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Cited by 227Soil Carbon and Nitrogen DynamicsAgricultural Science and FertilizationSoil Management and Crop Yield

Biochar improves maize growth by alleviation of nutrient stress in a moderately acidic low-input Nepalese soil

Open access
Pandit, Naba Raj, Mulder, Jan, Hale, Sarah Elizabeth, Martinsen, Vegard, Schmidt, Hans Peter, Cornelissen, Gerard·2018·Science of The Total Environment
DOI 10.1016/j.scitotenv.2018.01.022
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Abstract

We studied the role of biochar in improving soil fertility for maize production. The effects of biochar on the alleviation of three potential physical-chemical soil limitations for maize growth were investigated, i.e. water stress, nutrient stress and acid stress. Experiments involved soils with two dosages of biochar (0.5% and 2% w:w), as well as ones without biochar, in combination with four different dosages of NPK fertilizer, water and lime. Biochar was produced from the invasive shrubby weed Eupatorium adenophorum using flame curtain kilns. This is the first study to alleviate one by one the water stress, nutrient stress and acid stress in order to investigate the mechanisms of biochar effects on soil fertility. Biochar addition increased soil moisture, potassium (K) and plant available phosphorous (P-AL), which all showed significant positive relationship (p<0.001) with above ground biomass of maize. However, biochar was much more effective at abundant soil watering (+311% biomass) than at water-starved conditions (+67% biomass), indicating that biochar did increase soil moisture, but that this was not the main reason for the positive biomass growth effects. Biochar addition did have a stronger effect under nutrient-stressed conditions (+363%) than under abundant nutrient application (+132%). Biochar amendment increased soil pH, but liming and pH had no effect on maize dry biomass, so acidity stress alleviation was not the mechanism of biochar effects on soil fertility. In conclusion, the alleviation of nutrient stress was the probably the main factor contributing to the increased maize biomass production upon biochar addition to this moderately acidic Inceptisol.

AI snapshot

Written from the paper’s full text.

TL;DR

Biochar improved maize growth in a moderately acidic, low-CEC Nepalese silty loam mainly by alleviating nutrient stress, especially through increased K and plant-available P, rather than by relieving water or acid stress. The study falsified its water-stress and acid-stress hypotheses while not falsifying the nutrient-stress hypothesis.

Key findings

  • Biochar (2% w:w) increased soil water retention at field capacity from 29.8 ± 1.8% to 35.3 ± 0.2% and plant available water from 20.8 ± 1.9% to 25.5 ± 0.5%, and raised pH, CEC, exchangeable K⁺, Mg²⁺ and Ca²⁺; P-AL increased from 11.1 mg kg⁻¹ in control to 23.4 and 84.1 mg kg⁻¹ at 0.5% and 2% biochar, respectively.
  • Under nutrient stress (1/3 NPK), biochar increased maize dry biomass from 2.9 ± 1.1 g per pot in control by +120% at 0.5% biochar (6.4 ± 0.7 g per pot) and +231% at 2% biochar (9.6 ± 1.3 g per pot); at the highest NPK rate, increases were +69% and +132%.
  • Under water stress, 2% biochar increased biomass by +67% to +311% depending on watering rate, but the effect was weaker under water-stressed conditions; liming increased pH and Ca/Al but had no significant effect on maize biomass (P = 0.8), while biochar was the only main factor increasing biomass across liming rates.
  • PRS™-measured K⁺ supply increased from 23.6 ± 2.5 to 667 ± 215 at the lowest NPK rate with 2% biochar, and biomass correlated with K⁺ (R² = 0.51, P < 0.001) and P-AL (R² = 0.61, P < 0.001).

