Previous Article in Journal
Estimation Method of Leaf Nitrogen Content of Dominant Plants in Inner Mongolia Grassland Based on Machine Learning
 
 
Search for Articles:
Title / Keyword
Author / Affiliation / Email
Journal
Article Type
 
 
Advanced Search
 
Section
Special Issue
Volume
Issue
Number
Page
 
Journals
Nitrogen
Volume 6
Issue 3
10.3390/nitrogen6030071
nitrogen-logo
Submit to this Journal Review for this Journal Propose a Special Issue
► Article Menu

Article Menu

share Share announcement Help format_quote Cite question_answer Discuss in SciProfiles
first_page
settings
Order Article Reprints
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:
Background:
Article

Effect of Biochar on the Nitrogen Mineralization of Commercial Organic Fertilizers in Both Mineral Soil and Organic Potting Media

by
James Johnathan Pulliam
1,*,
Kate Cassity-Duffey
1 and
Miguel Cabrera
2
1
Horticulture Department, University of Georgia, 1111 Miller Plant Sciences Building, Athens, GA 30602, USA
2
Crop and Soil Sciences, University of Georgia, 3111 Miller Plant Sciences Building, Athens, GA 30602, USA
*
Author to whom correspondence should be addressed.
Nitrogen 2025, 6(3), 71; https://doi.org/10.3390/nitrogen6030071
Submission received: 17 July 2025 / Revised: 10 August 2025 / Accepted: 19 August 2025 / Published: 21 August 2025
Browse Figures
Versions Notes

Abstract

As interest in biochar as a soil amendment increases, the co-application of biochar and fertilizer warrants investigation. Biochar may improve soil properties, affect crop yields, and mitigate environmental impacts, but more work is needed to determine its effect on nitrogen (N) cycling from commercially available organic fertilizers. A 102 d laboratory incubation was conducted to better understand the effect of three rates of biochar (0%, 5%, and 10%) on net N mineralized from (1) mineral soil (Cecil sandy loam), (2) organic peat-based potting media, and (3) two commercial organic fertilizers (feather meal and meal-based pellet mix) applied to the mineral soil or the potting media. After 102 d, the biochar treatments did not affect net N mineralized from the mineral soil but decreased (from 190 to −286.9 mg N kg−1) the net N mineralized from the potting media, likely due to N immobilization. Biochar applied at 5 or 10% did not affect the amount of organic N mineralized from the organic fertilizers applied to potting media (average 58.9%), but biochar at 5% decreased from 46.5 to 28.1% of organic N mineralized from the organic fertilizers applied to mineral soil.

1. Introduction

From 2011 to 2021, the United States experienced a nearly 80% increase in certified organic cropland reaching over 1.4 million hectares [1]. Half of organic producers identify soil fertility as an obstacle of production, so there is a need to better understand nutrient cycling in these complex systems for both organic field and greenhouse production [2]. Organic growers use a wide range of materials to meet nutrient demands including commercially available animal and plant meal-based organic fertilizers, manures, and composts [3]. While commercial USDA-certified organic fertilizers are produced to create consistent nutrient availability for each product, organic fertilizers are naturally derived, which causes variations in composition, nutrient availability, and timing of release based on material composition, manufacturing processes, and size [4,5]. Further, these plant nutrients in organic fertilizers are primarily present in organic forms, requiring the process of mineralization to produce plant-available inorganic forms. This mineralization process is largely influenced by organic fertilizer characteristics, soil properties, and environmental conditions [6,7,8,9,10]. A study examining over 45 organic fertilizers and amendments (animal wastes, commercially produced organic fertilizers, and composts) found that plant-available nitrogen varied from 1 to 93% of the applied organic nitrogen, with fertilizer characteristics driving the amount and rate of nitrogen (N) mineralization [6]. Given that N is often the most limiting nutrient in organic systems, the importance of understanding plant-available N release from commercial organic fertilizers and the potential mechanisms of loss (leaching, volatilization, immobilization, and denitrification) cannot be understated [11,12].
Due to variations in organic fertilizer composition and rate of release, research has been conducted to determine factors that drive N mineralization. Previous works have concluded that soil texture [13] and temperature [7] have minimal impacts on the mineralization of commercial organic fertilizers (feather meal, pellet mix, and pelleted poultry litter). One field study examining ammonia (NH3) loss from four organic fertilizers found that the different fertilizers lost different amounts [14]. Erwiha et al. [14] determined that NH3 loss from solid fertilizers (blood and feather meal) averaged 29% of total N when surface-applied, whereas liquid fertilizers (fish emulsion and cyano-fertilizer) applied through drip irrigation showed losses comparable to unfertilized treatments. As organic greenhouse production increases, efforts to identify types of organic fertilizers, application rates, and environmental conditions to optimize production have been made. Burnett et al. [15] identified that publications on relevant fertility and substrate management remain a barrier in organic greenhouse production. Goh [16] examined fast- and slow-release fertilizers in five different peat- and sand-based media and found that N from the fast-release inorganic fertilizers (urea and nitrolime) had a nearly complete recovery of 83–100%, while the organic fertilizer (poultry litter) only recovered 28–42% of N over a three-month period. More recently, Dion et al. [17] examined the release of N from five organic fertilizers (pelleted poultry manure, blood, feather, alfalfa, and shrimp meals) in both soil and organic peat substrate. They determined a N mineralization rate ranging from 34 to 93% of applied N, with potting media generally having higher amounts of mineralization. The authors placed an emphasis on the impacts of the material biochemical properties and the microbial communities they foster in the growing media or soil.
For both organic and conventional growers, biochar has gained interest as a soil amendment. Biochar has shown the potential to reduce some of the environmental impacts of excess nutrients and to improve soil characteristics and crop yield, but the results have been inconsistent and can differ due to biochar composition, soil properties, plant cultivar, and environmental conditions [18,19,20,21]. Biochar is a carbon-rich material made from a wide variety of feedstocks (often waste products) including animal manure and plant biomasses. With an increase in biomass conversion plants used for electricity production, biochar waste products have become increasingly available. The materials sourced to produce biochar undergo the process of pyrolysis which subjects the feedstocks to low levels of oxygen at temperatures ranging from 400 to 850 °C [22,23]. Due to the range of production practices and feedstocks, the physical and chemical characteristics of biochar can be highly variable [24,25]. A review by Clough et al. [26] highlights the ability of biochar (depending on feedstock and pyrolysis temperature) to reduce N leaching through nitrate (NO3) and ammonium (NH4) adsorption, spur immobilization, denitrification, and ammonia volatilization, and moderate nitrous oxide (N2O) emissions during and following N inputs including manure.
The effect of biochar application on N mineralization has been determined for some soils and N fertilizers, but data are lacking for commercial organic fertilizers. In a 65 d incubation study using wheat biochars derived from two pyrolysis methods (fast and slow pyrolysis), the application of fast pyrolysis biochar to a sandy loam soil resulted in 43% immobilization of soil mineral N, while the slow pyrolysis biochar caused a 7% increase in net N mineralization [27]. More long-term research in the field has shown the application of a hardwood biochar to a wheat plot (fertilized with nitrogen–phosphate, ammonium nitrate, and urea) had negligible findings [28]. They determined that the first three months following biochar application resulted in increased rates of net N mineralization, but no difference was reported fourteen months from application [28]. The effect of biochar in greenhouses has been studied, showing that biochar made from different materials (wood and plant residues) can impact the phenotypes of individual tomato cultivars (Solanum lycopersicum L.). Even biochar produced from the same feedstock has the potential to alter phenotypes in three different tomato cultivars (‘Oregon Spring’, ‘Heinz 2653’, and ‘Cobra F1’) [18].
Both biochar products and organic fertilizers have independently been researched, but few have determined the effect of both materials being applied simultaneously on N mineralization, especially for commercially produced organic fertilizers. Most of the work conducted with biochar coapplied with fertilizer has been with inorganic fertilizers, raw manures/biosolids, and field soils. The co-application of these two materials has shown (1) variable yield increases (on average, higher yield increases when applied to unfertilized control), (2) insignificant effects of biochar rate, and (3) most benefits in acidic soils [20]. Through the limited studies of applying biochar with manure, results have shown dairy manure alone increases carbon dioxide (CO2) and nitrous oxide emissions (N2O) while having increased net N mineralization. Biochar alone did the opposite, reducing gas emissions and minimizing net N mineralization [29]. When materials were combined, a maximized net N mineralization was experienced without increasing gas emissions [29]. Poultry litter, a common organic nutrient source for southeastern U.S. growers, experienced up to 63% reduction (surface-applied) and up to 60% reduction (incorporated) in N-losses from ammonia (NH3) volatilization when amended with acidified biochar during a three-week incubation study [30]. As organic greenhouse production expands, fertility and substrate management remain a challenge for growers [31]. The lack of literature on the application of biochar in combination with commercially available organic fertilizers highlights the need for more data. Therefore, the objectives of this study were to evaluate the effect of biochar rates on N mineralization from (1) mineral soil, (2) organic potting media, and (3) two commercial organic fertilizers applied to mineral soil or organic potting media through a 102 d laboratory incubation.

