) (Luostarinen et al. 2010). Charring has a long history, and in many cultures, primitive kilns are still used for making char for fuel. Relatively small volumes of char are being produced in Finland for barbecuing. Potential for production of significant amounts of biochar exist, as pyrolysis based technologies are being developed for energy industry and for production of wide variety of chemicals from forest feedstocks.

In forestry, beneficial effect of ash and char on regrowth of forest after forest fire is well known. Application to agricultural soils has not been practiced in modern farming. However, the bio-char technique, application of char to farmland as soil conditioner is not a new concept. Certain dark earths in the Amazon basin ("terra preta do indio") contain large amounts of biochar (Sombroek et al. 2003, see also Lehman et al. 2006). These soils have been found to be exceptionally fertile, in comparison to soils in the region that do not contain biochar (Lehman et al. 2003).

Internationally, biochar research in recent years has been intensified especially because of the potential biochar provides in carbon sequestration. According to Lehman et al. (2006) biochar as soil conditioner provides an opportunity to annually sequester over 10 % of the carbon emitted due to land use change over the industrial era. This potential is significantly higher than in strategies based on increasing organic carbon in soils, which is estimated to be 0.4 - 1.2 Gt per year (Lal 2004). Production of biofuels by pyrolysis can produce ca. 30 kg biochar per GJ of produced energy. The projected potential for sequestration is estimated to be 5 – 10 Gt C per year, which is equivalent or more than present global emissions from fossil fuel use (5.4 Gt per year) (Lehmann et al. 2006).

Global average is 100 - 200 t carbon per hectare (ha) of agricultural land. In humid and cool regions the soil storage is significantly higher than in arid and hot regions (Lal 2004). In Finnish agricultural soils – excluding organic soils such as peat – typically contain 100 -150 t C per ha.

Cycling of organic carbon from soils to atmosphere is fast in comparison to cycling of biochar, which decomposes only very slowly. The retention times has been estimated to at least hundreds, but more likely thousands of years (Lehmann 2007). Hence, biochar technology provides an opportunity to turn the agri-food sector even to an carbon negative industry. The three main criteria in assessing feasibility of biochar technology are effects on crop productivity and safety, economy, and environment.

Potential benefits include (Lehman et al. 2003, 2006, Lehmann & Joseph 2009, Milne et al. 2007, McHenry 2009):

1) carbon sequestration by the natural process of photosynthesis 2) reduction of N2O- ja CH4 --emissions from soils 3) net production of energy in form of bioenergy 4) increase in soil fertility and yields of agricultural crops 5) increase in microbial activity in the soil 6) improvement of water retention capacity in the soil 7) improvement of cation exchange capacity in the soil 8) improvement of durability of soil aggregates and reduction of erosion 9) reduction in need of fertilization 10) reduction of nutrient leaching

In realizing the potential, pyrolysis technologies such as, for example gasification, need to be developed to meet the multiple and not necessarily parallel needs of production of energy, distillates, and biochar. Perhaps the most critical parameter in the process is temperature. In charring, this usually is 350 – 600 ºC (for more, see Luostarinen et al. 2010). Technology development in projects such as for example in Finland, the TEKES funded (2007-2012) project BioRefine (http 2010) should include biochar considerations.

Research on impact of use of biochar as soil conditioner on nutrient leaching from agricultural soils to waterways has only recently begun. For example, U.S. Department of Agriculture (http 2010) is funding a project on Impact of Biochar on Soil Quality, Crop Yields, Carbon Sequestration, and Water Quality (2008 -2011).

The aim of the research reported here was, as a commitment to the Baltic Sea Action Summit (http BSAS 2010), to screen over one growth season the effects of biochar on crop yields, soil quality, and nutrient leaching potential in Finnish conditions.

2. Review of current knowledge

The discovery of high soil organic carbon on Amazonian Dark Earths has spurred rapidly increasing amounts of research on biochar globally in the last decade or so with many new articles available in 2010 alone. The International Biochar Initiative (IBI 2010) is organizing international conferences on biochar annually and many countries have their own local networks.

