Open . 2018; 3: 284–290

Research Article

Christoph Steiner*, Keith Harris, Julia Gaskin, KC. Das The nitrogen contained in carbonized litter is not plant available https://doi.org/10.1515/opag-2018-0030 received February 7, 2018; accepted June 26, 2018 1 Introduction

Abstract: Pyrolysis of , reduces its volume, mass, There is growing concern about the large amounts of odour, and potential pathogens, while concentrating manure being generated by large animal feeding operations nutrients in the resulting biochar. However, the plant and the potential hazard for water eutrophication and air availability of nutrients in particular of nitrogen remains quality. In many cases there is insufficient land available largely unknown. Therefore, we investigated the nutrient for spreading the manure at agronomic rates and the availability of carbonized poultry litter. A nutrient poor increasing scale of animal feeding operations which has soil was either fertilized with poultry litter or poultry litter caused accumulation of excess nutrients. The poultry carbonized at 500°C at the rates of 1.5, 3 and 6 t/ha. These industry in the US produces 576,436 t of nitrogen (N) and organic amendments were compared with corresponding 276,932 t of phosphorus (P) representing an excess of rates of mineral (NH4NO3, KCl, CaHPO4, MgSO4) in 483,646 and 252,493 t respectively (Gollehon et al. 2001). a pot experiment. After four successive harvests of ryegrass Thermochemical conversion (pyrolysis) might be (Lolium sp.) in a greenhouse we analyzed plant nutrient one option to process poultry litter for renewable energy uptake and nutrient concentrations in the soil. While all (synthesis gas and hydrocarbon fuels) and biochar treatments showed a linear increase in plant growth and (Cantrell et al. 2007; Schnitzer et al. 2007; Tagoe et al. nitrogen uptake, the plants fertilized with carbonized 2008). Biochar is the residue and consists of minerals and poultry litter did not show such a response. The carbonized fixed carbon (C). In comparison to common biological poultry litter treatment produced more biomass than the treatments like composting, pyrolysis of poultry litter unfertilized control, but the tissue concentration of nitrogen is faster; requires less space and; destroys potential was below that of the control. Mehlich 1 extractable nutrients pathogens and most pharmaceutically active compounds in the soil showed that there is more available phosphorus, and reduces gaseous emissions (Cantrell et al. 2007). potassium, calcium and magnesium in the soil fertilized with During the pyrolysis process important plant nutrients the carbonized poultry manure, but these available nutrients (P, K+, Ca2+, and Mg2+) are concentrated in the biochar were not utilized due to the nitrogen limitation to plant (Gaskin et al. 2008). This might facilitate a more efficient growth. The results clearly show that nitrogen contained in nutrient recovery by reducing the costs associated with carbonized poultry litter is not available for plants. land application and transportation. But depending on pyrolysis temperature, some nutrients susceptible Keywords: black carbon, carbon sequestration, fertilization, to volatilization such as N are partially lost during the nutrient availability, pyrolysis process (Gaskin et al. 2008). Research on biochar as a soil improver have shown beneficial effects on soil fertility apart from its nutrient *Corresponding author: Christoph Steiner, The University of Georgia, Department of Biological and , content (Glaser et al. 2002; Lehmann et al. 2003; Steiner et Driftmier Engineering Center, Athens, 30602 GA, USA, E-mail: al. 2007). Biochar has also received attention as a potential

[email protected] sink for atmospheric CO2 (Lehmann et al. 2006; Steiner KC. Das, The University of Georgia, Department of Biological and 2007; Gaunt and Lehmann 2008), due to its recalcitrance Agricultural Engineering, Driftmier Engineering Center, Athens, against decomposition (Kuzyakov et al. 2009; Smith et al. 30602 GA, USA 2010). Keith Harris, US EPA, Athens, GA, 30605 Julia Gaskin, Crop and Soil Sciences Dept, College of Agricultural However, this recalcitrance seems to have implications and Environmental Sciences, University of Georgia, Athens, GA to nutrient availability. Knicker et al. (2005) have shown 30602 that fire and carbonization can increase the N content

