A review on biochar modulated soil condition improvements and nutrient dynamics concerning crop yields: Pathways to climate change mitigation and global food security

In the paper

“When biochar was added to soil, gross N mineralization, recalcitrant nitrogen fraction and labile N fraction were found to be stimulated (Table 3).”

In the paper

“The total P content ranged 16-9500 mg kg -1 for crop residue biochar, 5-6000 mg kg -1 for wood biochar, 29507.40x10 4 mg kg -1 for manure biochar, and 90-23300 mg kg -1 for waste material biochar (Table 3).”

What the sources say

• Not checked yetcites Table 3

In the paper

“| 2 | 1.40 | 35.0 | 74.3 | | 30.9 | | 45.9 |”

In the paper

“| 1 | 0.27 | 0.64 | 0.43 | 0.58 | -0.67 | 0.48 | 0.57 |”

In the paper

“| 1 | 0.27 | 0.64 | 0.43 | 0.58 | -0.67 | 0.48 | 0.57 |”

In the paper

“| 4 | 0.46 | -0.54 | -0.32 | 0.63 | - | - | - |”

In the paper

“| 2 | 1.40 | 35.0 | 74.3 | | 30.9 | | 45.9 |”

In the paper

“| 1 | 0.27 | 0.64 | 0.43 | 0.58 | -0.67 | 0.48 | 0.57 |”

In the paper

“| 3 | 0.51 | 0.48 | -0.65 | -0.29 | 0.74 | 0.37 | 0.56 |”

In the paper

“| 1 | 1.57 | 39.3 | 39.3 | 1.38 | 45.9 | | 45.9 |”

In the paper

“| 4 | 0.46 | -0.54 | -0.32 | 0.63 | - | - | - |”

In the paper

“The first principal component, accounting for 45.9% of the variance in the data”

In the paper

“| 1 | 0.27 | 0.64 | 0.43 | 0.58 | -0.67 | 0.48 | 0.57 |”

In the paper

“| 1 | 1.57 | 39.3 | 39.3 | 1.38 | 45.9 | | 45.9 |”

In the paper

“| 1 | 0.27 | 0.64 | 0.43 | 0.58 | -0.67 | 0.48 | 0.57 |”

In the paper

“| 2 | 0.67 | -0.25 | 0.54 | -0.43 | 0.06 | 0.79 | -0.61 |”

In the paper

“In this case, the total variance explained by the first two principal components was 76.8%.”

In the paper

“| 3 | 0.62 | 15.5 | 89.8 | 0.93 0.70 | 23.2 | 76.8 100 | 45.9 |”

In the paper

“| 2 | 0.67 | -0.25 | 0.54 | -0.43 | 0.06 | 0.79 | -0.61 |”

In the paper

“| 3 | 0.51 | 0.48 | -0.65 | -0.29 | 0.74 | 0.37 | 0.56 |”

In the paper

“| 4 | 0.46 | -0.54 | -0.32 | 0.63 | - | - | - |”

In the paper

“| 1 | 0.27 | 0.64 | 0.43 | 0.58 | -0.67 | 0.48 | 0.57 |”

In the paper

“The latter principal component shows an inverse relationship between [pyrolysis temperature and pH] and [loading rate and CEC].”

In the paper

“| 2 | 0.67 | -0.25 | 0.54 | -0.43 | 0.06 | 0.79 | -0.61 |”

In the paper

“| 3 | 0.51 | 0.48 | -0.65 | -0.29 | 0.74 | 0.37 | 0.56 |”

In the paper

“| 1 | 0.27 | 0.64 | 0.43 | 0.58 | -0.67 | 0.48 | 0.57 |”

In the paper

“| 3 | 0.51 | 0.48 | -0.65 | -0.29 | 0.74 | 0.37 | 0.56 |”

In the paper

“| 2 | 0.67 | -0.25 | 0.54 | -0.43 | 0.06 | 0.79 | -0.61 |”

In the paper

“| 2 | 1.40 | 35.0 | 74.3 | | 30.9 | | 45.9 |”

In the paper

“and was instead dominated by application rate and yield, which display an inverse relationship.”