Methods

  • Greenhouse pot trial in Matatirtha, Nepal (11 May–5 July 2016) using maize variety Manakamana-4 in 6 L pots with 3 kg air-dried soil; soil was a moderately acidic (pH CaCl₂ 4.5; pH water 5.1), low-CEC (6.05 cmolc kg⁻¹), silty loam Inceptisol from Rasuwa, Nepal. Biochar was produced from *Eupatorium adenophorum* at 600–700 °C and applied at 0, 0.5% (10 t ha⁻¹) and 2% (40 t ha⁻¹).
  • Three separate stress-alleviation experiments manipulated water, NPK fertilizer, or lime at four levels each, with nine treatments per experiment in quadruplicate completely randomized design (n = 4), plus shared full-input treatments.
  • Measurements included soil moisture by TDR, in-situ nutrient supply by PRS™ probes, soil pH, stomatal conductance, maize above-ground biomass at 50 d, and ex-situ CEC, P-AL and plant available water; analysis used two-factor fixed-effect ANOVA with Tukey tests, plus regression and attempted ANCOVA.

Limitations

  • The paper states that the experiment used one soil representative of low-fertility soils, and that maize is more sensitive to drought and nutrient conditions and more tolerant to low pH than other crops, so results may not fully represent other plants; repetition is recommended across soils, biochar types and crop types, and mechanistic field trials are recommended.
  • The study was conducted under controlled greenhouse conditions, excluding external abiotic and biotic disturbances; the authors note this improves mechanistic clarity but may reduce field relevance, and a forthcoming study will report field crop yield data.
  • The paper states that PRS™ data were limited: one-way ANOVA was used because there were insufficient replications/observations for three-factor combinations, and pooling datasets for ANCOVA did not allow precise explanation of explanatory soil variables on biomass; root biomass was not considered because roots were only 2–4% of total biomass and root measurement is less accurate.

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

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Crossref · 10.1016/j.scitotenv.2018.01.022

Cites

Statistics

Nothing to recompute.

Claims the paper makes

0 of 33 cited sources checked · 0 supported · 0 flagged

  • Findingown data

    There was a significant interaction between biochar dosage and watering rate on maize biomass production.

    “A significant interaction between the effect of biochar dosages and watering rates on maize biomass production was observed (Fig. 2a, Table 3a-ii).”
    Quote in the paperNot a substantial claim
  • Findingnone given

    Maize biomass increased with daily watering rate.

    “Also, maize biomass increased with daily watering rate.”
    Quote in the paperNot a substantial claim
  • Findingown data

    Leaf stomatal conductance showed a positive relationship with soil moisture content (R2 = 0.37, P = 0.03).

    “Leaf stomatal conductance showed a positive relationship (R 2 = 0.37, P = 0.03) with soil moisture content (Supplementary Fig. 2a) and dry biomass production (R 2 = 0.51, P = 0.008) (Supplementary Fig. 2b).”
    Quote in the paperNot a substantial claim
  • Findingown data

    Biochar addition increased exchangeable K+.

    “Biochar also increased soil CEC and pH as well as exchangeable K + , Mg 2+ and Ca 2+ (Table 2).”
    Quote in the paperSubstantial claim
  • Findingown data

    At the lowest NPK rate, biochar addition increased K+ supply rates from 23.6 ± 2.5 to 667 ± 215.

    “At the lowest NPK rate, biochar addition strongly increased K + supply rates from 23.6 ± 2.5 to 667 ± 215 and PO 4 3--P from 1.6 ± 0.6 to 5.5 ± 2.0 (Table 4).”
    Quote in the paperSubstantial claim
  • May combine two claims. 30
  • Classified as probably not a substantial claim. 27
  • The quote only partly states this claim. 1

  • May combine two claims.

    Findingown data

    Biochar addition (2%) significantly increased the extractable Ca/Al ratio both without lime (from 11.3 ± 0.9 to 23.7 ± 7.2) and with lime (from 32.2 ± 9.0 to 63.8 ± 18.6).