In Finland there are about 50 people working with the research and commercialization of biochar including research organizations such as University of Helsinki ,Lappeenranta University of Technology, University of Eastern Finland, MTT AgriFood Research, PETLA Potato Research Institute, SjT Sugar Beet Research Center, and enterprises such as Helsingin Energia, UPM-Kymmene, StoraEnso, Neste Oil etc.

What is already known? It is evident that even large quantities of biochar, ranging from a few tons per ha up to more than 100 t per ha can be added to soils with beneficial impact on soil fertilitity. In some cases biochar carbon has made up almost 40 % of the carbon in soil (Glaser et al. 2000, Skjemstad et al. 2002). In several studies, adding biochar has increased

crop yields even tens of percentages. However, in some other cases, crop growth has also decreased. Rondon et al. (2004) conclude that up to 50 t biochar per ha increases yields (see also Lehmann & Rondon 2006).

Such yield improvements, which are achieved without adding fertilizers, improve nutrient balances at the same rate as the yields improve. In other words, nutrient use efficiency is improved (see: Chan et al. 2008). Lehman et al. (2006) propose that the potentially beneficial application rate for biochar tends to equal the net photosynthesis of the vegetation (which globally reaches ca. 560 Gt annually: Lal 2004). In the Finnish conditions for arable fields this would mean application rates ranging from 5 t to 15 t in carbon equivalents of biochar, in practice 10 to 20 t biochar per ha. The ca 2 million ha of arable land in Finland would, using this range, swallow 20 to 40 million t biochar. Need of renewal of biochar application is an open question, and depends e.g. on decomposition rate.

The aromatic chemical structure of biochar provides much greater resistance to microbial decay than other organic matter and thus has the potential to slow down the carbon cycle in Finland and other countries. Modelled mean residence times of 718-9259 years were obtained by Lehmann et al. (2008) for Northern Australian woodland soils. Similar work for Finland has not been been done.

In soils with low Cation Exchange Capacity (CEC), which are more common in the tropics and sub-tropics than in Finland, biochar seems to have its best potential of boosting agricultural productivity. There also seems to be a liming effect from biochar application in the short-term in many studies. According to research by Cheng et al. (2008), CEC develops slowly over decades or centuries as biochar ages in the soil with latitude determining the speed with which the changes in CEC take place. Major et al. (2010) show how medium-term productivity effects of biochar on soil are noticeable on poor kaolinites and oxisols in Colombia.

Wood biochar is said to have potential to improve water holding capacity, which is currently being investigated. Possible water holding capacity improvements may also contribute to anti-leaching effects. P fertilization effects of biochar are probably primarily due to the release of P salts from the biochar, as well as possibly to decreased P sorption by soil.

Agriculture is responsible for 42% of N2O anthropogenic emissions. Van Zwieten et al. (2010) added 1% and 5% biochar to soil and flooded the soil for 47 days and then measured N2O, the emissions of which were reduced by more than 50% in both biochar addition cases. N2O emissions from biochar application are currently been studied at the University of Eastern Finland in a project led by Docent Sanna Saarnio, and funded by the Ministry of Agriculture and Foresrty for 2010 -2012, and studies are also commencing at the University of Helsinki.

Two recent reviews converge in their assessment of benefits, risks, and open questions in application of biochar to soil. Both emphasize not only the potential, but also the need for further research, including the fact that currently there are not yet markets for biochar (Verheijen et al. 2009, Schakley & Sohi undated).

The need to study biochar over several years in Finland is evident. Since biochar application to soil is irreversible, long-term tests are needed for precaution alone. At the same token, possible long-term benefits will become clearer.

3. Aims of the study

4. Material and methods

- Biochar material

The biochar used in the experiments and tests was produced in an experimental plant of Preseco Oy in Lempäälä, Finland. The raw-material was spruce Picea abies (L.) H. Karst. chips as used also for pulping. The material was partially debarked. The carbonizer was operated at temperature of 500 to 550 oC in a continuous process of 10 to 15 min in duration. The plant was equipped with continuous monitoring of temperature, gas production, and composition of combustion gases for automated adjustment of the temperature and duration for optimal production. The purpose was to produce as much biochar as possible with optimal energy ratio. In this plant, the net heat would be available for heating purposes. Part of the heat is used for drying the biomasses before the carbonizing. The temperature of the produced biochar, when coming out of the process, is over 600 oC, requiring cooling in an air-tight silo. After the cooling, the biochar is moved by an conveyor to a roller mill. The grain size of the product is between fine dust to chips of ca. 5 mm in diameter.