Open Access. © 2018 Christoph Steiner et al., published by De Gruyter. This work is licensed under the Creative Commons Attribution- NonCommercial-NoDerivs 4.0 License. The nitrogen contained in carbonized poultry litter is not plant available 285 of soil organic carbon, but the alterations in chemical (shown in Table 1). structure have long-term consequences for N availability Poultry litter was obtained from a house (Knicker and Skjemstad 2000). Yet Tagoe et al. (2008) and carbonized in a batch reactor at a constant 500oC found no difference in N uptake by crops if fertilized with carbonization temperature for 0.5 h using N2 carrier gas. carbonized or un-carbonized manure. Soybean Both un-carbonized (PL) and carbonized poultry litter seed yield was higher on soils fertilized with carbonized (PLc) were analyzed for total C and nutrient contents as chicken litter (based on equal N applications) due to the above (Table 2). higher P content of carbonized chicken manure. The extent to which the retained or concentrated elements in biochar are available for plants is unclear. A 2.2 Treatment preparation better understanding of biochar’s properties and how it affects soil fertility is needed before it can be more widely Pots with a volume of 4 L were filled with 3,600 g (3,044 g accepted for use in agriculture. Our objectives were to dry weight) soil. First 1,200 g of soil was placed on the compare soil fertilization efficiency of carbonized chicken bottom of the pot and the remaining 2,400 g was mixed litter with both un-carbonized chicken litter and mineral with the fertilizers (either PL, PLc or mineral fertilizers (s. . We hypothesize that a large proportion of P, K+, below). The organic soil enrichments (PL and PLc) were Mg2+, and Ca2+ present in carbonized chicken litter are applied at the rates of 1.5, 3.0, and 6.0 t/ha. By coincidence readily available to plants whereas N uptake is reduced in the N content of PL (35.2 g/kg) was very close to that of PLc comparison to un-carbonized chicken litter and mineral N (35.0 g/kg). The concentrations of other elements such as fertilization. P, K +, Ca2+, and Mg2+ were approximately twice as high in PLc than PL (Table 2). An increasing concentration of these elements and 2 Materials and methods a loss of N by volatilization are common for this type of feedstock (Gaskin et al. 2008). The three application 2.1 Soil and soil amendments rates and the nutrient concentrations should allow a direct comparison of available nutrients. For the Unfertilized sandy topsoil was collected at a near mineral fertilized controls, we mixed ammonium nitrate

Athens (GA, USA). The soil was screened through 4 mm (NH4NO3), potassium chloride (KCl), calcium phosphate mesh into three separate bins. A subsample from each (CaHPO4), and magnesium sulfate (MgSO4) in a ratio to bin was analyzed for cation exchange capacity (CEC), match the nutrient contents of each litter treated soil (PL pH, total and available nutrient (Mehlich I) and C content and PLc) and designated MF and MFc, respectively. One

Table 1: Soil characteristics: pH, total and available nutrient content (means, n=3) pH Elements C N S P K Ca Mg Al Fe Na Zn B Mn

g/kg mg/kg

CaCl2 4.75 Total 18.9 1.6 0.19 410.6 2318 1015 1623 36280 37227 60.7 61.0 3.4 871

H2O equivalent 5.35 Mehlich 1 7.1 198 891 101 40 61.8 3.4 33

Table 2: Total carbon and nutrient content of the organic amendments (means, n=3) Amendment pH C N P K Ca Mg S Al Fe Na Zn B Mn

g/kg

PL 8.7 294.6 35.2 19.9 32.6 29.6 7.5 8.9 5.2 2.6 1.1 0.65 0.05 0.69 PLc 9.7 418.1 35.0 42.6 70.4 55.3 15.5 9.2 9.1 4.3 2.0 1.14 0.10 1.21 286 C. Steiner, et al.

