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Cited by 187Agricultural Science and FertilizationSoil Carbon and Nitrogen DynamicsPlant Growth and Agriculture Techniques

Fourfold increase in pumpkin yield in response to low-dosage root zone application of urine-enhanced biochar to a fertile tropical soil

Open access
Schmidt, Hans, Pandit, Bishnu, Martinsen, Vegard, Cornelissen, Gerard, Conte, Pellegrino, Kammann, Claudia·2015·Agriculture
DOI 10.3390/agriculture5030723
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Abstract

A widely abundant and invasive forest shrub, Eupatorium adenophorum, was pyrolyzed in a cost-efficient flame curtain kiln to produce biochar. The resulting biochar fulfilled all the requirements for premium quality, according to the European Biochar Certificate. The biochar was either applied alone or mixed with fresh cow urine (1:1 volume) to test its capacity to serve as slow release fertilizer in a pumpkin field trial in Nepal. Treatments included cow-manure compost combined with (i) urine-only; (ii) biochar-only or (iii) urine-loaded biochar. All materials were applied directly to the root zone at a biochar dry matter content of 750 kg·ha−1 before seeding. The urine-biochar treatment led to a pumpkin yield of 82.6 t·ha−1, an increase of more than 300% compared with the treatment where only urine was applied, and an 85% increase compared with the biochar-only treatment. This study showed for the first time that a low-dosage root zone application of urine-enhanced biochar led to substantial yield increases in a fertile silt loam soil. This was tentatively explained by the formation of organic coating of inner pore biochar surfaces by the urine impregnation, which improved the capacity of the biochar to capture and exchange plant nutrients.

AI snapshot

Written from the paper’s full text.

TL;DR

A low-dosage root-zone application of urine-enhanced biochar (0.75 t·ha⁻¹ dry matter) produced a fourfold increase in pumpkin yield in a fertile tropical silt loam field trial in Nepal. The authors attribute the effect tentatively to urine impregnation forming an organic coating on biochar pore surfaces that improves nutrient capture and exchange.

Key findings

  • The urine-biochar treatment yielded 82.6 t·ha⁻¹, an increase of more than 300% compared with urine-only and 85% compared with biochar-only.
  • Biochar-only yielded 44.6 t·ha⁻¹ and increased yield by 119% (p = 0.0033) compared with urine-only, which yielded 20.4 t·ha⁻¹.
  • The urine-biochar treatment increased yield by 306% (p < 0.0001) compared with urine-only and by 85% (p < 0.0001) compared with biochar-only.
  • The biochar, made from *Eupatorium adenophorum* by flame curtain pyrolysis, met European Biochar Certificate premium-quality thresholds; at 750 kg·ha⁻¹, nutrient inputs from biochar were negligible except potassium (21 kg·ha⁻¹ K).

Methods

  • Eight on-farm pumpkin field trials were established in Nalang village, Dhading, Nepal, from January to May 2015 on silt loam soils; each trial used randomized blocks with three to five blocks and one pumpkin plant per 3.8 m² plot, totaling 104 plots.
  • Treatments all received 10.5 t·ha⁻¹ cow-manure compost: (A) urine-only, 6.3 m³·ha⁻¹ cow urine; (B) biochar-only, 0.75 t·ha⁻¹ dry-matter biochar; and (C) urine-biochar, 0.75 t·ha⁻¹ dry-matter biochar macerated in 6.3 m³·ha⁻¹ cow urine at roughly 1:1 volume.
  • Biochar was produced from *Eupatorium adenophorum* in a Kon-Tiki flame curtain kiln at 680–700 °C; yield data were analyzed with linear mixed effects models including site-specific random effects, with per-site ANOVA and Tukey tests.

Limitations

  • The paper states that plot size per plant tended to be too small because of strong pumpkin growth, and some shading effects cannot be completely excluded and could have slightly influenced treatment differences.
  • The paper states that the compost was naturally inhomogeneous, so the 4 kg applied per planting pit cannot be considered a representative sample, and plant-available nutrient amounts are only approximations.
  • The paper states that more experiments are needed to prove the biochar–organic–mineral interaction hypothesis and to design safe implementation; it also notes that nutrient leaching, gaseous losses, and immobilization were not measured here.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.3390/agriculture5030723

Cites

77 of 77 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 52 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    The biochar-only treatment caused a significant increase of 119% (p = 0.0033) compared with the urine-only treatment.