    “Biochar addition (2% biochar) significantly increased Ca/Al ratio both in the absence (from 11.3 ± 0.9 to 23.7 ± 7.2) and presence of lime (from 32.2 ± 9.0 to 63.8 ± 18.6) (Table 4).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Al3+ concentrations in Table 4 were very low compared to Ca2+ and insignificant compared to fluxes of base nutrients.

    “The Al 3+ data in Table 4 are very low compared to those of Ca 2+ , and insignificant compared to the fluxes of base nutrients.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    P-AL was significantly increased upon mineral nutrient (NPK) addition, and the response was stronger when biochar was added.

    “Furthermore, P-AL (mg kg -1 ) was significantly increased upon mineral nutrient (NPK) addition but the response was stronger when biochar was added (Supplementary Table 2).”
    Quote in the paperSubstantial claim

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

    Findingnone given

    No crowding of plant roots in the pots was observed.

    “No crowding of plant roots in the pots was observed.”
    Quote in the paperNot a substantial claim

  • The quote only partly states this claim.

    Findingown data

    A similar trend of increased biomass with biochar was observed for the second and third NPK additions.

    “A similar trend was observed for the combination of biochar and both the second and third NPK addition (Fig. 2b).”
    Quote in the paperNot a substantial claim

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

    Findingreasoning

    The observed soil organic carbon contents after biochar addition (1.64% and 2.94% for 0.5% and 2% biochar) were close to the values expected from simple addition of soil and biochar carbon (1.70% and 2.75%).

    “Based on a simple addition of the amount of carbon in the soil and that via the biochar amendment (that is the addition of biochar containing 70% C for 0.5% and 2% biochar dosages to the present soil organic carbon (1.35% SOC)), the resulting soil organic carbon contents should have been 1.70% and 2.75%, close to the observed values of 1.64 and 2.94%, respectively (Table 2).”
    Quote in the paperNot a substantial claim

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

    Findingnone given

    Hardly any water drained during the trial from either of the treatment pots.

    “Importantly, hardly any water drained during the trial from either of the treatment pots.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingown data

    The sampled soil used in this experiment was moderately acidic (pH CaCl2 4.5; pH water 5.1), low-CEC (6.05 cmol c kg -1 extracted with 1 M NH 4 NO 3 ), silty loam.

    “The sampled soil used in this experiment was moderately acidic (pH CaCl2 4.5; pH water 5.1), low-CEC (6.05 cmol c kg -1 extracted with 1 M NH 4 NO 3 ), silty loam (Supplementary Table 1).”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Findingown data

    Lime addition increased soil pH and Ca/Al ratio in PRS probes membranes.

    “Lime addition increased soil pH (Fig. 3a) and Ca/Al ratio in the PRS™ probes membranes (Table 4).”
    Quote in the paperNot a substantial claim

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

    Findingcitation

    Stomatal conductance was on the lower end of the range previously observed for maize (<100 mmol m-2 s-1 under drought and 100-200 under fully irrigated), with the same trend of lower stomatal conductance under water stress.

    “Stomatal conductance was on the lower end of the range previously observed for maize b100 mmol m -2 s -1 under drought conditions and 100-200 mmol m -2 s -1 under fully irrigated conditions (Medici et al., 2007), with the same trend of lower stomatal conductance under water stress (Supplementary Fig. 4).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Medici et al., 2007 source

      Not checked in the free run.

  • May combine two claims.

    Findingreasoning

    NUE for N was 10-15% without biochar and 30-45% with biochar.

    “Nutrient use efficiencies (NUE) were improved by biochar addition at all nutrient dosages; NUE for N was 10-15% without biochar and 30-45% with biochar (assuming the same N content of maize biomass (Martinsen et al., 2014) in the presence and absence of biochar).”
    Quote in the paperSubstantial claim
    • The authors state this as an assumption: The N content of maize biomass was the same in the presence and absence of biochar.

  • May combine two claims.

    Findingnone given

    NUEs for P and K were 6-9% and 21-31%, respectively, in absence of biochar, and 18-27% and 60-90%, respectively, in presence of biochar.