In the paper

“| 4 | 0.46 | -0.54 | -0.32 | 0.63 | - | - | - |”

In the paper

“and (ii) between biochar loadings and change in CEC of soil.”

In the paper

“| 2 | 0.67 | -0.25 | 0.54 | -0.43 | 0.06 | 0.79 | -0.61 |”

In the paper

“| 2 | 0.67 | -0.25 | 0.54 | -0.43 | 0.06 | 0.79 | -0.61 |”

In the paper

“| 3 | 0.51 | 0.48 | -0.65 | -0.29 | 0.74 | 0.37 | 0.56 |”

In the paper

“| 3 | 0.51 | 0.48 | -0.65 | -0.29 | 0.74 | 0.37 | 0.56 |”

In the paper

“| 2 | 0.67 | -0.25 | 0.54 | -0.43 | 0.06 | 0.79 | -0.61 |”

In the paper

“| 3 | 0.51 | 0.48 | -0.65 | -0.29 | 0.74 | 0.37 | 0.56 |”

In the paper

“and Fe (74800 mg kg -1 ) contents.”

• Also stated in: § ACCEPTED MANUSCRIPT · p. 14 · plain

  “Biochar prepared from swine solids contained 74800, 2240, 4981, 2446 and 27.4 mg kg -1 of Fe, Mn, Zn, Cu, and Mo, respectively (Table 1; Cantrell et al., 2012).”

What the sources say

• Not checked yetcites Cantrell et al., 2012 source

In the paper

“swine solids biochar in Zn (49810 mg kg -1 )”

In the paper

“During pyrolysis, one-third to half of biomass carbon is converted into biochar.”

In the paper

“It also provides other services such as improving soil physical and biological properties (Lehmann andRondon, 2005; Mandal et al., 2016a; Purakayastha et al., 2015; Purakayastha et al., 2016; Bera et al., 2016; Bera et al., 2019).”

What the sources say

• Not checked yetcites Lehmann andRondon, 2005
• Not checked yetcites Mandal et al., 2016a

In the paper

“The very low N content (0.04%) in canola straw biochar conferred it the highest C/N ratio (160:1).”

In the paper

“Poultry litter biochar is a rich in P (3.12%)”

In the paper

“The heat treatment (more often thermochemical treatment) of organic biomass used to produce biochar contributes to its large surface area”

What the sources say

• Not checked yetcites Lehmann et al., 2006 source

In the paper

“Biochar application in soil for increasing crop production and other benefits including soil carbon sequestration is increasingly being recognized as a win-win strategy.”

In the paper

“The N content in many biochar was reported to be more than 4%”

• Also stated in: § ACCEPTED MANUSCRIPT · p. 14 · plain

  “Manure-derived biochar was undoubtedly the richest source of N among all feedstock types of biochar, showing N content as high as 4.45%.”

In the paper

“the Paris Climate Agreement in 2015 set a target for participating countries that 'hold the increase in the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increase to 1.5°C above pre-industrial levels' (IPCC 2015).”

What the sources say

• Not checked yetcites IPCC 2015

In the paper

“while the lowest (0.017%) in yellow pine chip biochar.”

In the paper

“Biochar prepared from swine solids contained 74800, 2240, 4981, 2446 and 27.4 mg kg -1 of Fe, Mn, Zn, Cu, and Mo, respectively (Table 1; Cantrell et al., 2012).”

What the sources say

• Not checked yetcites Cantrell et al., 2012 source

In the paper

“simultaneous actions on negative emissions through sustainable carbon dioxide removal (CDR) technologies and engineered enhancement of natural carbon sinks are also urgently required (Gasser et al. 2015; Rogeljet al., 2016).”