    “The biochar-only treatment caused a significant increase of 119% (p = 0.0033) compared with the treatment where only urine was applied”
    Quote in the paperNot a substantial claim
  • Findingown data

    The urine-biochar treatment increased pumpkin yield by 306% (p < 0.0001) compared with the urine-only treatment (~31 vs ~8 kg/plant).

    “an increase of more than 300% compared OPEN ACCESS Agriculture 2015, 5 724 with the treatment where only urine was applied”
    • Also stated in: § 3. Results and Discussion · plain
      “the pumpkin yield increased by 306% (p < 0.0001) in the urine-biochar treatment compared with the treatment where only urine was applied (~31 and ~8 kg•plant -1 , respectively)”
    Quote in the paperSubstantial claim
  • Findingown data

    The total yields as well as the percentage yield increases of the urine-biochar and biochar-only treatments compared with the urine-only treatment varied strongly between the individual sites.

    “The total yields as well as the percentage yield increases of the urine-biochar and biochar-only treatments compared with the urine-only treatment varied strongly between the individual sites”
    Quote in the paperNot a substantial claim
  • Findingown data

    The urine-biochar treatment led to a pumpkin yield of 82.6 t/ha.

    “The urine-biochar treatment led to a pumpkin yield of 82.6 t•ha -1”
    • Also stated in: § 3. Results and Discussion · plain
      “the average yield of 82.6 t•ha -1 that was reached in the urine-biochar treatment even exceeded the expected yield in optimized conventional pumpkin production”
    Quote in the paperSubstantial claim
  • Findingown data

    The cow manure compost had a total nitrogen, phosphate and potassium content of 14 g/kg (DM), 7 g/kg (DM) and 18 g/kg (DM), respectively.

    “The cow manure compost that was used in equal amounts in each plot was well matured and had a total nitrogen, phosphate and potassium content of 14 g•kg -1 (DM), 7 g•kg -1 (DM) and 18 g•kg -1 (DM), respectively.”
    Quote in the paperNot a substantial claim
  • Classified as probably not a substantial claim. 27
  • May combine two claims. 36
  • The quote only partly states this claim. 1

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data

    The biochar had a specific surface area (BET) of 215 m2/g and a specific weight of 120 g/L.

    “With a specific surface area (BET) of 215 m 2 •g -1 and a specific weight of only 120 g•L -1 , this very lightweight, low-density biochar had a high water-holding capacity 6.5 times its own weight.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingreasoning

    The NPK input rate per hectare corresponded to approximately 82:24:115 for the urine-only treatment, 22:22:78 for the biochar-only treatment and 82:24:136 for the urine-biochar treatment.

    “The NPK input rate per hectare corresponded to approximately 82:24:115 for the urine-only treatment, 22:22:78 for the biochar-only treatment and 82:24:136 for the urine-biochar treatment.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The cow urine nutrient contents corresponded to approximately 60 kg/ha TN, 2 kg/ha P2O5, and 58 kg/ha K application rates.

    “corresponding to approximately 60 kg•ha -1 TN, 2 kg•ha -1 P2O5, and 58 kg•ha -1 K application rates”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The biochar had a pH of 9.8, a carbon content of 72% and an H/Corg molar ratio of 0.2.

    “The biochar had a pH of 9.8, a carbon content of 72% and an H/Corg molar ratio of 0.2.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The urine-biochar treatment increased pumpkin yield by 85% (p < 0.0001) compared with the biochar-only treatment (~17 kg/plant).

    “and an 85% increase compared with the biochar-only treatment.”
    • Also stated in: § 3. Results and Discussion · plain
      “and by 85% (p < 0.0001) compared with the biochar-only treatment (~17 kg•plant -1 )”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingreasoning

    At 2.8% (w/w) potassium, the application of 750 kg/ha biochar corresponded to 21 kg/ha potassium.