The chemical composition of the biochar, especially of the trace elements in the ash component, were analyzed by Finnish Food Safety Authority EVIRA from a sample provided by the producer Preseco Oy before the experiments commenced.

The concentration of water-extractable P in biochar was measured by equilibrating 0.5 g biochar (dry weight) for 21 hours with 50 ml of deionised water. After the equilibration, the suspensions were filtrated through 0.2 ȝm membrane filter and analysed for PO4-P.

- Analysis of effects in soil

The liming effect of biochar was determined by measuring the pH change of soil suspensions for soil samples with different amounts added of biochar. The liming effect of biochar was compared with those of Ca(OH)2 and CaCO3. A four-day incubation was done with biochar additions corresponding to field additions of 10, 20 and 30 t ha-1.

After the growing season, samples for soil aggregate stability test and for phosphorus analysis were taken from the farmer’s field used for demonstration in Hyvinkää. The effect of biochar on soil aggregate stability was tested by measuring the vulnerability of soil samples to disintegrate and disperse when in contact with water. We used a wet-sieving method where 4 g of soil aggregates (size 2-5 mm, including both field moist and air dried aggregates) are dipped in 100 ml of water for 3 minutes. Water and disintegrated soil material was transferred into a centrifugation tube and left to stand overnight (21 h). Next day the turbidity of

suspension was measured with a turbidity meter. Suspension was centrifuged and supernatant was frozen for later P measurements. The soil pellet was wet-sieved to divide the soil material into two different size-classes (<0.06 and >0.06 mm).

Sampling to follow effects of biochar on soil moisture were taken in the field experiment for wheat in Viikki Experimental farm, from control plots without added biochar and from plots with 15 t ha-1 biochar application. TDR (Time Domain Reflectometry) was used for the measurements taken weekly at depths of 15, 30 and 58 cm.

- Demonstration of yield impacts in farmer's field

In June 2010, a field demonstration was started in the farm of Markus Eerola in Palopuro in Hyvinkää. In this demonstration biochar was applied on the area of 0.15 ha with application level 10 t ha-1. The machine used was a 1.90-meter wide sand application machine. Next to this biochar area a control area with a same size was founded without biochar application. Turnip rape was used as an experimental crop for this demonstration. Field was tilled one week before biochar application with a cultivator tiller. After application of biochar, the uppermost 10-15 cm soil layer of both the biochar area and control area was mixed with the same cultivator tiller, and afterwards tilled with a harrow tiller. The field was sowed one day after tillage and biochar application. The field was divided into two areas inside treatments (control and biochar) based on farmers earlier noticed productivity.

- Field experiment with faba bean, turnip rape and wheat

In May 2010, three four-year completely randomized field experiments with split-plot design were started in the Viikki Experimental Farm of the University of Helsinki (N 60° 13.43’ E 25° 1.67’). The experiments were identical in design, next to each other in the same field parcel. One was for wheat cultivar (cv) Amaretto, another for turnip rape cv Apollo and the third for faba bean cv Kontu. The main plot factor was the biochar application level (0, 7 and 15 t ha-1) and the sub-plot factor was the nitrogen level (100%, 65% and 30% of the crop based appropriate levels, 100% being 40, 130 and 150 kg N ha-1for faba bean, turnip rape and wheat, respectively). There were four replicates in the experiment. Protective plots were used as outermost plots, as well as between separate biochar application rates. The plot size was 2.2 x 10 m and a 2-meter-wide regular agricultural sowing machine was used for sowing.

Biochar was applied 1-2 days before sowing, using a 1.9 m-wide sand application machine, and incorporated to uppermost 5-10 cm soil layer by means of rotary tiller. The sowing of wheat took place on May 19th to the depth of 5 cm. Beans and turnip rape were sown on May 20th to the depth of 3 and 7 cm for turnip rape and beans, respectively.