Table 3: Total elements applied into the soil Fertilization level C N P K Ca Mg

t/ha kg/ha

PL 1.5 441.9 52.7 29.9 48.9 44.3 11.3 3.0 883.8 105.4 59.8 97.8 88.6 22.6 6.0 1767.6 210.8 119.6 195.6 177.2 45.2 PLc 1.5 627.2 52.5 63.8 105.7 82.9 23.2 3.0 1254.4 105.0 127.6 211.4 165.8 46.4 6.0 2508.8 210.0 255.2 422.8 331.6 92.8 unfertilized control was also established. All treatments 2.4 Statistical Analysis were arranged in a randomized complete block design with four replicates as detailed in Table 3. Plots were made with SigmaPlot 12 and regressions The experiment was conducted in a heated calculated with Microsoft Excel. SPSS (IBM Corp. Released greenhouse. Five plants of ryegrass (Lolium perenne) were 2011. IBM SPSS Statistics for Windows, Version 20.0. established from seeds. Two to three seeds were planted Armonk, NY: IBM Corp.) was used to test the homogeneity in five locations in each pot on November 11th. After of variances and a general linear model used to analyse germination, the plants were thinned to five plants per variance and the Student-Newman-Keuls post hoc tests pot. Above-ground biomass was sampled for the first time was used to identify significant differences between the 72 days after planting (January 22nd) and thereafter once treatments. The minimum significant difference (MSD) a month for three consecutive harvests (February 19th, was inserted into graphs. March 19th and April 23rd). Water supply was regulated by an automatic trip irrigation system and slightly modified Ethical approval: The conducted research is not related according to variations in demand and to avoid leaching to either human or animals use. of nutrients. 3 Results 2.3 Analysis of litter enrichments, soil, and Our results show that the N contained in carbonized plant samples poultry litter (PLc) is not available for plants and thus clearly limited by N (Figure 1a). Increasing N fertilization Aboveground biomass was dried at 60°C and ground did increase N uptake of the crops except for plants growing before analysis. The soil samples were sieved (2 mm) and in pots fertilized with PLc. At the lower fertilization rates, ground in a ball mill before nutrient analysis. Soil samples plant biomass was higher on PLc at the first harvest than were taken at treatment preparation and at the end of the on PL, but they had the lowest N concentrations in plant experiment. Total nutrient content of the soil, PL and tissues (Figure 1a). There was still residual N available PLc, and aboveground plant biomass were digested with in the soil to support plant growth. The P and K uptake nitric acid (USEPA Method 3050B, (USEPA, 1996) in HP500 of plants fertilized with PLc did slightly increase with microwave vessels and a CEM Mars Express microwave increasing application rates, but the growth was most digestion system and analyzed by Inductively Coupled likely limited by N (Figure 1b and c). Plasma (ICP – Thermo Jarrell-Ash model 61E Thermo Fisher This is corroborated by the finding that plants grew Scientific, Waltham, MA, USA). Plant available nutrients larger when fertilized with PLc than the plants growing in the soils were measured using Mehlich I extraction on the control, but their N concentration in plant tissue (0.05 M HCl + 0.0125 M H SO ) (Mehlich, 1953) and ICP 2 4 was the lowest of all treatments. The biomass production analysis. The pH in soil was measured in 0.01 M CaCl in 2 (Figure 2) and the N concentration in the tissue did not a 1:1 soil solution ratio using a digital pH meter (AR15, increase with increasing fertilization rates. Thermo Fisher Scientific, Waltham, MA). Total C and N in The treatments had no significant influence on total soil, Pl, and PLc were measured by dry combustion (LECO C and nutrient contents of the soil at the end of the study. CNS-2000, St. Joseph, MI, USA). The soil fertilized with mineral fertilizer had the lowest pH The nitrogen contained in carbonized poultry litter is not plant available 287

Figure 1: Regressions of nutrients (N, P, and K) fertilized and cumulative uptake up by ryegrass (Lolium perenne) per kg of soil after 4 conse- cutive harvests. CO = control, PL = poultry litter, MF = mineral fertilizer, PLc = carbonized poultry litter MFc = mineral fertilization based on PLc, means and standard errors, n = 4.