    “NUEs for P and K were 6-9% and 21-31%, respectively, in the absence of biochar, and 18-27% and 60-90%, respectively, in the presence of biochar.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation

    Biochar addition increases soil pH, base saturation, nutrient retention capacity and soil CEC, and reduces nutrient leaching.

    “Besides increasing soil pH (higher Ca/Al ratios and higher PO 4 -3 availability) and base saturation (BS) (Glaser et al., 2002;Martinsen et al., 2015) the addition of biochar increases nutrient retention capacity and soil CEC (Chan et al., 2008;Liang et al., 2006) and thus reduces nutrient leaching (Hale et al., 2013;Laird et al., 2010;Martinsen et al., 2014;Steiner et al., 2007).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Glaser et al., 2002 source

      Not checked in the free run.

    • cites Martinsen et al., 2015 source

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    • cites Chan et al., 2008 source

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

    Study design and conductnone given

    Normality and homogenous variances of all data sets were tested with Shapiro-Wilk and Levene's test.

    “Normality and homogenous variances of all data sets were tested with Shapiro-Wilk-and Levene's test.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Premisecitation

    Maize root systems in similar soils in the field constitute only 2-4% of total biomass and weigh only 10-12 g.

    “The plant water status of maize plants growing in 6 l pots is reasonably representative of that in plants growing in field conditions, since maize root systems in similar soils in the field have been found to constitute only 2-4% of total biomass (root-to-shoot-ratios of 0.02-0.04)and the root system weighed only 10-12 g (Abiven et al., 2015).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Abiven et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    In Nepal, soils are often moderately acidic showing low nitrogen, phosphorous and exchangeable base concentrations.

    “In Nepal, soils are often moderately acidic showing low nitrogen (N), phosphorous (P) and exchangeable base concentrations (Brown et al., 1999;Schreier et al., 1994).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Brown et al., 1999 source

      Not checked in the free run.

    • cites Schreier et al., 1994 source

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

    Study design and conductreasoning

    The root systems were not considered in this study because the root constituted only a small portion of total biomass (2-4%) and root biomass determination is often less accurate.

    “Roots systems were not considered in this study as the root constituted only a small portion of total biomass (2-4%), and the determination of root biomass is often less accurate than that of biomass because of incomplete soil/root separation and loss of roots during cleaning.”
    Quote in the paperNot a substantial claim

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

    Interpretationreasoning

    Al3+ was slightly higher in the presence of full NPK (and lime) probably because NPK mineral fertilizer is acidifying.

    “This is probably the reason that Al 3+ , while still low, was slightly higher in the presence of full NPK (and lime; Table 4).”
    Quote in the paperNot a substantial claim

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

    Study design and conductnone given

    Each set of experiments comprised nine treatments with four replications each in completely randomized design (n = 4).

    “Each set of experiments comprised nine treatments with four replications each in completely randomized design (n = 4) resulting in 36 pots per experiment (Table 1).”
    Quote in the paperNot a substantial claim

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

    Premisecitation

    Biochar addition has shown positive effects on soil chemical properties in Nepal, with increased pH, CEC and organic C, and on crop growth.

    “Biochar addition has shown positive effects on soil chemical properties in Nepal, with increased pH, CEC and organic C (Pandit et al., 2017) and crop growth (Schmidt et al., 2015).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites Pandit et al., 2017 source

      Not checked in the free run.

    • cites Schmidt et al., 2015 source

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

    Premisecitation

    Biochar produced from peanut hull at 600 °C reduced leaching of NH4+-N, NO3--N and PO4--P under ex-situ conditions.

    “Biochar produced from peanut hull at 600 °C showed reduced leaching of NH 4 + -N, NO 3 --N and PO 4 --P (35%, 34% and 21%, respectively) under ex-situ conditions (Yao et al., 2012).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Yao et al., 2012 source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation

    Biochar acts as a liming agent and can drastically reduce Al concentration in most degraded soils.