All crop management practices were conducted by means of conventional agriculture. Beans were sprayed against weeds with herbicide Fenix™ on 26 May. Turnip rape was sprayed against insects with Karate™ on 03 June, against weeds with Galera™ on 16 June, and against white rust disease with Spartak™ on 5 July. Wheat was sprayed against weeds by using Cycocel 750™, Ratio 50 T™ and K-Trio Neste™ on 17 June.

Soil samples for chemical analyses were taken from each experimental plot. The samples for soil chemical properties were frozen for three months and analyzed then for pH and easily soluble Ca, P, K, Mg and S content by a commercial soil testing company Viljavuuspalvelu OY. The results of soil analyses suggested a rather high quality of the soil in the field parcel,

9 and a notable variation within the field. The experimental soil was classified as a Dystric Cambisol (FAO 1998), with average pH of 6.6. All measured properties (pH, Ca, P, K, Mg and S) were at least at a satisfactory level, but in some plots, pH values as high as 7.1 represented an "especially high" level.

All crops were harvested with an experimental plot combine harvester (working width 1.5 m) on 17-20 August and then dried in a box dryer. After drying, the yield was weighed and sorted, and then the cleaned yield was weighed again. A 500-g subsample was taken from each plot's yield, packed in paper bag and stored for crop quality analyses. Next, the 1000 seeds weight (TSW) and the moisture content of dried yield were analyzed and the final yields were calculated to a moisture content of 9% for turnip rape, and to 14% for faba beans and wheat. The data on crop yield and 1000 seed weight (TSW) were analysed by GLM ANOVA to determine the statistical significance of differences between biochar application levels, between different N fertilizer levels and for the interaction of those two (SPSS statistical package 17.2).

- Field experiment with potato

Potato Research Institute PETLA arranged a field experiment in which the effect of biochar on the amount and quality of potato yield was tested for. The experiment was a randomized completed blocks split-plot design with four replicates. The main plot factor was fertilizer type with two levels: either Perunan Y1™ (N 56, P 35, K 133 kg ha-1) or meat bone meal based Viljo™ fertilizer) (56, 35, 7), and the sub-plot factor was biochar application at two levels (5 and 10 t ha-1). The biochar was rotary tilled to soil to depth of 10-15 cm before seedbed preparation. A treatment with no biochar application and with no chemical fertilizer was included as control. The plot size was four 10 m rows gross, 2 inner rows 7 m net.

The potato cultivar was Van Gogh, which was planted 31 May aiming at stem distance 26 cm, the rows being spaced at 80 cm apart. Weeds were controlled by Afalon™ 14 June, and by Titus™ 30 June. Potato blight was controlled six times: 5 July by Epok, 13 June by Revus, 26 June by Curzate+Dithane, 6 and 18 August by Ranman, and 30 August by Shirkan. The experiment was irrigated 14 July and 30 July, both times by 18 mm. Harvesting took place 5 October.

Soil type and fertility was analysed Viljavuuspalvelu OY from soil samples taken before the experiment was established. The soil type was glacial till with a loamy texture (in Finnish, hietamoreeni, Htmr) with high organic matter content (class range 6 - 11.9 % of organic matter). Soil pH was 6.8, which is at the upper end of optimal range for potato. The soil testing results for easily soluble Ca was satisfactory at 1600 mg/l, P was good at 19 mg l-1, K was satisfactory at 140 mg l-1, Mg was good at 270 mg l-1. S was not determined.

Field experiment with sugar beet

SjT Sugar Beet Research Center (Piikkiö) organized a four-year (2010-2013) completely randomized field experiment, in which the effect of biochar application was tested on the amount and quality of sugar beet yield. The design was a completely randomized split-plot desing with fertilizer type as the main plot factor with two levels (mineral compound fertilizer Hiven Y™ (N 23% - P 3% - K 6%) or organic compost at a N application rate of 140 kg ha-1, and biochar application rate as the sub-plot factor at three levels (0, 10 or 20 t ha- 1). The experiment was conducted on a heavy clay soil with organic matter content of 3 %,

10 pH 6.5, P at good to high level, K and Ca at satisfactory levels. The biochar and the compost were applied 11 – 12 May, and rotary tilled to the soil depth of 5-10 cm before seedbed preparation. No additional irrigation was conducted in 2010. SPAD measurements were done twice during the growing season 2010 (12 July and 3 August). The cultivar was Mixer from breeder Hilleshög, and seeds were drilled 18 cm apart 28 May 2010.