2. Materials and Methods

2.1. Initial Soil and Material Characteristics

A Cecil sandy loam (fine, kaolinitic, thermic Typic Kanhapludult; [32]) from certified organic land at the University of Georgia Durham Horticulture Farm, Watkinsville, GA (33.88689° N, 83.41941° W), and certified organic Sphagnum peat-based potting media (Sun Gro Horticulture, Agawam, MA, USA) were used to conduct this experiment. The soil and potting media were collected two weeks prior to the start of the incubation and were stored at 23 °C with frequent aeration. Initial gravimetric water content was determined by drying the soil at 105 °C and the potting media at 65 °C for 48 h [33,34]. For the soil, the maximum gravimetric water holding capacity (maxWHC) was estimated by saturating soil and draining over a sand bath for 48 h [13,35]. The maxWHC of the potting media was determined by placing a known volume of media in metal rings covered by netting, saturating the media, allowing free drainage of water for 48 h, and weighing again for moisture content [36]. Bulk density was determined to be 1.36 g cm−3 for the soil and 0.17 g cm−3 for the potting media (packed to mimic typical pots) [37]. Initial soil pH was measured in 0.01 mol L−1 calcium chloride (CaCl2) [38], routine nutrient analysis was conducted at the University of Georgia Agricultural and Environmental Services Laboratories (UGA AESL) [39,40], and total N and carbon (C) contents were determined by dry combustion ([41]; Table 1). Cation exchange capacity (CEC) was determined at the UGA AESL by Mehlich-1 extraction and titration with calcium hydroxide (Ca(OH)2) [42]. On day one of the study, initial contents of ammonium (NH4-N) and nitrate (NO3-N) were measured by potassium chloride (KCl) extraction using 1 mol L−1 with 1:8 ratio of soil–KCl [43]. Aqueous KCl extracts were then analyzed for total inorganic N (TIN; both NH4-N and NO3-N) using an ammonia analyzer (model TL-2800, Timberline Instruments, Boulder, CO, USA) based on gas diffusion and conductivity principles where NO3-N is determined through zinc reduction [44,45].
Two commonly used organic fertilizers, feather meal (14.3N-0.6P2O5-0.1K2O; Mason City By-Products, Mason City, IA, USA) and pellet mix (feather meal, blood meal, bone meal, and sulfate of potash) (10.6N-2.6P2O5-10.5K2O; All Season Organic Fertilizer; Nature Safe, Irving, TX, USA), as well as a commercial biochar product (Qualterra, Pullman, WA, USA), were used for the long-term incubation.
The biochar was derived from wheat straw and softwood ash, and the pyrolysis temperature is 800 °C. Fertilizers and the biochar underwent routine analysis at University of Georgia AESL for total C, N, phosphorus, potassium, calcium, magnesium, sulfur, manganese, iron, aluminum, boron, copper, zinc, and sodium [39,40]. In addition to routine analysis, the fertilizers were extracted using 2 mol L−1 KCl on a 1:200 ratio of fertilizer–KCl and analyzed for initial NH4-N and NO3-N conductimetrically (Table 2; [44,45]).

2.2. Incubation

Soils were adjusted to reach and maintained at 70% of maxWHC (0.16 g H2O g dry soil−1 for Cecil and 2.28 g H2O g dry media−1 for potting media) and allowed to sit for two days prior to incubation initiation. Two incubation substrates (soil and potting media) were factorially combined with three fertilizer treatments (no fertilizer, feather meal, and pelleted mix) and three biochar rates (0%, 5%, 10%) to generate a total of 18 treatments that were replicated three times and arranged in a randomized complete block design. Treatments of soil or potting media with three rates of biochar were considered “control” treatments to calculate net N mineralized from organic fertilizers applied to soil or potting media with the three rates of biochar. The experimental units were 0.94 L jars with 340 g of dry Cecil soil (394.4 g wet equivalent) or 42 g of dry potting media (137.8 g wet equivalent). Recognizing the vast differences between field soil and potting media, these masses were chosen to attain an equal volume of material in each jar (250 cm−3). The amount of fertilizer applied was 0.19 mg N cm−3 for feather meal (137.5 mg N kg−1 dry Cecil soil and 1113.4 mg N kg−1 dry potting media) and 0.18 mg N cm−3 for pellet mix (132.5 mg N kg−1 dry Cecil soil and 1072.6 mg N kg−1 dry potting media). The biochar amendment was added on a volume basis at three rates, 0%, 5% (3.75 g), and 10% (7.5 g). The amount of C from biochar per jar was calculated by multiplying the mass of biochar added to each treatment by the % total C of biochar. The biochar-derived C per jar calculation was used to understand the C and N dynamics following the addition of a major C-source at the start of the incubation. Experimental units were placed in an incubator at 30 °C and aerated daily during the first week and then every three to four days throughout the experiment. Soil water content was maintained by weighing the experimental units and replacing the weight loss with deionized water. On d 1, 3, 7, 10, 21, 35, 50, 72, and 102, 5 g subsamples were taken from all treatments and extracted for inorganic N by shaking in 40 mL of 1 mol L−1 KCl for 30 min. Inorganic N of the supernatant (NH4-N and NO3-N) was analyzed as described above.