    “At 2.8% (w/w) potassium, the application of 750 kg•ha -1 biochar corresponded to 21 kg•ha -1 potassium.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The yields in the urine-biochar treatment were consistently significantly higher (p < 0.05) than those in the urine-only treatment and mostly significantly higher (p < 0.05) than the treatments with biochar-only (four out of seven).

    “the yields in the urine-biochar treatment were consistently significantly higher (p < 0.05) than those in the urine-only treatment and mostly significantly higher (p < 0.05) than the treatments with biochar-only (four out of seven).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The amount of plant available N, P2O5 and K applied with the compost was a maximum of 22 kg/ha, 22 kg/ha, and 57 kg/ha, respectively.

    “the amount of plant available N, P2O5 and K applied with the compost was a maximum of 22 kg•ha -1 , 22 kg•ha -1 , and 57 kg•ha -1 , respectively.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data

    The biochar had a high water-holding capacity 6.5 times its own weight.

    “this very lightweight, low-density biochar had a high water-holding capacity 6.5 times its own weight.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The total nitrogen, phosphate and potassium content of the cow urine were 9.5 g/L, 0.35 g/L, and 9.2 g/L, respectively.

    “The total nitrogen (TN), phosphate (P2O5) and potassium (K) content of the cow urine were 9.5 g•L -1 , 0.35 g•L -1 , and 9.2 g•L -1 , respectively”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    No correlation existed between soil pH and yield stimulation among the 8 sites or between the three sites with pH below 5 and those above this value.

    “However, no correlation existed between soil pH and yield stimulation among the 8 sites or between the three sites with pH below 5 and those above this value (Tables 1 and 3).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingcitation

    The average yield in the urine-only treatment was 20.4 t/ha, i.e., at the lower end of conventional farming standards.

    “The average yield in the urine-only treatment was 20.4 t•ha -1 , i.e., at the lower end of conventional farming standards”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The yield of the biochar-only treatment was more than double compared with the urine-only treatment, which had a much closer-to-optimal NPK application quantity and ratio.

    “It is all the more remarkable that the yield of the biochar-only treatment was more than double compared with the urine-only treatment, which had a much closer-to-optimal NPK application quantity and ratio.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingreasoning

    The pumpkin yield increases obtained in the urine-biochar treatments and the harvest results exceeded even those of optimized conventional farming.

    “The pumpkin yield increases obtained in the urine-biochar treatments and the harvest results exceeded even those of optimized conventional farming, demonstrating that organic enhancement of biochar combined with concentrated root zone application can improve plant nutrition and hence crop productivity even at very low dosages of biochar on a per-hectare basis.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing), S4 (based). May combine two claims.

    Findingnone given

    The biochar made from an invasive forest shrub and produced at low cost by farmers themselves using a flame curtain pyrolysis kiln was of excellent quality, qualifying for premium quality of the European Biochar Certificate.

    “The biochar made from an invasive forest shrub and produced at low cost by farmers themselves using a flame curtain pyrolysis kiln was of excellent quality, qualifying for premium quality of the European Biochar Certificate.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    The authors of the meta-analysis concluded that positive changes in crop productivity might only be achieved when biochar application rates exceed 5 t/ha.

    “The authors of the study further concluded that positive changes in crop productivity might only be achieved when biochar application rates exceed 5 t•ha -1 [6].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [6] Lehmann, J., and Joseph, S. (2015). Biochar for Environmental Management, Earthscan. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    The two lead farmers were present during the harvest of each trial and measured the weight of the harvested pumpkins using the same scales for each trial.

    “The two lead farmers were present during the harvest of each trial and measured the weight of the harvested pumpkins using the same scales for each trial.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Interpretationreasoning

    The substantial yield increases were tentatively explained by the formation of organic coating of inner pore biochar surfaces by the urine impregnation, which improved the capacity of the biochar to capture and exchange plant nutrients.

    “This was tentatively explained by the formation of organic coating of inner pore biochar surfaces by the urine impregnation, which improved the capacity of the biochar to capture and exchange plant nutrients.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    In both blending with compost and co-composting, the porous biochar adsorptive surface sites are charged with nutrients, thereby stimulating microbial colonization, improving biochar surface reactivity through accelerated oxidative aging and promoting dissolved organic carbon (DOC) adsorption and coating.