5. Results

- Chemical properties of the biochar

The trace element concentrations in the biochar sample provided by the producer were well within safety limits at the applications rates used (Table 1).

The concentration of water-extractable P in biochar used in Viikki experiment 2010 was 150 mg/kg, whereas in the biochar used in Piikkiö it was 5 mg kg-1. In comparison, the water- solubility of P determined for the sample analyzed by Evira was 60 mg kg-1 (Table 1). According to these results, the addition of the biochar used in Viikki at 20 t ha-1 would add water-soluble P 3 kg ha-1 into the soil, whereas that used in Piikkiö would add 0.1 kg ha-1 only.

Table 1. Chemical composition of the biochar used in the studies produced in spring 2010 from spruce chips (see text for details). The moisture of the sample was 22%, and the results are presents as % in dry matter, or as mg/ka in dry matter. The main component, namely carbon (C) is not included: the elements originate from the ash component of the biochar. The tests were carried out by Evira , accredited by Finas (EN ISO/IEC 17025).

Element Content in % dm* Content in mg kg -1 dm Phosphorus (P), total 0.05 Phosphorus (P), water soluble 0.006 Potassium (K) 0.35 Neutralizing capacity (Ca) <1.0 Calcium (CA) 0.61 Copper (Cu) 6.8 Manganese (Mn) 320 Molybdenum (Mo) <0.5 Zink (Zn) 83 Chromium (Cr) 2.4 Vanadium (V) <0.5 Arsenic (As) 0.10 Cadmium (Cd) <0.5 Lead (Pb) 0.71 Nickel (Ni) 3.8 Merqury (Hg) <0.01 *dm = in dry matter

Figure 1. Comparison over time of moisture content of soil in plots without biochar (left, dark green) with soil in plots in which 15 t biochar /ha was applied. The moisture content was measured weekly in wheat plots of lowest fertilization level in Viikki experiment in 2010 by TDR apparatus at depth of 15 cm. Error bars represent standard error of the mean (n=4).

- Impacts in soil

The weekly soil moisture measurements in the Viikki experimental field by TDR indicated a somewhat higher moisture content of the plots with 15 t ha-1 biochar application compared with the plots without any biochar. The tendency was the strongest at the uppermost depth (15 cm) and seemed to be continuous throughout the growing season (Fig. 1).

The liming effect was tested with the biochar batch used in Piikkiö. The pH measured after four days of incubation increased with increased biochar additions but the liming effect was much lower than by CaCO3 (Fig. 2). In a similar manner with the results of water-soluble P, the liming effect probably varies between different biochar materials as well. The liming tests for the biochar batch of Piikkiö is planned to be continued for a longer period, and similar experiment will be carried out for different biochar materials used.

Wet-sieving done for both air-dried and field-moist samples from the farmer’s field in Hyvinkää reflected the division of field into poor and better areas. Biochar seemed not to have any effect on the stability of air-dry soil aggregates (Fig. 3). In a similar manner, the large variation inside the field made it difficult to ascertain the biochar-induced changes in the stability of field-moist soil aggregates (Fig. 4). However, a closer look to the sampling sites and aggregate stability results reveals that the poorer field plot gets worse towards certain direction and when this is taken into account, a trend of improved wet aggregate stability by biochar in the poorer field plot can be seen.

-1 -1 Fig. 2. Liming effect of biochar (0, 10, 20, 30 t ha ) compared to CaCO3 (0, 3, 6 t ha ) expressed as a change of pH during a 4-day incubation. Error bars represent standard deviation of three replicates.

- Demonstration in farmer's field

In the unreplicated field demonstration, the area in which the biochar was applied gave remarkably high yield in comparison to the control area without biochar. On the more fertile side of the parcel, the demonstrated effect of biochar was a 38 % increase in yield, while on the less fertile side, even a 69 % yield increase was seen (Fig. 5).

- Impacts on yield: faba bean, turnip rape and wheat

As for the yield effects by biochar in the growing season 2010, no statistically significant effect of biochar was found for any of the crops, nor was there any significant interaction between biochar application rate and fertilizer level (p<0.05). Although the differences in yields were not statistically significant, some trends seemed visible. In case of beans, on two higher fertilizer levels, biochar seemed to enhance yield, whereas on the lowest fertilizer level, the effect seemed to be negative (Fig. 6).