30 30 30 Fertilization Level 1 Fertilization Level 2 Fertilization Level 3 MSD 25 25 25 Co Co Co PL PL MSD PL 20 MF MSD 20 MF 20 MF PLc PLc PLc -1 MFc -1 MFc -1 MFc 15 15 15 g pot g pot g pot

10 10 10

5 5 5

0 0 0 I II III IV I II III IV I II III IV Harvests Harvest Harvest

Figure 2: Cumulative biomass yields (DM g/pot) of 4 consecutive harvests (I-IV) of ryegrass (Lolium perenne) at 3 fertilization levels (1.5, 3 and 6 t/ha) and an unfertilized control CO = control, PL = poultry litter, MF = mineral fertilizer, PLc = carbonized poultry litter MFc = mineral fertilization based on PLc, means and standard errors, n = 4, MSD indicates the minimum significant difference (p ≤ 0.05, Student-New- man-Keuls test). 288 C. Steiner, et al. ab ab ab a ab ab ab ab ab b c ab c Mg 108,5 112,6 120,5 106,7 114,5 112,5 126,9 111,6 118,8 128,0 144,3 122,0 145,4 ab ab abc a abc ab abc ab abc abc bc abc c (ppm) -1 Ca 933,0 939,4 991,2 912,6 973,9 933,8 999,3 930,3 957,4 1014,0 1056,3 972,8 1067,5 , respectively), MF = mineral fertilizer fertilizer = mineral MF , respectively), -1 abc bcd bcd abc ab bcd cd ab abc d e a bcd K Mehlich 1 mg/kg Mehlich 101,5 116,7 121,5 104,5 94,2 114,9 136,1 86,6 106,0 141,0 199,3 77,2 115,7 a a ab a a a bc a ab ab d ab c P 5,32 7,86 10,91 5,69 7,81 8,35 17,31 6,84 9,69 14,05 32,06 12,33 22,28 a a a a a a a a a a a a a Mg -1 1,56 1,67 1,63 1,76 1,81 1,61 1,64 1,78 1,69 1,68 1,75 1,61 1,54 a a a a a a a a a a a a a Ca 0,95 0,98 1,04 1,03 1,08 1,00 1,00 1,06 1,07 1,09 1,11 1,20 1,01 a a a a a a a a a a a a a K 1,91 2,11 2,01 2,16 2,29 2,00 2,05 2,15 2,11 2,13 2,14 1,96 1,93 Total Acid Digestion g kg Digestion Acid Total a a a a a a a a a a a a a P 0,35 0,37 0,39 0,42 0,45 0,37 0,39 0,42 0,45 0,45 0,45 0,35 0,42 a a a a a a a a a a a a a , respectively), CLc1, CLc2, CLc3 = carbonized poultry litter (1.5, 3, and 6 Mg ha (1.5, 3, and litter poultry = carbonized CLc3 CLc2, CLc1, , respectively), Total N -1 -1 1,56 1,58 1,57 1,59 1,59 1,58 1,62 1,54 1,53 1,67 1,64 1,57 1,54 g kg a a a a a a a a a a a a a Total C 19,73 19,70 20,19 20,26 20,12 20,15 20,51 19,61 20,01 20,53 20,96 19,62 19,87 bc bcd bcd ab ab bc d a bc cd e ab bcd O 2 H 5,79 5,82 5,86 5,73 5,75 5,79 5,93 5,66 5,80 5,89 6,07 5,73 5,83 pH 2 bc bcd bcd ab ab bc d a bc cd e ab bcd CaCl 5,19 5,22 5,26 5,13 5,15 5,19 5,33 5,06 5,20 5,29 5,47 5,13 5,23 Treatment CO CL1 CLc1 MF1 MFc1 CL2 CLc2 MF2 MFc2 CL3 CLc3 MF3 MFc3 Soil nutrient contents after 4 harvests of Lolium perenne, Different letters in the same column indicate significant differences (p<0.05) between treatments (Student-Newman-Keuls test, test, (Student-Newman-Keuls treatments between (p<0.05) differences significant indicate column in the same letters Different perenne, Lolium of 4 harvests after contents nutrient 4: Soil Table n = 4) means, (N, P, K, Ca, and Mg) dosed to match CL, MFc = mineral fertilizer (N, P, K, Ca, and Mg) dosed to match CLc. match to Mg) dosed and K, Ca, (N, P, fertilizer = mineral MFc CL, match to Mg) dosed and K, Ca, (N, P, Fertilization level Fertilization I II III CO = unfertilized control, CL1, CL2, CL3 = poultry litter (1.5, 3, and 6 Mg ha (1.5, 3, and litter = poultry CL3 CL2, CL1, control, = unfertilized CO The nitrogen contained in carbonized poultry litter is not plant available 289 and the soil fertilized with PLc the highest. However, in Tagoe et al. (2008) was only 12.3% and did not change due particular at the highest fertilization level, the Mehlich 1 to carbonization, while the original N content was 6.0% extractable nutrients (P, K+, and Mg2+) were significantly and was reduced to 2.6% after carbonization mostly as a higher in pots fertilized with PLc. This again supports the result of the heating of the manure. While the P content conclusion that the plant growth was limited by N and not quadrupled due to carbonization, the Ca2+ content did by the other nutrients. not change much and Mg2+ contents was even reduced. In our study the concentration of the non-volatile elements in the biochar were approximately twice as high as in