    “The Al concentration can be reduced drastically by addition of biochar that acts as a liming agent in most of the degraded soils (Glaser et al., 2002;Major et al., 2010;Martinsen et al., 2015;Van Zwieten et al., 2010;Yamato et al., 2006).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites Glaser et al., 2002 source

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    • cites Major et al., 2010 source

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    • cites Martinsen et al., 2015 source

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  • May combine two claims.

    Interpretationown data

    The biochar increased biomass yield in ways related to factors other than water stress alleviation, despite increasing soil moisture.

    “These observations indicate that the biochar, despite increasing soil moisture (Fig. 1), increased biomass yield in ways related to factors other than water stress alleviation.”
    Quote in the paperSubstantial claim

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

    Premisecitation

    Biochar addition improves soil water holding capacity and plant available water in loamy and sandy loam soils.

    “With regard to soil physical properties, biochar addition improved soil water holding capacity (WHC) and plant available water (PAW) in both loamy and sandy loam soils (Bruun et al., 2014;Dugan et al., 2010;Martinsen et al., 2014).”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites Bruun et al., 2014 source

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    • cites Dugan et al., 2010

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    • cites Martinsen et al., 2014 source

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

    Study design and conductreasoning

    Pots were rotated every four days until harvest to ensure the homogeneity of the treatments.

    “Pots were rotated every four days until harvest to ensure the homogeneity of the treatments.”
    Quote in the paperNot a substantial claim

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

    Premisecitation

    Jeffery et al. (2017) reported a 25% average crop yield increase in tropical soils upon biochar addition, mostly through liming and nutrient effects.

    “Jeffery et al. (2017) conducted a meta-analysis to investigate these soil constraints, and reported 25% average crop yield increase in tropical soils upon biochar addition, mostly through liming and nutrient effects (N and K retention, P availability and direct K addition).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Jeffery et al., 2017 source

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

    Premisecitation

    Biochar changes the soil surface albedo, which may result in increasing variability in soil moisture.

    “Biochar changes the soil surface albedo (Verheijen et al., 2013), which may result in an increasing variability in soil moisture.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Verheijen et al., 2013 source

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  • May combine two claims.

    Interpretationreasoning

    Biochar probably increased water use efficiency (WUE) and reduced evaporation from the soil surface.

    “Thus, BC probably increased the water use efficiency (WUE), in accordance with earlier observations (Uzoma et al., 2011), and reduced evaporation from the soil surface, which was previously observed for biochar addition (3% w:w) (Basso et al., 2013).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Uzoma et al., 2011 source

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    • cites Basso et al., 2013 source

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  • May combine two claims.

    Interpretationreasoning

    A significant positive relationship between maize biomass production and K supply rates, combined with previous observations that K is the main nutrient added by biochar, indicated that K addition via biochar contributed to alleviation of nutrient stress by biochar.

    “A significant positive relationship between maize biomass production and K supply rates (Supplementary Fig. 4d), combined with previous observations that K is the main nutrient added by the addition of biochar (Martinsen et al., 2014), indicated that the K addition via biochar contributed to the alleviation of nutrient stress by biochar.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites Martinsen et al., 2014 source

      Not checked in the free run.

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

    Interpretationcitation

    In controlled greenhouse conditions with less intense lighting, the albedo effect may be missed, somewhat decreasing study relevance but increasing possibilities to study direct effects of changes in soil chemistry and soil moisture on plant growth.

    “However, in controlled greenhouse conditions with less intense lighting conditions, this effect may be missed (Zhang et al., 2013), somewhat decreasing study relevance but increasing the possibilities to study the direct effects of changes in soil chemistry and soil moisture on plant growth.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Zhang et al., 2013 source

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

    Premisecitation

    Farmers can produce biochar themselves at low cost and labour from Eupatorium shrub using flame curtain pyrolysis kilns.