What the sources say

• Not checked yetcites Gasser et al. 2015 source
• Not checked yetcites Rogeljet al., 2016

In the paper

“Data on micronutrient contents in biochar is limited in the literature.”

In the paper

“The global soil has been estimated to hold the largest terrestrial organic carbon pool (~1,500 Pg C to a depth of 1 m; 2,400 Pg C to 2 m depth) (Batjes, 1996).”

What the sources say

• Not checked yetcites Batjes, 1996 source

In the paper

“An increase in organic matter inputs to soil, or a decrease in soil organic matter decomposition rates, or the net carbon gaining effect of the both can increase the carbon stock in soil (Paustian et al., 2016).”

What the sources say

• Not checked yetcites Paustian et al., 2016 source

In the paper

“Waste material biochars had a wide range of C contents (19.2-84.0%) indicating their differential initial constituents.”

In the paper

“The composition of biochar depends upon the nature of feedstock and pyrolysis conditions”

In the paper

“While conventional greenhouse gas emission mitigation strategies, such as lowering the consumption of fossil fuels, are needed to achieve the goal of the Paris Agreement”

In the paper

“In this connection, the application of biochar to soils has been shown to achieve the net carbon gain in soils while also serving for increased plant biomass production by enhancing the nutrient supply to plants and increasing nutrient and water use efficiencies (NUE and WUE) by plants (Kookana et al., 2011; Lehmann et al., 2015; Minasny et al., 2017).”

What the sources say

• Not checked yetcites Kookana et al., 2011 source
• Not checked yetcites Lehmann et al., 2015 source
• Not checked yetcites Minasny et al., 2017 source

In the paper

“The P content was recorded the highest (5.90) in swine solid biochar”

In the paper

“The recently launched '4 per mille Soils for Food Security and Climate' concept also proposes to increase global soil organic matter stocks by 4 per 1000 (or 0.4 %) per year in order to compensate global greenhouse gas emissions due to anthropogenic activities (Minasny et al., 2017).”

What the sources say

• Not checked yetcites Minasny et al., 2017 source

In the paper

“The paper mill biochar (Devi and Saroha, 2015) and poultry manure biochar (Enders et al., 2012) prepared at 600 o C were reported to be rich sources of Ca (25 and 31%, respectively) and Mg (0.87 and 0.29%, respectively) (Table 1).”

What the sources say

• Not checked yetcites Devi and Saroha, 2015
• Not checked yetcites Enders et al., 2012 source

In the paper

“The majority of biochar samples were alkaline in pH with few exceptions such as sugarcane bagasse biochar, yellow pine chip biochar, hazelnut biochar and eucalyptus biochar, which were found to be acidic in solution.”

In the paper

“published literature suggests a wide variation in biochar compositions (Table 1).”

In the paper

“Thus, biochar application to soils has been recommended as an important component of the pathway to 'climate-smart soil' management practices in modern global agriculture (Paustian et al., 2016).”

What the sources say

• Not checked yetcites Paustian et al., 2016 source

In the paper

“The very low N content (0.04%) in canola straw biochar conferred it the highest C/N ratio (160:1).”

In the paper

“Purakayastha et al. (2016) reported that increase in pyrolysis temperature from 400 o C to 600 o C significantly increased the C content, while it decreased the N content in all biochars except that was produced from rice hull.”

What the sources say

• Not checked yetcites Purakayastha et al. (2016) source

In the paper

“These findings were in agreement with the other studies which also found higher C contents in plant material based biochars, e.g., canola, soybean (Yuan et al., 2011), peanut hull, pine chips (Gaskin et al., 2008), Eucalyptus saligna wood and leaf (Singh et al., 2010).”

What the sources say

• Not checked yetcites Yuan et al., 2011
• Not checked yetcites Gaskin et al., 2008
• Not checked yetcites Singh et al., 2010 source

In the paper

“Bayabil et al. (2015) reported that incorporation of woody feedstock (Acacia, Croton, and Eucalyptus) charcoals significantly decreased the soil moisture retention at lower tensions (10 and 30 kPa), resulting in an increase in relative hydraulic conductivity at these tensions in a clay soil.”