The results of analyses of variance for the 1000 seed weight (TSW) demonstrated that in case of beans, 7 t ha-1 biochar level resulted in significantly higher TSW than 15 t ha-1char level (p=0.049). No other significant differences were found for beans (p<0.05). For turnip rape, the second-highest N fertilizer level resulted in significantly higher TSW than the highest fertilizer application level (p=0.034). No other significant differences in TSW were found for turnip rape (p<0.05). For wheat, there were no statistically significant dfferences found in 1000 seeds weight (p<0.05).

Fig. 3. Soil material disintegrated from air-dried aggregates (g/g) from Hyvinkää demonstration field. Error bars represent standard deviation of four replicated samples.

Fig. 4. Soil material disintegrated from field-moist aggregates (g/g) from Hyvinkää demonstration field. Error bars represent standard deviation of four replicated samples.

Biochar demonstration 2010, Eerola farm: seed yield of rape

800

700

600 Poor soil 500 Poor soil + biochar a h / 400 g K Better soil 300 Better soil + biochar 200

100

Fig. 5. Rape seed yields in farmer’s field demonstration in Hyvinkää 2010. The two columns on the left are yields from a plot of low fertility and compacted soil, while the two columns on the right are yields from the neighbouring plot of better fertility and structure. The controls (the left column in both pairs) was without biochar. The application rate was 10 t ha-1of biochar.

Fig. 6. The seed yield of beans (14% moisture) in Viikki biochar field experiment 2010. The columns marked with same lowercase letters do not differ significantly (Tukey HSD, p<0,05). Error bars represent standard error (n=4).

50,0 45,0 40,0 35,0 30,0 25,0 Potato yield, t/ha 20,0 Starch yield, t/ha 15,0 10,0 5,0 0,0 Perunan Y1 Viljo + Viljo + Perunan Y1 + Perunan Y1 + biochar 5 t biochar 10 t biochar 5 t biochar 10 t

Fig. 7. Potato yield (t ha-1), and starch yield (t ha-1) of potato cv Van Gogh in Lammi biochar experiment 2010. Conventional mineral potato fertilizer Perunan Y1™ served as control. Biochar was applied either with it or with Viljo™ meat bone meal based fertilizer. Bars: ± standard deviation of the grand mean.

- Impacts on yield: potato

There was no significant effect of biochar on potato yield; there was no indication of yield increase, rather on the contrary (Fig. 7). Nor did biochar have a significant effect on starch content and starch yield (Fig. 7).

- Impacts on yield: sugar beet

The first year results of the sugar beet experiment suggested that in case of mineral fertilizer, there was an increase in sugar beet yields at moderate levels of biochar application (Fig. 8). When compost was used as fertilizer, the sugar beet yields were higher than in case of mineral fertilizer. The highest yields of all treatments (48 t ha-1) were achieved with medium biochar application rate (10 t ha-1). Then again, at the highest biochar application level, there occurred a decrease in beet yield, when compared to medium biochar level.

The same trends were present when calculative sugar yields were observed. However, as the biochar-applied treatments of sugar beet resulted in somewhat higher sugar content, also the trends were more underlined in case of sugar yields rather than for the yields of sugar beet itself. It is also noteworthy, that one replicate block out of four resulted significantly lower yields then other treatments and was thereby removed from the final results. Hence, all the results presented in the current paper are count from replicates I-III.

Fig. 8. The yield of sugar beet and calculated sugar yield of the first growth season of the Piikkiö biochar experiment. Error bars represent standard error of the mean (n=3). Please note that as one replicate differed greatly from other three, the data from it is not included to the graph.

6. Discussion

In terms of trace element composition, including heavy metals, application of the type of biochar used in this study is safe. This said, the laboratory analysis done for two biochar materials suggest that the properties of biochar materials vary a lot. The concentration of water-soluble P and the amount of P that can become soluble during the weathering of biochar should be studied before estimating the environmental impacts of biochar use.