    “Farmers can produce biochar themselves at low cost and labour from Eupatorium shrub using flame curtain pyrolysis kilns (Schmidt et al., 2015).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Schmidt et al., 2015 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Hypotheses 1 and 3 were falsified with respect to water stress and acid stress respectively, whereas hypothesis 2 was not falsified by the experimental data.

    “Thus, hypotheses 1 and 3 were falsified with respect to water stress and acid stress respectively, whereas hypothesis 2 was not falsified by the experimental data.”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Interpretationnone given

    The experiment was performed for one soil representative of low-fertility soils.

    “The experiment was performed for one soil representative of low-fertility soils.”
    Quote in the paperSubstantial claim

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

    Premisecitation

    Jeffery et al. (2017) showed that biochar addition increased crop yield significantly in low fertility soils, highlighting role of biochar in nutrient stress alleviation.

    “A recent study from Jeffery et al. (2017) showed that biochar addition increased crop yield significantly in low fertility soils, highlighting the role of biochar in nutrient stress alleviation.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Jeffery et al. (2017) source

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

    Interpretationcitation

    Our data are similar to Wang et al. (2016) where biochar addition improved soil moisture but not crop growth.

    “In this respect our data are similar to those of Wang et al. (2016) where biochar addition improved soil moisture but not crop growth.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Wang et al. (2016) source

      Not checked in the free run.

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

    Interpretationreasoning

    As experiments were conducted under controlled greenhouse conditions, any effects related to effect of biochar on pest resistance could probably be ruled out.

    “As the experiments were conducted under controlled greenhouse conditions, any effects related to the effect of biochar on pest resistance could probably be ruled out.”
    Quote in the paperNot a substantial claim

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

    Interpretationreasoning

    We cannot exclude that beneficial biochar effects on soil (micro)biology, including effects on mycorrhizae, may have contributed to observed agronomic effects.

    “We cannot exclude that beneficial biochar effects on soil (micro) biology, including effects on mycorrhizae, may have contributed to the observed agronomic effects.”
    Quote in the paperNot a substantial claim

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

    Interpretationnone given

    This pest can be turned into a resource by making biochar to improve soil fertility.

    “This pest can be turned into a resource by making biochar to improve soil fertility.”
    Quote in the paperNot a substantial claim

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

    Premisecitation

    Herath et al. (2013) reported even stronger increases in PAW (by ~19%) for 10 t ha-1 biochar application on a silty loam soil of Hawera, New Zealand.

    “Even stronger increases in PAW (by ~19%) have been reported for 10 t ha -1 biochar application on a silty loam soil of Hawera, New Zealand (Herath et al., 2013).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Herath et al., 2013 source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning

    Increased nutrient availability (K and P-AL) upon biochar addition showed beneficial effect on maize biomass production in this study, thus, alleviating nutrient stress in silty loam soil of Rasuwa, Nepal.

    “Increased nutrient availability (K and P-AL) upon biochar addition showed beneficial effect on maize biomass production in this study, thus, alleviating nutrient stress in silty loam soil of Rasuwa, Nepal.”
    Quote in the paperSubstantial claim

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

    Premisecitation

    Gautam et al. (2017) reported increased K+ availability upon biochar addition (5 t ha-1) in silty loam Nepalese soil, with main mechanism being high K content in biochar ash and reduced K leaching.

    “A recent study by Gautam et al. (2017) reported increased K + availability upon biochar addition (5 t ha -1 ) in silty loam Nepalese soil, the main mechanism being high content of K in biochar ash as well as reduced K leaching (Laird et al., 2010).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites Gautam et al. (2017) source

      Not checked in the free run.

    • cites Laird et al., 2010 source

      Not checked in the free run.

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

    Premisecitation

    Obia et al. (2016) reported that biochar addition (0.2 and 4% w:w) increased PAW by 3% in Mkushi loamy soils, Zambia.