    “In both cases, the porous biochar adsorptive surface sites are charged with nutrients [18,19], thereby stimulating microbial colonization [20], improving biochar surface reactivity through accelerated oxidative aging [21,22] and promoting dissolved organic carbon (DOC) adsorption and coating [18,[23][24][25].”
    Quote in the paperSubstantial claim0 of 5 sources checked
    • cites [18] Prost, 2013, Biochar affected by composting with farmyard manure, J. Environ. Qual. source

      Not checked in the free run.

    • cites [19] Steiner, 2010, Reducing nitrogen loss during poultry litter composting using biochar, J. Environ. Qual. source

      Not checked in the free run.

    • cites [20] Doan, 2014, Influence of buffalo manure, compost, vermicompost and biochar amendments on bacterial and viral communities in soil and adjacent aquatic systems, Appl. Soil Ecol. source

      Not checked in the free run.

    • cites [21] Cheng, 2009, Ageing of black carbon along a temperature gradient, Chemosphere source

      Not checked in the free run.

    • cites [22] Zimmerman, 2010, Abiotic and microbial oxidation of laboratory-produced black carbon (biochar), Environ. Sci. Technol. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Field and pot trial results following the application of biochar-compost blends revealed substantial yield increases and suggested that the total application amount of biochar can be reduced.

    “Field and pot trial results following the application of biochar-compost blends revealed substantial yield increases [26][27][28][29] and suggested that the total application amount of biochar can be reduced.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [26][27][28][29]

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    In Zambia, biochar produced from maize cobs was applied at only 4 t/ha in hoe-dug pits before seeding maize; this increased harvests by up to a factor of four in a weathered acidic sandy soil.

    “In Zambia, biochar produced from maize cobs was applied at only 4 t•ha -1 in hoe-dug pits before seeding maize; this increased harvests by up to a factor of four in a weathered acidic sandy soil [4].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [4] Cornelissen, 2013, Biochar effect on maize yield and soil characteristics in five conservation farming sites in zambia, Agronomy source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductnone given

    Each trial consisted of three, four or five randomized blocks, with each block containing three treatment plots covering an area of 3.8 m2.

    “Each trial consisted of three, four or five randomized blocks, with each block containing three treatment plots covering an area of 3.8 m 2 .”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    A recent meta-analysis of 60 published biochar field trials revealed that the average yield increase in crop production was around 18%.

    “A recent meta-analysis of 60 published biochar field trials [4] revealed that the average yield increase in crop production was around 18%.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [4] Cornelissen, 2013, Biochar effect on maize yield and soil characteristics in five conservation farming sites in zambia, Agronomy source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Premisecitation

    Enhancement of biochar with either organic or mineral nutrients has been suggested to eliminate or counteract the negative effects of applying freshly produced biochars.

    “In order to eliminate or counteract the negative effects of applying freshly produced biochars, the enhancement of biochar with either organic or mineral nutrients has been suggested [13][14][15][16].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [13][14][15][16]

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Subsequent pot trials with the co-composted biochar manually extracted from the compost led to plant growth stimulation of Chenopodium quinoa of 305% versus -61% with untreated biochar compared with the unamended control.

    “Subsequent pot trials with the co-composted biochar manually extracted from the compost led to plant growth stimulation of Chenopodium quinoa of 305% versus -61% with untreated biochar compared with the unamended control.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [12] Kammann, 2015, Plant growth improvement mediated by nitrate capture in co-composted biochar, Sci. Rep. source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductnone given

    All plots were equally irrigated during the first two drier months following local farmer practice.

    “All plots were equally irrigated during the first two drier months following local farmer practice.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Study design and conductnone given

    The plots were hand weeded; no supplemental fertilizer or pesticides were applied until harvest.

    “The plots were hand weeded; no supplemental fertilizer or pesticides were applied until harvest.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    The three biochar meta-analyses available to date exclusively compared the effect of freshly produced biochar with that of the respective control, and did not account for composted or otherwise nutrient-enriched biochars.