2.3. Carbon Indices

A water-soluble C extraction was conducted on both substrates (Cecil soil and potting media) as well as the biochar to estimate the amounts of labile C. The amounts extracted with 40 mL of deionized water for three hours were 5 g for the Cecil soil and potting media, and 2 g for the biochar. In addition to the soluble C indices, the organic potting media with 0% and 10% biochar were evaluated for CO2 respiration at 25 °C over a 7 d period by placing 30 g of media in a 0.9 L jar that contained a CO2 trap 40 mL, 0.1M sodium hydroxide (NaOH). On day 7, 20 mL subsamples from all five NaOH traps were taken and analyzed for CO2. Both soluble C and CO2 were quantified using a total organic carbon analyzer (model TOC-L with ASI-L autosampler, Shimadzu Corporation, Kyoto, Japan).

2.4. Ammonia Volatilization and Soil PH

To evaluate the amount of ammonia (NH3-N) volatilized from organic fertilizers and soils, sulfuric acid traps were placed in each of the experimental units. Traps consisting of 40 mL of 0.1 mol H2SO4 L−1 were replaced on the same days as KCl extractions (1, 3, 7, 10, 21, 35, 50, and 72 d after application) and were removed from jars on day 84 and not replaced. Once traps were removed from jars, they were brought to their original volume using deionized water and then vortexed to mix thoroughly. The traps were subsampled (20 mL) and analyzed for NH3-N using the Timberline unit and procedure described above. Given the impact pH has on ammonia volatilization [46], pH was determined on day 0 in soil and biochar mixtures and then in all 54 experimental units (three replications per treatment) on day 60. The pH was measured in 0.01 mol CaCl2 L−1 on a 1:4 soil–CaCl2 ratio [38].

2.5. Nitrogen Mineralization Calculation and Statistical Analysis

On each extraction day, net N mineralized in “control” treatments was calculated by subtracting initial inorganic N in soil/media and initial inorganic N in biochar (when applied) from the final inorganic N measured at the extraction day. The net N mineralized from feather meal and pelleted mix was calculated by subtracting inorganic N at a given extraction day from inorganic N in “control” treatments on the same extraction day, where “control” treatments are the corresponding soil or potting media plus the percent biochar applied.
For fertilized treatments, the net N mineralized is presented as a percentage of the organic N applied calculated by dividing the net N mineralized (mg N kg−1 dry soil) by the total organic N applied (Total N-inorganic N; mg N kg−1 dry soil) and multiplying by 100.
For each substrate (soil/potting media), a one-way analysis of variance (ANOVA) was conducted with R [47] to evaluate the effect of biochar and substrate on net N mineralized. When ANOVA indicated significance, Tukey’s HSD was used to separate means at p < 0.05. The models were run using the lm function from the stats package in R version 4.2.1 [47].

3. Results

3.1. Soil and Fertilizer Analysis

The organic peat-based potting media contained 34.9% C and 0.9% N with a CEC of 100.6 mEq 100 g−1. The Cecil soil had 1.6% C and 0.1% N with a CEC of 6.1 mEq 100 g−1 (Table 1). The C:N of the Cecil soil was 11.6, while that of the organic potting media was higher at 38.8. The potting media had a slightly higher pH than the Cecil soil (5.3 vs. 5.1) (CaCl2 pH). The peat-based potting media are on par with other peat-based media when considering initial pH and % N [17]. These differences in values between potting media and field soil are expected, as their physical and chemical properties are largely dissimilar and should be considered when looking at effects of the N mineralization from both materials and the effects of biochar application. Of these differences, the C:N ratio and initial N concentrations are often considered key indicators of ultimate N release from NH4-N and NO3-N, especially in potting media [16,34]. The feather meal and pellet mix had a C:N ratio < 4 due to higher N contents (14.3% and 10.6%, respectively), with the initial inorganic present primarily in the form of NH4-N (Table 2). The biochar had a pH of 11.8 and contained 0.4% N and 45% C, lending itself to a high C:N ratio of 125 with all inorganic N in the form of NH4-N. The wheat straw biochar used in the current study is on the higher end of C:N and pH values compared to other wheat straw biochars [27,48].