    “Increased PAW upon 2% biochar addition (from 21% to 26%) (Table 2), was in line with data reported by Obia et al. (2016) where biochar addition (0.2 and 4% w:w) increased PAW by 3% in Mkushi loamy soils (maize field), Zambia.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Obia et al. (2016) source

      Not checked in the free run.

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

    Interpretationnone given

    Maize is more sensitive to drought and nutrient conditions and quite tolerant to low pH conditions than other crops, thus, results found for maize might not be fully representative for other plants.

    “However, maize is more sensitive to drought and nutrient conditions and quite tolerant to low pH conditions than other crops, thus, the results found for maize plant might not be fully representative for other plants.”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data

    Biochar addition in combination with NPK rate had supplementary effects on maize biomass in addition to nutrient retention/addition, probably due to other improved soil physicochemical or biological parameters.

    “Thus, the biochar addition in combination with NPK rate had supplementary effects on maize biomass in addition to nutrient retention/addition -probably due to other improved soil physicochemical or biological parameters.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationreasoning

    The larger amounts of soil moisture in the 2% BC treatment indicate that there was less water loss compared to non-amended soil, despite larger biomass and resulting larger evapotranspiration.

    “The larger amounts of soil moisture in the 2% BC treatment indicate that there was less water loss here compared to non-amended soil, despite the larger biomass and resulting larger evapotranspiration.”
    Quote in the paperSubstantial claim

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

    Premisecitation

    Martinsen et al. (2014) reported an increase of PAW from 18.2% to 22.3% upon biochar addition (10% vol.) in the same soil.

    “Similar trend (an increase of PAW from 18.2% to 22.3%) was reported by Martinsen et al. (2014) upon biochar addition (10% vol.) in the same soil.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites Martinsen et al. (2014) source

      Not checked in the free run.

46 of 46

  • The paper relies on this without support.

    The studied soil is representative for many moderately weathered, eroded and acidified soils of Nepal and beyond.

    “This soil can be considered representative for many moderately weathered, eroded and acidified soils of Nepal and beyond.”

  • The paper relies on this without support.

    There is a knowledge gap regarding to what extent biochar's effect on soil moisture explains its positive effect on crop growth.

    “Although it is apparent that biochar can improve soil moisture, there is a knowledge gap regarding to what extent this effect can explain the positive effect of biochar on crop growth.”

  • The paper relies on this without support.

    There is a knowledge gap regarding the exact mechanism resulting in biochar's positive agronomic effect.

    “Although biochar improves soil quality, there is a knowledge gap regarding the exact mechanism resulting in this positive agronomic effect, as it varies with soil type and the most important soil constraints.”

  • The paper relies on this without support.

    Few studies have explicitly attempted to unravel the soil physical and chemical mechanisms responsible for biochar's positive effect on crop production.

    “However, thus far, few studies have been published where explicit attempts were made to unravel the soil physical and chemical mechanisms responsible for the positive effect of biochar on crop production.”

  • The authors state this as an assumption.

    The amount of water added to the pots was constant for all treatments.

    “In this study, we could assume the amount of water added to the pots to be constant for all the treatments, as there was no water drained during the trial for either of the biochar and non-biochar treatments.”

  • The authors state this as an assumption.

    The N content of maize biomass was the same in the presence and absence of biochar.

    “assuming the same N content of maize biomass (Martinsen et al., 2014) in the presence and absence of biochar”

  • The paper relies on this without support.

    This is the first mechanistic study to investigate the effect of biochar in alleviating water stress, nutrient stress and acid stress by studying parameters one by one under controlled conditions, under maize plantation in a moderately acidic silty loam Nepalese soil.

    “This is the first mechanistic study to investigate the effect of biochar in alleviating some of the most important physical-chemical soil constraints (water stress, nutrient stress and acid stress) by studying the parameters one by one under controlled conditions, under maize plantation in a moderately acidic silty loam Nepalese soil.”
7 of 7

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?