the 4 Discussion carbonized feedstock, which was expected as shown by Steiner (2016). In order to reduce losses of N and avoid The availability of N supplied with organic fertilizers transferring N into recalcitrant N, Steiner et al. (2010) depends on the C:N ratio and mineralization rates proposed co-composting of N-rich poultry litter with (Probert et al. 2005). Poultry litter has a narrow C:N ratio biochar produced from N-poor feedstock. and about 50% of the total N is reported to mineralize over The plant growth and nutrient uptake on soils the growing season after application (Sistani et al. 2008), fertilized with carbonized poultry litter was clearly hence it is not surprising that N uptake of plants fertilized limited by N availability. Supplementing PLc with mineral with PL was lower than that of plants receiving mineral N fertilization would provide more information on the fertilizer. availability of P and K+ in carbonized poultry litter and The mineralization of biochar depends on should be considered in future studies. carbonization characteristics such as pyrolysis temperature. Higher pyrolysis temperatures produce biochar more recalcitrant against decomposition but 5 Conclusions also with a lower N content (Cantrell et al. 2012; Song and Guo 2012). The hydrolysable organic N decreases Nitrogen in poultry litter carbonized at 500°C is not with higher pyrolysis temperature (Clough et al. 2013) plant available. This has important consequences for and thus the release of N from biochar may depend on its manure management and the sustainable use of natural decomposition. However, when the purpose of biochar resources. If the immobilization of N is a desired objective, production is to stabilize organic matter and sequester pyrolysis might be an appropriate way to achieve this C, then reducing the biochar’s stability to enhance its N goal. The limited resources, force us to find sustainable availability seems counterproductive. ways to recycle nutrients and sequester C. Biochar C Although Chan et al. (2008) attributed yield increases sequestration is promising to lock up C for relatively long- to increases in N availability, this seems not to be the case time scales. However, this deceleration of mineralization in our study. Chan et al. (2008) applied 200, 500, and 1000 which is a positive consequence for the global C cycle is kg of N per ha with the carbonized poultry manure (10, less beneficial when considering the N bioavailability of 25, and 50 t/ha, respectively) and an additional mineral biochars with a relatively high N content. N fertilization of 100 kg/ha increased yields significantly independent from the rate of biochar applied. The average Acknowledgements: The authors acknowledge the N concentration in plant tissue was 2.4% with, but only financial support of the US DOE, State of Georgia, and 1.7% without the additional mineral N fertilization. the University of Georgia experiment station for partial Therefore, in our view, the results of Chan and colleagues support of this work through the Biorefinery and Carbon corroborate our findings that N in carbonized poultry Cycling Program. We thank Dwight Fisher (ARS retired) for litter is not available. his valuable advice, Richard Speir and Donald Lakly for Stronger evidence that the N in carbonized poultry making the biochar and the greenhouse manager Pamela manure is plant available is provided by Tagoe et al. Lewis and Mark van Iersel. We are grateful for the soil (2008). They used 15N labelled poultry manure and found which was provided from Nathan Melear. a 15N recovery of 17,6% and 8.9% for carbonized poultry manure at application rates of 50 and 100 kg N per ha, Conflict of interest: Authors state no conflict of interest. respectively. The uptake of N by plants fertilized with dried manure was only slightly higher. However, this poultry manure is different from the litter (bedding) used in our study. The original C content of the manure used by 290 C. Steiner, et al.

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