3.2. Effect of Biochar on N Mineralization from Soil and Potting Media

In the control Cecil soil, the amount of net N mineralized from soil organic matter at 102 d (42.8 mg inorganic N kg −1 dry material) was similar to that in other studies [6,7] and was not affected by the addition of biochar (Table 3). While no significant differences were determined at 102 d, significant differences were observed on day 10 when 10% biochar treatment mineralized significantly more N than the treatment with 0% or 5% biochar (Figure 1). These results indicate that the addition of biochar to Cecil soil may have a small impact right after application but an overall minimal impact on the long-term N mineralization from the native soil N pool.
In contrast to the mineral Cecil soil, N mineralization in the organic peat-based potting mix showed a reduction in N mineralization or possible immobilization of N with the addition of biochar. At the start of the incubation, the organic potting media responded similarly to the Cecil soil, where the 10% biochar treatment mineralized significantly more N than 0% and 5% biochar treatments during the first 3 days (Figure 2). However, this trend did not continue through the incubation, with significantly more net N mineralized in the 0% biochar treatment for the remainder of the 102 days compared to the 5% and 10% treatments (Figure 2). By day 35, the 0% biochar treatment mineralization remained stable throughout the incubation until it began to slightly increase after day 72 (Figure 2). While the 0% biochar potting media treatment remained stable overall, the 5% and 10% biochar treatments had significantly less N mineralized compared to the 0% treatment after d 35, and the trend continued for the remainder of the incubation period. At day 102, the net N mineralized was 190, −286.9, and −155.5 mg inorganic N kg−1 dry media for the 0%, 5%, and 10% biochar treatments, respectively (Table 3). While the values of total inorganic N (TIN) present in potting media (918, 412.5, and 440.8 mg N kg−1 dry media for 0%, 5%, and 10% biochar treatments, respectively) are much larger than those for the Cecil soil, they are consistent with other findings using peat-based potting media accounting for their higher initial N contents [16,17]. At the start of the current study, the potting media had almost three times the amount of TIN per unit of C added from biochar when compared to the Cecil soil (Table 1). This higher TIN per unit of C added may have contributed to the significant decrease in net N mineralized in the organic potting media when amended with biochar. In a study using peat media amended with biochar by Messiga et al. [49], they determined a rapid release of inorganic N (mostly NH4) immediately followed by a sharp decline. In contrast, Ref. [17] saw little difference in the mineralization kinetics from organic fertilizers in mineral soil and media although the peat-based media had higher net N mineralized overall.
The significant decrease in net N mineralized in the potting media with biochar treatments was further investigated by measuring water-soluble C and soil respiration. The amount of soluble C in the potting media was nearly 15 times the amount of soluble C estimated in the Cecil soil (Table 4). In addition to the substrate-derived soluble C, the biochar contributed 120.5 and 242 mg of soluble C per kg of dry substrate in the 5% and 10% biochar treatments, respectively. During a 7 d incubation, our results show over twice the amount of CO2 evolved in the 10% biochar treatment compared to the 0% biochar treatment. The amount of CO2 emission was 630.1 and 1482 mg CO2 kg−1 of dry potting media for the 0% and 10% biochar treatments, respectively (Table 4). These results were on par with those found in other studies examining the combination of peat and biochar [49]. Because the potting media with 0% biochar did not show the steep reduction in TIN seen in the 5% and 10% biochar treatments, we hypothesize the biochar addition to potting media is potentially responsible for the decrease in N mineralized. The estimate of soluble C, coupled with the elevated respiration seen in the 10% biochar potting media treatment, suggests the drop in TIN observed in potting media was likely due to N immobilization. The easily degradable C contributed by the biochar could have triggered increased decomposition and respiration by the microbial communities and, thus, immobilization of the plentiful NO3-N provided by the potting media [50]. While potting media shows a dramatic loss of TIN after the application of biochar, the mineral Cecil soil does not, which could be explained by the simple fact that there is little TIN in the mineral soil to begin with compared to organic potting media. Another more complex explanation of the biochar’s minimal impact on the mineral soil (Cecil) could be the physical interaction that happens between biochar and clay particles forming organo-mineral complexes potentially protecting biochar surfaces from degradation [51]. Clarke and Cavigelli [34] observed various compost/peat mixtures and suggested that media mixtures with a C:N > 25 have a mineralization potential of 0, which could explain the biochar with a C:N of 125, negatively impacting net N mineralization. While our study did not use compost, the previous results provide insight into the N dynamics when C-rich sources are mixed with peat and other materials with high C:N ratios. Additionally, a study using peat–sand–sawdust medium saw average immobilization rates of 54%, with some cases having 81% N immobilized [36]. Since the C:N ratio of sawdust is responsible for N immobilization in the peat mixture, it can be inferred that the potting media and biochar with high C:N ratios (38.7 and 125, respectively) used in the current study could favor considerable amounts of N immobilization compared to the mineral soil. Because the current study did not directly measure N immobilization, future work confirming these hypotheses is needed.
While our results support the idea of N-loss via immobilization, denitrification remains a potential path for additional N-losses. Although the soil and potting media were aerated every 3–4 days, other factors could have contributed to potential denitrification. Due to the high soluble C and water content of potting media, and the addition of the C-rich biochar, the combination of potting media and biochar bodes well for the process of denitrification [52]. Denitrification was not measured in the current study, but other research has shown variable results when it comes to biochar’s impact on N2O emissions. The variability lies in the type of biochar, how much biochar, and what material the biochar is amended with. Messiga et al. [49] found that peat mixed with biochar resulted in CO2 and N2O emissions three times higher than that of peat alone. The high emissions were attributed to mineralization of easily degradable C in biochar used in their study. The results were similar to those in other studies, which see a trend of decreased inorganic N, whether it be NH4 or NO3, when biochar is amended into peat-based media and other materials [53,54]. Some works suggest that the release of N2O is not to blame; rather, a slowed nitrification cycle caused by the swift adhesion of NH4 onto the biochar results in lower concentrations of NO3 [53]. The interaction between biochar and the soil in which it was amended highlights the differences between soil and potting media’s physical and chemical characteristics.

3.3. Effect of Biochar on Mineralization from Fertilizers

In both the field soil and the organic potting media, most N mineralization from feather meal- and pellet meal-based fertilizers occurred by day 10, with slower release measured throughout the remainder of the incubation (Figure 3). By day 102, the percent net N mineralized (based on the amount of organic N applied) in the no-biochar treatment was 42.3 and 68.7% for the feather meal and 46.5 and 57.8% for the pellet mix in the Cecil soil and potting media, respectively (Table 5). For the mineral Cecil soil, no significant differences in net N mineralized from the feather meal were determined between biochar treatments, with an average of 42.2% of organic N mineralized during the study (Table 5). In contrast, there were significant differences in net N mineralized from the pellet mix in the mineral soil. The percentage of organic N mineralized from the pellet mix in the Cecil soil was 46.5, 28.1, and 45.5% for the 0%, 5%, and 10% biochar treatments, respectively (Figure 3). By day 102, 5% biochar, pellet mix treatment mineralized significantly less N than the 0% biochar, pellet mix treatment. The 5% biochar, pellet mix treatment had high variability across reps throughout the study, which could have been attributed to the lower values measured (Table 5).
While the 5% biochar, pellet mix treatment in Cecil soil was significantly less in this experiment, further research is needed across different soils and environmental conditions to see if this trend persists.
For the potting media, net N mineralization from both organic fertilizers had no significant difference between biochar treatments and averaged 63.8% for feather meal and 54.1% for pellet mix of organic N applied (Figure 3). These values for % N mineralized of feather meal are on the lower end, while those from pellet mix are comparable to previous works [6]. Overall, the rate of N release and the pattern of mineralization from both organic fertilizers were similar in both peat-based organic potting media and mineral soils observed by Dion et al. [17]. Their results showed an average greater net N mineralized in the peat-based media compared to soil and identified that due to the lower bulk density of potting media, fertilizer applications on a mass basis are also greater, which they determined caused a more noticeable effect on the soil bacterial communities [17]. While our results show overall higher net N mineralization in the potting media, the impact of biochar on the N mineralization of organic fertilizers is minor and yields similar % net N mineralization in both materials.
Commonly, the C:N ratios of soil amendments serve as a predictor of N mineralization and ultimately plant-available N [9], but Cannavo et al. [55] determined that the C:N ratio of the growing media tends to eclipse the C:N of fertilizers, placing emphasis on the composition of growing media as a driver for N mineralization as opposed to the C:N of its amendments. They also saw the nitrification process peak at 28 °C and at 50–76% water-filled porosity for their examined peat-based growing media amended with organic fertilizers, and the current study was conducted at 30 °C and 70% WHC. Given that these environmental conditions are similar to the optimal conditions for mineralization and nitrification processes in field soils, it is not surprising that our results of % N mineralized from the organic fertilizers are comparable across both the Cecil soil- and peat-based organic potting media. Our results differ from the work of Paillat et al. [56], who documented an accumulation of NH4-N in peat-based growing media following the application of an organic fertilizer. They attributed this accumulation of NH4-N to weak nitrification due to suboptimal pH conditions for nitrifying microorganisms. Our results show an accumulation of NH4-N in the first seven days following fertilization with almost all N being in the NO3-N form for the remainder of the incubation. The difference in N forms could be due to the initial pH of the growing media. Since pH is a driving force for nitrifier activity, the growing media in the current study having a slightly more neutral pH could provide a more optimal environment for nitrifiers, thus leading to more NH4-N being transformed to NO3-N. Additionally, the application of the alkaline biochar (pH = 11.84) could contribute to the pH effect on the nitrification process.