  • Biochar addition to agricultural soils has improved soil water availability, water holding capacity, nutrient availability, increased soil microbial biomass and activity, reduced risk of crust formation and soil erosion, enhanced antibacterial activity, and reduced mobility and toxicity of environmental pollutants.

    “Biochar addition to agricultural soils has improved soil water availability, water holding capacity, and nutrient availability,235, 236, 237 increased soil microbial biomass and activity,238 reduced risk of crust formation and soil erosion,239 enhanced antibacterial activity,240 and reduced mobility and toxicity of environmental pollutants in the soil.241,242”

    From Technologies and perspectives for achieving carbon neutrality (2021) · cites this paper as [237]

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.

  • Full lime dose differs between design and Table 1

    Major

    The experimental-design text gives the highest lime dose as 4.7 g per pot, while Table 1 gives 4.5 g per pot for the shared full-input treatments.

  • PRS nutrient rates are reported per day and per 14 days

    Minor

    The methods and Table 4 report PRS supply rates over a 14-day exposure, but the results describe those rates as per day.

  • Claimed phosphate significance at full NPK conflicts with Table 4

    Minor

    The results say 2% biochar significantly raised phosphate supply at the highest NPK dose. In Table 4, the full-NPK control is marked (a) and the 2%-biochar treatment (ab); their shared letter indicates no significant difference under the table's stated convention.

  • Full NPK dose differs between results and treatment design

    Minor

    The results call the highest NPK addition 1.19 g, whereas the design and Table 1 give the full dose as 1.17 g per pot.

  • Middle soil-pH measurement is dated both day 24 and day 25

    Minor

    The methods say soil pH was measured midway on day 25; the results say the measurements used for the average were taken on day 24.

5 of 5

The citation lists haven’t been fetched yet

References 45 · Cited by 227

Authors
Pandit, N. R., Mulder, J., Hale, S. E., Martinsen, V., Schmidt, H. P., & Cornelissen, G.
Affiliations
  • Norwegian Geotechnical Institute (NO)
  • Norwegian University of Life Sciences (NO)
  • Ithaka Institute for Carbon Strategies (CH)
Corresponding author
Cornelissen, Gerard
ORCID
Venue
Science of The Total Environment
Publisher
Elsevier BV
Published
2018-06
Volume
625
Pages
1380-1389
ISSN
0048-9697 (ISSN-L)
DOI
10.1016/j.scitotenv.2018.01.022
OpenAlex
W2782613841
Cited by
227
References
45
Citations by year
2026: 12 · 2025: 34 · 2024: 32 · 2023: 24 · 2022: 30 · 2021: 32 · 2020: 34 · 2019: 20 · 2018: 9
FWCI
22.21
Type
journal article
Language
en
Open access
Licence
Locations
  • The Science of The Total Environment (publishedVersion, cc-by)
  • PubMed (publishedVersion)
  • NORA - Norwegian Open Research Archives (submittedVersion, other-oa)
  • NORA - Norwegian Open Research Archives (submittedVersion, cc-by-nc-nd)
Funders
The Research Council (217918)
Topics
  • Life Sciences › Agricultural and Biological Sciences › Soil Science › Soil Carbon and Nitrogen Dynamics
  • Life Sciences › Agricultural and Biological Sciences › Soil Science › Agricultural Science and Fertilization
  • Life Sciences › Agricultural and Biological Sciences › Soil Science › Soil Management and Crop Yield
Keywords
biochar, maize growth, nutritional stress, water stress, acid stress, soil fertility, Ageratina adenophora, low-input agriculture, Inceptisol, soil moisture, available phosphorus, potassium, liming, soil pH, biomass production
MeSH terms
Agriculture, Charcoal, Zea mays, Fertilizers, Food, Nepal, Nitrogen, Phosphorus, Soil, Stress, Physiological, Biomass

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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