    “The three biochar meta-analyses available to date [1,3,4] exclusively compared the effect of freshly produced biochar with that of the respective control, and did not account for composted or otherwise nutrient-enriched biochars.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [1] Abiven, 2013, Heterogeneous global crop yield response to biochar: a meta-regression analysis, Environ. Res. Lett. source

      Not checked in the free run.

    • cites [3] Biederman, 2013, Biochar and its effects on plant productivity and nutrient cycling: A meta-analysis, GCB Bioenergy source

      Not checked in the free run.

    • cites [4] Cornelissen, 2013, Biochar effect on maize yield and soil characteristics in five conservation farming sites in zambia, Agronomy source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    The experiment was laid out with an identical set-up at 8 different field sites.

    “The experiment was laid out with an identical set-up at 8 different field sites, all within a distance of 2 km from the Nalang village.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Blackwell et al. tested banded biochar application on dry land wheat production and concluded that the banding application of biochar at low application rates of 1 t/ha can provide significant positive effects on yield while reducing fertilizer requirements.

    “Blackwell et al. [36] tested banded biochar application on dry land wheat production and concluded that the banding application of biochar at low application rates of 1 t•ha -1 can provide significant positive effects on yield while reducing fertilizer requirements.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [36] Blackwell, 2010, Effect of banded biochar on dryland wheat production and fertiliser use in south-western Australia: An agronomic and economic perspective, Aust. J. Soil Res. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Premisecitation

    Kammann et al. showed that co-composted biochar became highly enriched with nitrate, ammonium, phosphate and DOC, conceivably because of the entrapment of the dissolved nutrients during composting.

    “Kammann et al. [12] showed that co-composted biochar became highly enriched with nitrate, ammonium, phosphate and DOC, conceivably because of the entrapment of the dissolved nutrients during composting.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [12] Kammann, 2015, Plant growth improvement mediated by nitrate capture in co-composted biochar, Sci. Rep. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductnone given

    Two designated lead farmers visited each trial at least once a week to ensure equal treatment.

    “Each farmer maintained the trial during the trial period, while two designated lead farmers (Sita Lamsal and Anisa Kattel) visited each trial at least once a week to ensure equal treatment.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim.

    Premisecitation

    The combination of biochar with compost and also with urine or other nutrient-rich organic liquids has been suggested to produce an effective biochar-based fertilizer.

    “The combination of biochar with compost and also with urine or other nutrient-rich organic liquids has been suggested to produce an effective biochar-based fertilizer [15,30].”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [15] Joseph, 2013, Shifting paradigms: Development of high-efficiency biochar fertilizers based on nano-structures and soluble components, Carbon Manag. source

      Not checked in the free run.

    • cites [30] Schmidt, 2012, Treating liquid manure with biochar, Ithaka J.

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Premisecitation

    The most applied biochar nutrient functionalization process appears to be the blending with compost or a co-composting procedure.

    “The most applied biochar nutrient functionalization process appears to be the blending with compost or a co-composting procedure [16,17].”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [16] Schmidt, 2014, Biochar and biochar-compost as soil amendments to a vineyard soil: Influences on plant growth, nutrient uptake, plant health and grape quality, Agric. Ecosyst. Environ. source

      Not checked in the free run.

    • cites [17] Kumar, S., and Bharti, A. (2012). Management of Organic Waste, In Tech. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The biochar in the Zambian trial was applied fresh from production and was not enhanced with organic nutrients.

    “However, the biochar in the Zambian trial was applied fresh from production and was not enhanced with organic nutrients; it can therefore be assumed that the application rate might be further decreased when the root zone application is performed with nutrient-enhanced biochar slurry [38,39].”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [4] Cornelissen, 2013, Biochar effect on maize yield and soil characteristics in five conservation farming sites in zambia, Agronomy source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    The described and demonstrated methods are not only efficient on weathered and degraded soils in suboptimal agronomic systems but may have the potential to develop into a new, long-term perspective for more sustainable, climate-positive and nutrient efficient agriculture on already fertile soils, particularly in organic farming systems.