3.4. pH Impact NH3 Volatilization

Ammonia losses could be expected to increase as biochar application increases, given the alkalinity of biochar, as reported in a short-term incubation by Schomberg et al. [57]. However, no ammonia volatilization was measured from any of the biochar treatments (0%, 5%, and 10%) in either material (Cecil soil and organic potting media) or fertility treatment (no fertility, feather meal, and pellet mix). Cassity-Duffey et al. [6] showed similar results when examining organic fertilizers in Cecil soil. As shown in Table 6, the pH of control soils (unfertilized) ranged from 4.6 to 6.8 on day 0 and from 4.7 to 7.1 on day 60. The 0% biochar treatment had the most acidic pH value, and the 10% biochar had the most neutral pH value. Similarly to the control soils, the two organic fertilizers did not have a significant impact on pH, with values (CaCl2) ranging from 4.3 to 6.9 across biochar treatments for both fertilizers. It is worth noting that the pH values between the Cecil soil and the organic potting media have little variation on either day pH was measured and could aid in explaining the similar % N mineralized between the two materials. On day 60, pH values between all biochar treatments for control and fertilized soils were significantly different (p < 0.001), with pH values increasing as biochar rate increased. These increases in pH could favor the nitrification process and ultimately impact the net N mineralized from the mineral soil, potting media, and organic fertilizer.

4. Conclusions

The addition of wheat straw biochar (pyrolysis temperature 800 °C) to Cecil soil showed little impact on the soil nitrogen mineralization during our 102 d incubation study. In contrast, the addition of biochar noticeably decreased net N mineralization from the organic potting media, likely due to N immobilization. While the biochar had a considerable influence on mineralization in the organic potting media, the % N mineralized from both organic fertilizers was less affected in both the Cecil soil and potting media. By day 102 of the incubation, % N mineralized from feather meal across both Cecil soil and potting media, as well as all biochar treatments, was 42.1 to 68.7% of the organic N applied. The range of % N mineralized from the pellet mix across all materials and treatments was 28.1–57.8% of the organic N applied. Our results show little impact of biochar on the mineralization of commercially available organic fertilizers, but a more in-depth examination of the mechanisms by which biochar impacts N transformations following organic fertilization in both field and potting media is needed. The current study saw no measurable ammonia volatilization that was expected from the increase in pH due to the alkalinity of the biochar, highlighting the need to center on other pathways of N-loss following the addition of biochar to soils that are organically fertilized. Further studies are needed to evaluate the results of biochar applications with commercial organic fertilizers as impacts vary with each biochar product.

Author Contributions

Conceptualization, K.C.-D. and M.C.; methodology, K.C.-D. and M.C.; software, J.J.P.; formal analysis, J.J.P. and K.C.-D.; investigation, J.J.P., K.C.-D. and M.C.; resources, K.C.-D. and J.J.P.; data curation, J.J.P.; writing—original draft preparation, J.J.P.; writing—review and editing, J.J.P., K.C.-D. and M.C.; visualization, J.J.P., K.C.-D. and M.C.; supervision, K.C.-D. All authors have read and agreed to the published version of the manuscript.

Funding

This research received no external funding.

Data Availability Statement

The data shown in this study are available upon request from the corresponding author.

Conflicts of Interest

The authors declare no conflicts of interest.