The results on impacts of biochar on such soil properties that directly (e.g. by P sorption) or indirectly (e.g. by enhancing aggregate stabililty) may contribute to the “biochar filter” are still inconclusive at this point of research.

High organic matter content in soil usually increases the aggregate stability. During wet- sieving the decreased slaking of aggregates with high organic matter content results from slower wetting rate. Unexpectedly, the biochar addition appeared not to have this protecting effect on dry aggregates. In the Hyvinkää experiment, the biochar addition seemed to increase the wet aggregate stability in a poorly growing field area, but because of the large heterogeneity of the field no statistically significant differences were detected. To confirm the positive effect of biochar addition on soil aggregate stability and to detect the mechanism of how the biochar affects the soil aggregate structure, a laboratory study with increasing biochar additions and homogenised soil will be done.

An important mechanism by which biochar may reduce nutrient loading is its impact on nutrient use efficiency through increased crop yields. The growing season 2010 was exceptionally dry and hot in Finland, which no doubt affected our results. It is evident, that the great majority of possible biochar effects to plant growth are tightly related to its effects on soil properties. Therefore, the original soil properties are at paramount importance, and this seems to explain the almost spectacular positive effect on yield in the poor and compacted soil of the farmer’s field demonstration, and the neglible yield response to biochar application in the fertile and non-acidic soils of the experimental stations. There is great need for additional research on the effect biochar application has on poorer, more acid and sandy soils.

The results of Viikki field experiment demonstrated that at least on the first application year, biochar levels less than 10 t ha-1 tended to result in the poorest yields. This might partly be attributable to nitrogen immobilisation as significant amounts of high C and low N content material are mixed with soil. The yield increase on higher biochar application levels might be explained by greater water retention capabilities that are achieved due to biochar application.

The yield effects in the sugar beet experiment point out a noteworthy difference of yield responses for different biochar application depending on the fertilizer type. In case of mineral fertilizer, sugar beet yields increased steadily together with biochar levels. However, this was not the case for the compost-fertilized treatments, which achieved their maximum yield at the medium biochar application level (10 t ha-1) and decreased, when additional biochar was applied. This effect could be partly attributable to nitrogen deficiency that might have occured as a result of too large amount of carbon in soils (compost + biochar) in relation to available nitrogen. Therefore, possible competition for available nitrogen between soil micro- organisms and sugar beet plants might have resulted in lower beet yields. In case of mineral fertilizer, there was less carbon added to soil and so the C/N ratio would stay narrower, allowing plants to yield higher.

7. Conclusions and recommendations

As both positive as well as negative impacts were indicated in this one year exercise, clearly, more, and more specific, further research is needed. Biochar is not a silver bullet to improve nutrient economy in farming, or to increase crop yields. However, application of biochar to damaged soils of low fertility seems promising.

The application rates at the range of 10 to 20 ha-1 seem feasible. However, as we got indication of even yield reductions in fertile soils, we recommend that farmers start experimenting with care, and target the least productive parcels to gain experience.

The variability of the properties of the biochar, even from the same producer and process, was large. Clearly, more research on production of biochar best suited for agricultural use is needed.

This also emphasizes the importance of characterizing the properties of biochar used for the experiments. Futher investments to research on biochar as soil conditioner are warranted, obviously due to carbon sink function, but also, because of potential for increased nutrient use efficiency in farming.

References

Cheng, C., Lehmann, J., Engelhard, M. 2008. Natural oxidation of black carbon in soils: Changes in molecular form and surface charge along a climosequence. Geochimica et Cosmochimica Acta 72:1598--1610.

FAO 1998. World Reference Base for Soil Resources. Rome: Food and Agriculture Organization of the United Nations.

Lal, R. 2004. Soil carbon sequestration impacts on global climate change and food security. Science 304: 1623-1627.

Lehmann, J. 2007. A handful of carbon. Nature 447: 143-144.

Lehmann, J., J. Gaunt & M. Rondon 2006. Bio-char sequestration in terrestrial Ecosystems – a review. Mitigation and Adaptation Strategies for Global Change 11: 403--427

Lehmann, J. & S. Joseph 2009. Biochar for environmental management: science and technology. Earthscan, London. 416 p.