    “Contrary to the conclusions in other studies [1,36], the described and demonstrated methods are not only efficient on weathered and degraded soils in suboptimal agronomic systems but may have the potential to develop into a new, long-term perspective for more sustainable, climate-positive and nutrient efficient agriculture on already fertile soils, particularly in organic farming systems.”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [1] Abiven, 2013, Heterogeneous global crop yield response to biochar: a meta-regression analysis, Environ. Res. Lett. source

      Not checked in the free run.

    • cites [36] Blackwell, 2010, Effect of banded biochar on dryland wheat production and fertiliser use in south-western Australia: An agronomic and economic perspective, Aust. J. Soil Res. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    The P2O5 and K inputs are slightly below the fertilizer recommendations but as both nutrients are less mobile than the applied N, a larger part than in the case of N can be taken up by the cultivated plant.

    “The P2O5 and K inputs are slightly below the fertilizer recommendations but as both nutrients are less mobile than the applied N [61][62][63], a larger part than in the case of N can be taken up by the cultivated plant.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [61][62][63]

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation

    It is likely that the biochar mixed with the compost in the root zone captured compost nutrients dissolved during rain events and irrigation, as shown by Kammann et al. and others, thus likely reducing nutrient leaching, gaseous losses and/or immobilization (not measured here).

    “It is likely that the biochar mixed with the compost in the root zone captured compost nutrients dissolved during rain events and irrigation, as shown by Kammann et al. [12] and others [64][65][66][67], thus likely reducing nutrient leaching, gaseous losses and/or immobilization (not measured here).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [12] Kammann, 2015, Plant growth improvement mediated by nitrate capture in co-composted biochar, Sci. Rep. source

      Not checked in the free run.

    • cites [64][65][66][67]

      Not checked in the free run.

  • The quote only partly states this claim.

    Interpretationcitation

    The organic compounds provided by the urine can be adsorbed onto the polyaromatic biochar carbon surfaces by charge assisted hydrogen bonds, water bridging, and Van der Waals interactions.

    “The organic compounds provided by the urine can be adsorbed onto the polyaromatic biochar carbon surfaces by (1) charge assisted hydrogen bonds, (e.g., H-bonds between the electron-rich, proton-acceptors in the urine-contained organic groups and the proton-donors on biochar surface sites, or, vice versa, between the electron-rich biochar aromatic systems and the proton-donors in the organic syste”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [80][81][82]

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    As the trials were not regularly watered by drip irrigation, but irregularly by rain or water buckets, the extra reserve of nearly 2 L of water in the root zone and the compost-nutrient deposit below each pumpkin plant could have resulted in an important difference.

    “As the trials were not regularly watered by drip irrigation, but irregularly by rain or water buckets, the extra reserve of nearly 2 L of water in the root zone and the compost-nutrient deposit below each pumpkin plant could have resulted in an important difference.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation

    The naturally ultra-filtrated ions and organic molecules can penetrate the microporous structure of the biochar and even enter into the nanopore system by water dynamics.

    “The naturally ultra-filtrated ions and organic molecules can penetrate the microporous structure of the biochar and even enter into the nanopore system (as nanopores are mostly larger than the aforementioned average molecular diameter) by water dynamics [79].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [79] Conte, 2015, Water dynamics in different biochar fractions, Magn. Reson. Chem. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S1 (asserted), S3 (load-bearing). May combine two claims.

    Interpretationreasoning

    It is hypothesized that natural variation, field history (terrace construction, erosion, fertilization, preceding crops and crop residues), and influence of agroforestry elements were responsible for the variation in the total yield and yield increases.

    “It is therefore hypothesized that natural variation, field history (terrace construction, erosion, fertilization, preceding crops and crop residues), and influence of agroforestry elements were responsible for the variation in the total yield and yield increases.”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Premisecitation

    Urine contains ions, amino acids, enzymes, serpins, adhesion molecules, hundreds of different small proteins and a multiple of other organic molecules with a maximal molecular diameter of 4.4 nm, as well as cell debris and nuclei.