References

  1. USDA ERS—Organic Agriculture. Available online: https://www.ers.usda.gov/topics/natural-resources-environment/organic-agriculture/#:~:text=According%20to%20USDA%2C%20National%20Agricultural,percent%20(to%2017%2C445%20farms)%20over (accessed on 11 January 2024).
  2. Snyder, L.; Schonbeck, M.; Vélez, T.; Tencer, B. Outcomes and Recommendations from the 2020 National Organic & Transitioning Farmer Surveys and Focus Groups; Organic Farming Research Foundation: Santa Cruz, CA, USA, 2022. [Google Scholar]
  3. Power, J.F.; Papendick, R.I. Organic sources of nutrients. In Fertilizer Technology and Use; Wiley: Hoboken, NJ, USA, 2015; pp. 503–520. [Google Scholar] [CrossRef]
  4. Card, A.; Whiting, D.; Wilson, C.; Reeder, J.; Goldhamer, D.; Oleszak, H. CMG Gardennotes #234 Organic Fertilizers—Colorado Master Gardener. Organic Fertilizers. 2015. Available online: https://cmg.extension.colostate.edu/Gardennotes/234.pdf (accessed on 9 February 2024).
  5. Sánchez, E.; Richard, T. Using Organic Nutrient Source; The Pennsylvania State University: Pennsylvania, PA, USA, 2013; Available online: https://extension.psu.edu/using-organic-nutrient-sources (accessed on 9 February 2024).
  6. Cassity-Duffey, K.; Cabrera, M.; Gaskin, J.; Franklin, D.; Kissel, D.; Saha, U. Nitrogen mineralization from organic materials and fertilizers: Predicting N release. Soil Sci. Soc. Am. J. 2020, 84, 522–533. [Google Scholar] [CrossRef]
  7. De Jesus, H.I.; Cassity-Duffey, K.; Dutta, B.; da Silva, A.L.B.R.; Coolong, T. Influence of Soil Type and Temperature on Nitrogen Mineralization from Organic Fertilizers. Nitrogen 2024, 5, 47–61. [Google Scholar] [CrossRef]
  8. Geisseler, D.; Smith, R.; Cahn, M.; Muramoto, J. Nitrogen mineralization from organic fertilizers and composts: Literature survey and model fitting. J. Environ. Qual. 2021, 50, 1325–1338. [Google Scholar] [CrossRef] [PubMed]
  9. Lazicki, P.; Geisseler, D.; Lloyd, M. Nitrogen mineralization from organic amendments is variable but predictable. J. Environ. Qual. 2020, 49, 483–495. [Google Scholar] [CrossRef] [PubMed]
  10. Tei, F.; de Neve, S.; de Haan, J.; Kristensen, H.L. Nitrogen management of vegetable crops. Agric. Water Manag. 2020, 240, 106316. [Google Scholar] [CrossRef]
  11. Berry, P.M.; Sylvester-Bradley, R.; Philipps, L.; Hatch, D.J.; Cuttle, S.P.; Rayns, F.W.; Gosling, P. Is the productivity of organic farms restricted by the supply of available nitrogen? Soil Use Manag. 2002, 18, 248–255. [Google Scholar] [CrossRef]
  12. Möller, K. Soil fertility status and nutrient input–output flows of specialised organic cropping systems: A review. Nutr. Cycl. Agroecosyst. 2018, 112, 147–164. [Google Scholar] [CrossRef]
  13. Cassity-Duffey, K.; Cabrera, M.; Franklin, D.; Gaskin, J.; Kissel, D. Effect of soil texture on nitrogen mineralization from organic fertilizers in four common southeastern soils. Soil Sci. Soc. Am. J. 2020, 84, 534–542. [Google Scholar] [CrossRef]
  14. Erwiha, G.M.; Ham, J.; Sukor, A.; Wickham, A.; Davis, J.G. Organic Fertilizer Source and Application Method Impact Ammonia Volatilization. Commun. Soil Sci. Plant Anal. 2020, 51, 1469–1482. [Google Scholar] [CrossRef]
  15. Burnett, S.E.; Mattson, N.S.; Williams, K.A. Substrates and fertilizers for organic container production of herbs, vegetables, and herbaceous ornamental plants grown in greenhouses in the United States. Sci. Hortic. 2016, 208, 111–119. [Google Scholar] [CrossRef]
  16. Goh, K.M. Evaluation of potting media for commercial nursery production of container-grown plants. N. Z. J. Agric. Res. 1979, 22, 163–171. [Google Scholar] [CrossRef]
  17. Dion, P.P.; Jeanne, T.; Thériault, M.; Hogue, R.; Pepin, S.; Dorais, M. Nitrogen release from five organic fertilizers commonly used in greenhouse organic horticulture with contrasting effects on bacterial communities. Can. J. Soil Sci. 2020, 100, 120–135. [Google Scholar] [CrossRef]
  18. Isaac, D.; Labbancz, J.; Knowles, N.R.; Tenic, E.; Horgan, A.; Ghogare, R.; Dhingra, A. Biomass Source of Biochar and Genetic Background of Tomato Influence Plant Growth and Development and Fruit Quality. Horticulturae 2024, 10, 368. [Google Scholar] [CrossRef]
  19. Lehmann, J.; Czimczik, C.; Laird, D.; Sohi, S. Stability of biochar in soil. In Biochar for Environmental Management; Routledge: Oxfordshire, UK, 2012; pp. 215–238. [Google Scholar]
  20. Bai, S.H.; Omidvar, N.; Gallart, M.; Kämper, W.; Tahmasbian, I.; Farrar, M.B.; Singh, K.; Zhou, G.; Muqadass, B.; Xu, C.Y.; et al. Combined effects of biochar and fertilizer applications on yield: A review and meta-analysis. Sci. Total Environ. 2022, 808, 152073. [Google Scholar] [CrossRef] [PubMed]
  21. Tenic, E.; Ghogare, R.; Dhingra, A. Biochar—A panacea for agriculture or just carbon? Horticulturae 2020, 6, 37. [Google Scholar] [CrossRef]
  22. Lehmann, J. Bioenergy in the black. Front. Ecol. Environ. 2007, 5, 381–387. [Google Scholar] [CrossRef]
  23. Shen, Z.; Hou, D.; Jin, F.; Shi, J.; Fan, X.; Tsang, D.C.W.; Alessi, D.S. Effect of production temperature on lead removal mechanisms by rice straw biochars. Sci. Total Environ. 2019, 655, 751–758. [Google Scholar] [CrossRef] [PubMed]
  24. Lehmann, J.; Joseph, S. Biochar for environmental management: An introduction. In Biochar for Environmental Management; Routledge: Oxfordshire, UK, 2015; pp. 1–13. [Google Scholar]
  25. Zhao, L.; Cao, X.; Mašek, O.; Zimmerman, A. Heterogeneity of biochar properties as a function of feedstock sources and production temperatures. J. Hazard. Mater. 2013, 256–257, 1–9. [Google Scholar] [CrossRef] [PubMed]
  26. Clough, T.J.; Condron, L.M.; Kammann, C.; Müller, C. A review of biochar and soil nitrogen dynamics. Agronomy 2013, 3, 275–293. [Google Scholar] [CrossRef]
  27. Bruun, E.W.; Ambus, P.; Egsgaard, H.; Hauggaard-Nielsen, H. Effects of slow and fast pyrolysis biochar on soil C and N turnover dynamics. Soil Biol. Biochem. 2012, 46, 73–79. [Google Scholar] [CrossRef]
  28. Castaldi, S.; Riondino, M.; Baronti, S.; Esposito, F.R.; Marzaioli, R.; Rutigliano, F.A.; Vaccari, F.P.; Miglietta, F. Impact of biochar application to a Mediterranean wheat crop on soil microbial activity and greenhouse gas fluxes. Chemosphere 2011, 85, 1464–1471. [Google Scholar] [CrossRef] [PubMed]
  29. Lentz, R.D.; Ippolito, J.A.; Spokas, K.A. Biochar and Manure Effects on Net Nitrogen Mineralization and Greenhouse Gas Emissions from Calcareous Soil under Corn. Soil Sci. Soc. Am. J. 2014, 78, 1641–1655. [Google Scholar] [CrossRef]
  30. Doydora, S.A.; Cabrera, M.L.; Das, K.C.; Gaskin, J.W.; Sonon, L.S.; Miller, W.P. Release of nitrogen and phosphorus from poultry litter amended with acidified biochar. Int. J. Environ. Res. Public Health 2011, 8, 1491–1502. [Google Scholar] [CrossRef] [PubMed]
  31. Burnett, S.E.; Stack, L.B. Survey of the research needs of the potential organic ornamental bedding plant industry in Maine. HortTechnology 2009, 19, 743–747. [Google Scholar] [CrossRef]
  32. USDA. Cecil Series. Official Series Description—CECIL Series. 2007. Available online: https://soilseries.sc.egov.usda.gov/OSD_Docs/C/Cecil.html (accessed on 9 February 2024).
  33. Klute, A. Methods of Soil Analysis; John Wiley & Sons, Inc.: Hoboken, NJ, USA, 2018. [Google Scholar]
  34. Clark, S.; Cavigelli, M. Suitability of composts as potting media for production of organic vegetable transplants. Compost. Sci. Util. 2005, 13, 150–155. [Google Scholar] [CrossRef]
  35. Priha, O.; Smolander, A. Nitrogen transformations in soil under Pinus sylvestris, Picea abies and Betula pendula at two forest sites. Soil Biol. Biochem. 1999, 31, 965–977. [Google Scholar] [CrossRef]
  36. Goh, K.M.; Haynes, R.J. Evaluation of potting media for commercial nursery production of container-grown plants: 1. Physical and chemical characteristics of soil and soilless media and their constituents. N. Z. J. Agric. Res. 1977, 20, 363–370. [Google Scholar] [CrossRef]
  37. Black, C.A.; Evans, D.D.; Ensminger, L.E.; White, J.L.; Clark, F.E. (Eds.) Methods of Soil Analysis; Physical and Mineralogical Properties; American Society of Agronomy: Madison, WI, USA, 1973. [Google Scholar]
  38. Miller, R.O.; Kissel, D.E. Comparison of Soil pH Methods on Soils of North America. Soil Sci. Soc. Am. J. 2010, 74, 310–316. [Google Scholar] [CrossRef]
  39. USEPA. EPA Method 200.8: Determination of Trace Elements in Waters and Wastes by Inductively Coupled Plasma-Mass Spectrometry. 1994. Available online: https://www.epa.gov/esam/epa-method-2008-determination-trace-elements-waters-and-wastes-inductively-coupled-plasma-mass (accessed on 9 February 2024).
  40. USEPA. SW-846 Test Method 3052: Microwave Assisted Acid Digestion of Siliceous and Organically Based Matrices. EPA. 1996. Available online: https://www.epa.gov/hw-sw846/sw-846-test-method-3052-microwave-assisted-acid-digestion-siliceous-and-organically-based (accessed on 9 February 2024).
  41. Kirsten, W.J. Automatic Methods for the Simultaneous Determination of Carbon, Hydrogen, Nitrogen, and Sulfur, and for Sulfur Alone in Organic and Inorganic Materials. Anal. Chem. 1979, 51, 1173–1179. [Google Scholar] [CrossRef]