Lehmann, J., D.C. Kern, L.A. German, J. McCann, G.C. Martins & A. Moreira 2003. Soil Fertility and Production Potential. In: J. Lehmann, D.C. Kern, B. Glaser and W.I. Woods (eds.), Amazonian Dark Earths: Origin, Properties, Management, pp. 105--124. Dordrecht, Kluwer Academic Publishers.

Lehmann, J. & M. Rondon 2006. Bio-char soil management on highly-weathered soils in the humid tropics. In: N. Uphoff, A.S. Ball, E. Fernandes, H. Herren, O. Husson, M. Laing, C. Palm, J. Pretty & P. Sanchez (eds.), Biological Approaches to Sustainable Soil Systems, pp. 517-530. Boca Raton, CRC Press.

Lehmann, J., Skjemstad, J., Sohi, S., Carter, J., Barson, M., Falloon, P., Coleman, K., Woodbury, P., Krull, E. 2008. Australian climate-carbon cycle feedback reduced by soil black carbon. Nature Geoscience 1:832-835.

Luostarinen, K., E. Vakkilainen & G. Bergamov 2010. Biochar filter - carbon containing ashes for agricultural purposes. Lappeenranta University of Technology, Faculty of Technology. LUT Energy, Research report 9,

Major, J., Rondon, M., Molina, D., Riha, S., Lehmann, J. 2010. Maize yield and nutrition during 4 years after biochar application to a Colombian savanna oxisol. Plant and Soil 333:117-128.

McHenry, M.P. 2009. Agricultural bio-char production, renewable energy generation and farm carbon sequestration in Western Australia: certainty, uncertainty and risk. Agriculture, Ecosystems and Environment 129: 1-7.

Milne, E., D.S. Powlson, C.E. Cerri 2007. Soil carbon stocks at regional scales. Agric. Ecosyst. Environ. 122: 1--2. (preface)

Rondon, M., J. Lehmann, J. Ramirez, & M.P. Hurtado 2004. Biologial nitrogen fixation by common beans (Phaseoulus vulgaris) increases with charcoal additions to soils. In: Integrated Soil Fertility Management in the Tropics, pp. 58--60. Annual Report of the TSBF Institute, CIAT, Cali, Colombia.

Shackley, S. & S. Sohi (eds) undated. An assessment of the benefits and issues associated with the application of biochar to soil. A report commissioned by the United Kingdom Department for Environment, Food and Rural Affairs, and Department of Energy and Climate Change. 132 pp.

Skjemstad, J.O., D.C. Reicosky, A.R. Wilts, & J.A. McGowan 2002. Charcoal carbon in U.S. agricultural soils. Soil Science Society of America Journal 66: 1249--1255.

Sombroek, W., M.L. Ruivo, P.M. Fearnside, B. Glaser & J. Lehmann 2003. Amazonian Dark Earths as carbon stores and sinks. In: J. Lehmann, D.C. Kern, B. Glaser & W.I. Woods (eds.), Amazonian Dark Earths: Origin, Properties, Management, pp. 125--139. Dordrecht, Kluwer Academic Publishers.

Van Zwieten, L., Kimber, S., Morris, S., Downie, A., Berger, E., Rust, J., Scheer, C. 2010. Influence of biochars on flux of N2O and CO2 from ferrosol. Australian Journal of Soil Research 48: 555-568.

Verheijen, F., S. Jeffery, A.C. Bastos, M. van der Velde, I. Diafas 2009. Biochar application to soils. A critical scientific review of effects on soil properties, processes and functions. JRC Scientific and Technical Reports. EUR 24099 EN, Office for the Official Publications of the Europan Communities, Luxembourg, 149 pp.

http:// -links

BioRefine (2010), last visited 18.12.2010 http://www.tekes.fi/programmes/biorefine

BSAS (2010), last visited 18.12.2010 http://www.bsas.fi/commitments/all-commitments/biochar-filter-research-on-using-biochar-mixed- soil-in-filtering-impurities-from-water-running-from-agricultural-lands-to-the-baltic-sea

IBI (2010), last visited 18.12.2010 http://www.biochar-international.org/

U.S. Department of Agriculture (2010), last visited 18.12.2010 http://www.ars.usda.gov/research/projects/projects.htm?accn_no=414740

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