    “It contains ions, amino acids, enzymes, serpins, adhesion molecules, hundreds of different small proteins and a multiple of other organic molecules with a maximal molecular diameter of 4.4 nm, as well as cell debris and nuclei [78].”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [78] Thongboonkerd, 2002, Proteomic analysis of normal human urinary proteins isolated by acetone precipitation or ultracentrifugation, Kidney Int. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Kammann et al. further proved via repeated KCl extractions that organic plant nutrients captured by biochar remain mostly plant available, which may partially explain the improved nutrient status of the pumpkin plants compared with the non-biochar amended control treatment.

    “Kammann et al. [12] further proved via repeated KCl extractions, that organic plant nutrients captured by biochar remain mostly plant available, which may partially explain the improved nutrient status of the pumpkin plants, compared with the non-biochar amended control treatment.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [12] Kammann, 2015, Plant growth improvement mediated by nitrate capture in co-composted biochar, Sci. Rep. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    Some shading effects cannot completely be excluded and could have slightly influenced the differences between the treatments.

    “Some shading effects, however, cannot completely be excluded and could have slightly influenced the differences between the treatments.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationcitation

    It cannot be ruled out that the biochar delivered more micro-nutrients, but considering that urine and compost both contain all essential micro-nutrients, it is unlikely that the extra micro-nutrients delivered by the biochar would explain the high increase in pumpkin yield compared with the urine-only treatment.

    “It cannot be ruled out that the biochar delivered more micro-nutrients, but considering that urine and compost both contain all essential micro-nutrients [68], it is unlikely that the extra micro-nutrients delivered by the biochar would explain the high increase in pumpkin yield compared with the urine-only treatment.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [68] Provin, 2008, Seasonal dynamics of soil micronutrients in compost-amended bermudagrass turf, Bioresour. Technol. source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Interpretationreasoning

    It is possible that the biochar stimulated the mineralization of the soil and compost nutrients and/or stimulated their uptake by the plants.

    “It is possible that the biochar stimulated the mineralization of the soil and compost nutrients and/or stimulated their uptake by the plants.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Interpretationreasoning

    It cannot be excluded that the rather suboptimal dosages of K and P2O5 were also limiting factors in the urine-only treatment.

    “It can, however, not be excluded that the rather suboptimal dosages of K and P2O5 were also limiting factors in the urine-only treatment.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S4 (based). May combine two claims.

    Interpretationreasoning

    Urine is ultra-filtrated and can thus penetrate even the nanopores of biochar.

    “Naturally, many other liquid organic fertilizers may work as well; however, urine (animal and human) has at least two distinct advantages: (1) it is ultra-filtrated and can thus penetrate even the nanopores of biochar; (2) it is a cheap ubiquitous waste product.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning

    The remaining plant available N in the urine-only treatment was apparently still sufficient to allow consistent growth compared with conventional pumpkin cultivation but was certainly sub-optimal in comparison to the other two treatments.

    “The remaining plant available N was apparently still sufficient to allow consistent growth compared with conventional pumpkin cultivation but was certainly sub-optimal in comparison to the other two treatments.”
    Quote in the paperNot a substantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductreasoning

    Due to the surprisingly strong growth of the pumpkin plants in the urine-biochar treatment, the plot size per plant tended to be too small.

    “Due to the surprisingly strong growth of the pumpkins plants in the urine-biochar treatment, the plot size per plant tended to be too small.”
    Quote in the paperNot a substantial claim
51 of 51

  • The paper relies on this without support.

    No scientific study has yet been undertaken to investigate the fertilizing properties of urine-enriched biochar.

    “However, to the best of our knowledge, no scientific study has yet been undertaken to investigate the fertilizing properties of urine-enriched biochar.”

  • The authors state this as an assumption.

    The application rate of biochar might be further decreased when the root zone application is performed with nutrient-enhanced biochar slurry.

    “it can therefore be assumed that the application rate might be further decreased when the root zone application is performed with nutrient-enhanced biochar slurry [38,39].”

  • The paper relies on this without support.

    Urine is a cheap and ubiquitous waste product.

    “Naturally, many other liquid organic fertilizers may work as well; however, urine (animal and human) has at least two distinct advantages: (1) it is ultra-filtrated and can thus penetrate even the nanopores of biochar; (2) it is a cheap ubiquitous waste product.”
3 of 3

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

Self-check

Percentages, sums and reported differences re-computed from the paper’s own numbers.