  42. Kissel, D.E.; Sonon, L. (Eds.) Soil Test Handbook for Georgia; Special Bulletin 62; University of Georgia, College of Agricultural and Environmental Sciences, Agricultural Environmental Services Laboratories: Athens, GA, USA, 2008; Available online: https://aesl.ces.uga.edu/publications/soil/sthandbook.pdf (accessed on 9 February 2024).
  43. Page, A.L. Methods of Soil Analysis. Part 2, Chemical and Microbiological Properties; American Society of Agronomy: Soil Science Society of America: Madison, WI, USA, 1986. [Google Scholar]
  44. Carlson, R.M. Automated Separation and Conductimetric Determination of Ammonia and Dissolved Carbon Dioxide. Anal. Chem. 1978, 50, 1528–1531. [Google Scholar] [CrossRef]
  45. Saha, U.K.; Sonon, L.; Biswas, B.K. A Comparison of Diffusion-Conductimetric and Distillation-Titration Methods in Analyzing Ammonium- and Nitrate-Nitrogen in the KCl-Extracts of Georgia Soils. Commun. Soil Sci. Plant Anal. 2018, 49, 63–75. [Google Scholar] [CrossRef]
  46. Ernst, J.W.; Massey, H.F. The Effects of Several Factors on Volatilization of Ammonia Formed from Urea in the Soil. Soil Sci. Soc. Am. J. 1960, 24, 87–90. [Google Scholar] [CrossRef]
  47. R Core Team. R: A language and Environment for Statistical Computing; R Core Team: Vienna, Austria, 2022. [Google Scholar]
  48. Zhang, A.; Liu, Y.; Pan, G.; Hussain, Q.; Li, L.; Zheng, J.; Zhang, X. Effect of biochar amendment on maize yield and greenhouse gas emissions from a soil organic carbon poor calcareous loamy soil from Central China Plain. Plant Soil 2012, 351, 263–275. [Google Scholar] [CrossRef]
  49. Messiga, A.J.; Hao, X.; Ziadi, N.; Dorais, M. Reducing peat in growing media: Impact on nitrogen content, microbial activity, and CO2 and N2 O emissions. Can. J. Soil Sci. 2020, 102, 77–87. [Google Scholar] [CrossRef]
  50. Lévesque, V.; Jeanne, T.; Dorais, M.; Ziadi, N.; Hogue, R.; Antoun, H. Biochars improve tomato and sweet pepper performance and shift bacterial composition in a peat-based growing medium. Appl. Soil Ecol. 2020, 153, 103579. [Google Scholar] [CrossRef]
  51. El-Naggar, A.; El-Naggar, A.H.; Shaheen, S.M.; Sarkar, B.; Chang, S.X.; Tsang, D.C.W.; Rinklebe, J.; Ok, Y.S. Biochar composition-dependent impacts on soil nutrient release, carbon mineralization, and potential environmental risk: A review. J. Environ. Manag. 2019, 241, 458–467. [Google Scholar] [CrossRef] [PubMed]
  52. Amha, Y.; Bohne, H. Denitrification from the horticultural peats: Effects of pH, nitrogen, carbon, and moisture contents. Biol. Fertil. Soils 2011, 47, 293–302. [Google Scholar] [CrossRef]
  53. Lévesque, V.; Rochette, P.; Ziadi, N.; Dorais, M.; Antoun, H. Mitigation of CO2, CH4 and N2O from a fertigated horticultural growing medium amended with biochars and a compost. Appl. Soil Ecol. 2018, 126, 129–139. [Google Scholar] [CrossRef]
  54. Manirakiza, E.; Ziadi, N.; Luce, M.; Hamel, C.; Antoun, H.; Karam, A. Nitrogen mineralization and microbial biomass carbon and nitrogen in response to co-application of biochar and paper mill biosolids. Appl. Soil Ecol. 2019, 142, 90–98. [Google Scholar] [CrossRef]
  55. Cannavo, P.; Recous, S.; Valé, M.; Bresch, S.; Paillat, L.; Benbrahim, M.; Guénon, R. Organic Fertilization of Growing Media: Response of N Mineralization to Temperature and Moisture. Horticulturae 2022, 8, 152. [Google Scholar] [CrossRef]
  56. Paillat, L.; Cannavo, P.; Barraud, F.; Huché-Thélier, L.; Guénon, R. Growing medium type affects organic fertilizer mineralization and cnps microbial enzyme activities. Agronomy 2020, 10, 1955. [Google Scholar] [CrossRef]
  57. Schomberg, H.H.; Gaskin, J.W.; Harris, K.; Das, K.C.; Novak, J.M.; Busscher, W.J.; Watts, D.W.; Woodroof, R.H.; Lima, I.M.; Ahmedna, M.; et al. Influence of Biochar on Nitrogen Fractions in a Coastal Plain Soil. J. Environ. Qual. 2012, 41, 1087–1095. [Google Scholar] [CrossRef] [PubMed]
Nitrogen 06 00071 g001
Figure 1. Net nitrogen mineralized from control Cecil soil during 102 d incubation (error bars indicate standard deviation).
Figure 1. Net nitrogen mineralized from control Cecil soil during 102 d incubation (error bars indicate standard deviation).
Nitrogen 06 00071 g001
Nitrogen 06 00071 g002
Figure 2. Net nitrogen mineralized from control organic potting media during 102 d incubation (error bars indicate standard deviation).
Figure 2. Net nitrogen mineralized from control organic potting media during 102 d incubation (error bars indicate standard deviation).
Nitrogen 06 00071 g002
Nitrogen 06 00071 g003
Figure 3. Net nitrogen mineralized from pellet mix (A,B) and feather meal (C,D), in Cecil soil and potting media during 102 d incubation (error bars indicate standard deviation).
Figure 3. Net nitrogen mineralized from pellet mix (A,B) and feather meal (C,D), in Cecil soil and potting media during 102 d incubation (error bars indicate standard deviation).
Nitrogen 06 00071 g003
Table 1. Initial characteristics of soil and organic potting media used in the 102 d incubation study.
Table 1. Initial characteristics of soil and organic potting media used in the 102 d incubation study.
SoilTotal CTotal NNH4-NNO3-NPKpH 1CEC70% WHC 2
%mg kg−1 Dry Material mEq 100 g−1g H2O 100 g−1
Cecil1.60.10.124.397.071.15.16.116.0
Organic Potting Media34.90.93.9724.1126.0538.75.3100.6228.0
1. pH measured in 0.01M CaCl2. 2. Water Holding Capacity = WHC.
Table 2. Initial characteristics of materials and fertilizer used in the 102 d incubation study.
Table 2. Initial characteristics of materials and fertilizer used in the 102 d incubation study.
MaterialC:NTotal CTotal NNH4-NNO3-NInorganic N
%mg kg -1 Dry Material
Biochar125.045.00.4165.4-165.4
Feather Meal3.753.114.3967.4-967.4
Pellet Mix3.941.110.61230.057.21287.2
Table 3. Cumulative net Inorganic N mineralized at 102 d from control soil and media at each rate of biochar application.
Table 3. Cumulative net Inorganic N mineralized at 102 d from control soil and media at each rate of biochar application.
Biochar RateCecil SoilPotting Media
mg Inorganic N kg −1 Dry Material (mg Inorganic N g−1 C) 1
0%42.8 (0) a 2190.0 (0) a
5%38.0 (5.9) a−286.9 (17.4) b
10%43.3 (2.8) a−155.5 (7.4) b
1. Values in parenthesis are mg inorganic N g−1 C from biochar at the start of the experiment. 2. Values not followed by a common letter represent significant differences between net inorganic N mineralized at each rate of biochar according to Tukey’s HSD (p < 0.05).
Table 4. Initial carbon and nitrate characteristics of substrates and biochar used in the 102 d study.
Table 4. Initial carbon and nitrate characteristics of substrates and biochar used in the 102 d study.
MaterialTotal CSoluble CNO3-NCO2
mg kg−1 Dry Substrate
Cecil16,00048.024.3-
Organic Potting Media349,000697.8724.1630.1
5% Biochar (added to media)40,179120.5--
10% Biochar (added to media)80,357242.0-1482.0
Table 5. Cumulative net N mineralized (% organic N applied) at 102 d from fertilized soil and media at each rate of biochar application.
Table 5. Cumulative net N mineralized (% organic N applied) at 102 d from fertilized soil and media at each rate of biochar application.
FertilizerBiochar RateCecil SoilPotting Media
% net N min of Organic N Applied (mg Inorganic N kg −1 Dry Soil) 1
Feather Meal0%42.3 (57.8) A b 268.7 (760.0) A a
5%42.1 (57.4) A b66.9 (739.4) A a
10%42.1 (57.5) A a55.7 (616.3) A a
Pellet Mix0%46.5 (60.9) B a57.8 (612.5) A a
5%28.1 (36.8) A b52.4 (555.1) A a
10%45.5 (59.5) AB a51.8 (548.3) A a
1. Values in parenthesis are net N mineralized mg inorganic N kg−1 dry soil. 2. Values not followed by a common uppercase letter represent significant differences between % net N mineralized from each fertilizer by biochar treatment (columns), and different lowercase letters represent significant differences between % net N mineralized between soil and media for each rate of biochar (rows) according to Tukey’s HSD (p < 0.05).
Table 6. Soil pH (calcium chloride 1:4 soil) values of control soils on days 0 and 60, and pH values of fertilized soils on day 60 of incubation study.
Table 6. Soil pH (calcium chloride 1:4 soil) values of control soils on days 0 and 60, and pH values of fertilized soils on day 60 of incubation study.
TreatmentsUnfertilized (Control)Feather MealPellet Mix
MaterialBiochar Rated 0d 60d 60
Cecil0%4.6 a 14.7 a4.3 a4.4 a
Cecil5%6.3 b6.4 b6.2 b6.2 b
Cecil10%6.9 c7.1 c6.9 c6.9 c
Potting Media0%5.2 a5.3 a5.0 a5.0 a
Potting Media5%6.4 b6.4 b6.1 b6.1 b
Potting Media10%6.8 c7.0 c6.9 c6.9 c
1. Values not followed by a common lowercase letter represent significant differences between soil and media pH at each rate of biochar according to Tukey’s HSD (p < 0.01).
Disclaimer/Publisher’s Note: The statements, opinions and data contained in all publications are solely those of the individual author(s) and contributor(s) and not of MDPI and/or the editor(s). MDPI and/or the editor(s) disclaim responsibility for any injury to people or property resulting from any ideas, methods, instructions or products referred to in the content.