Each contradiction between two passages listed here was confirmed by an independent check.

  • Soil pH table does not show half the sites in the stated optimal range

    Minor

    The text defines the optimal pH range as 6 to 6.5, but Table 1 places only Sani Aryal's site within that range, not half of the eight sites.

1 of 1

Cites

Flagged first, then by citations

Research works printed but not linked: 8

  1. Lehmann, J., and Joseph, S. (2015). BIochar for Environmental Management—Science and Technology, Earthscan. [2nd ed.]. · DOI · Paper page
  2. Schmidt, 2012, Treating liquid manure with biochar, Ithaka J., 1, 273
  3. Schmidt, 2012, 55 uses of biochar, Ithaka J., 29, 286
  4. Ladygina, N., and Rineau, F. (2013). A Comparison of Methods to Apply Biochar into Temperate Soils, CRC Press.
  5. Schmidt, 2014, Kon-Tiki flame curtain pyrolysis for the democratization of biochar production, Biochar J., 1, 14
  6. Janick, J., and Whipkey, A. (2007). Issues in New Crops and New Uses, ASHS Press.
  7. Bavec, F., and Bavec, M. (July, January 28). Evaluation of target value of nitrogen fertilizing on the basis soil N min in pumpkins. Proceedings of the Congress of the European Society for Agronomy, Nitra, Slovakia.
  8. Pignatello, 2011, Adsorption of aromatic carboxylate ions to charcoal black carbon is accompanied by release of hydroxide ion, Abstr. Pap. Am. Chem. Soc., 242, 9240

Cited by

Sorted by citations

Related

Authors
Schmidt, H., Pandit, B., Martinsen, V., Cornelissen, G., Conte, P., & Kammann, C.
Affiliations
  • Ithaka Institute for Carbon Strategies (CH)
  • Nepal Agroforestry Foundation (NAF), Kathmandu 44600, Nepal
  • Norwegian University of Life Sciences (NO)
  • Norwegian Geotechnical Institute (NO)
  • University of Palermo (IT)
  • Hochschule Geisenheim University (DE)
Corresponding author
Schmidt, Hans
ORCID
Venue
Agriculture
Publisher
MDPI AG
Published
2015-09-07
Volume
5
Issue
3
Pages
723-741
ISSN
2077-0472 (ISSN-L)
DOI
10.3390/agriculture5030723
OpenAlex
W1549809191
Semantic Scholar
9ad00ec19c3367ba4a93f749dba8c6df66b66af6
Cited by
187
References
77
Citations by year
2026: 8 · 2025: 16 · 2024: 17 · 2023: 18 · 2022: 24 · 2021: 30 · 2020: 13 · 2019: 15 · 2018: 17 · 2017: 21 · 2016: 7
FWCI
20.59
Type
journal article
Language
en
Open access
Licence
Locations
  • Agriculture (publishedVersion, cc-by)
  • RePEc: Research Papers in Economics (submittedVersion)
  • DOAJ (DOAJ: Directory of Open Access Journals) (submittedVersion, cc-by-sa)
  • NORA - Norwegian Open Research Archives (submittedVersion, other-oa)
  • NORA - Norwegian Open Research Archives (submittedVersion, cc-by)
Funders
  • Asian Development Bank
  • Nordic Development Fund
Topics
  • Life Sciences › Agricultural and Biological Sciences › Soil Science › Agricultural Science and Fertilization
  • Life Sciences › Agricultural and Biological Sciences › Soil Science › Soil Carbon and Nitrogen Dynamics
  • Life Sciences › Agricultural and Biological Sciences › Soil Science › Plant Growth and Agriculture Techniques
Keywords
biochar, cow urine, slow-release fertilizer, root zone application, Ageratina adenophora, pyrolysis, cow manure compost, nutrient retention

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-10.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-10.

Statistics and arithmetic are recomputed, not judged.

Confidence bands are shown only for fields calibrated on our annotated test set. None is calibrated yet, so no band is shown.

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