Share and Cite

MDPI and ACS Style

Pulliam, J.J.; Cassity-Duffey, K.; Cabrera, M. Effect of Biochar on the Nitrogen Mineralization of Commercial Organic Fertilizers in Both Mineral Soil and Organic Potting Media. Nitrogen 2025, 6, 71. https://doi.org/10.3390/nitrogen6030071

AMA Style

Pulliam JJ, Cassity-Duffey K, Cabrera M. Effect of Biochar on the Nitrogen Mineralization of Commercial Organic Fertilizers in Both Mineral Soil and Organic Potting Media. Nitrogen. 2025; 6(3):71. https://doi.org/10.3390/nitrogen6030071

Chicago/Turabian Style

Pulliam, James Johnathan, Kate Cassity-Duffey, and Miguel Cabrera. 2025. "Effect of Biochar on the Nitrogen Mineralization of Commercial Organic Fertilizers in Both Mineral Soil and Organic Potting Media" Nitrogen 6, no. 3: 71. https://doi.org/10.3390/nitrogen6030071

APA Style

Pulliam, J. J., Cassity-Duffey, K., & Cabrera, M. (2025). Effect of Biochar on the Nitrogen Mineralization of Commercial Organic Fertilizers in Both Mineral Soil and Organic Potting Media. Nitrogen, 6(3), 71. https://doi.org/10.3390/nitrogen6030071

Article Metrics

Back to TopTop