What the sources say

• Not checked yetcites Bayabil et al., 2015 source

In the paper

“Biochar may alter soil pH, which in turn can change nutrient solubility, thereby modifying the nutrient availability.”

In the paper

“For example, the C/N ratio of switch grass biochar increased from 54 to 84 when pyrolysis temperature increased from 400 o C to 600 o C (Purakayastha et al., 2016).”

What the sources say

• Not checked yetcites Purakayastha et al., 2016 source

In the paper

“The liming effect of biochar in acid soils, as described above, not only could improve the mineral nutrient supply for plant growth, but also could alleviate Al stress for better crop production (Liu et al. 2013; Dai et al., 2017).”

What the sources say

• Not checked yetcites Liu et al. 2013 source
• Not checked yetcites Dai et al., 2017 source

In the paper

“Contrastingly, Yuan et al. (2011) reported that the C content decreased in corn and peanut biochar with an increasing pyrolysis temperature from 300 o C to 500 o C.”

What the sources say

• Not checked yetcites Yuan et al. (2011)

In the paper

“Alfisols, Ferrosols and Acrisols are inherently highly acidic in nature, and biochar being alkaline material neutralised the acidity.”

In the paper

“The authors also reported that wood chip biochar and waste-water sludge biochar were more efficient in increasing the porosities of the products over straw biochar, and hence showed greater effects on soil macroaggregates (Yu et al., 2016).”

What the sources say

• Not checked yetcites Yu et al., 2016

In the paper

“In contrast, Novak et al. (2009) reported that the C/N of sugarcane bagasse biochar decreased from 129 to 79 when pyrolysis temperature increased from 250 o C to 500 o C.”

What the sources say

• Not checked yetcites Novak et al. (2009) source

In the paper

“Biochar amendments were reported to improve soil bulk density, porosity, water retention, and hydraulic conductivity (Abel et al., 2013; Asai et al., 2009; Atkinson et al., 2010; Jeffery et al., 2011; Karhu et al., 2011; Laird et al., 2010a).”

What the sources say

• Not checked yetcites Abel et al., 2013 source
• Not checked yetcites Asai et al., 2009 source
• Not checked yetcites Atkinson et al., 2010 source

In the paper

“The slow and fast pyrolysis process during heating could also influence the C and N contents, and C/N ratios.”

In the paper

“Thus, maize biochar was reported to accelerate soil N transformations by increasing the net N mineralization (Nelissen et al., 2012, Gundale and DeLuca, 2006), accelerating nitrification (Song et al., 2013), affecting denitrification (Cayuela et al., 2013), reducing ammonia volatilization (Mandal et al., 2016b; 2018), and through adsorption of ammonia”

What the sources say

• Not checked yetcites Nelissen et al., 2012
• Not checked yetcites Gundale and DeLuca, 2006
• Not checked yetcites Song et al., 2013

In the paper

“The impact of peanut hull biochar was more pronounced than pine chip biochar due to the higher contents of K, Ca and Mg in the former, and in the first year of biochar application than the second year (Gaskin et al., 2010).”

What the sources say

• Not checked yetcites Gaskin et al., 2010 source

In the paper

“For instance, PyOM derived from rye grass pyrolyzed at 450 o C induced a strongly positive priming effect within the first 18 days, and thereafter exhibiting a negative priming effect in a forest Cambisol (Maestrini et al., 2014).”

What the sources say

• Not checked yetcites Maestrini et al., 2014 source

In the paper

“Compared to the unamended soil, amendment with biochar (produced at 200 o C and 400 o C from oak wood feedstock) significantly increased N2O emissions, but biochar produced at a higher temperature (600 o C) did not show such effect on N2O emissions (Zhang et al., 2015).”

What the sources say

• Not checked yetcites Zhang et al., 2015 source

In the paper

“These are all indirect evidences of enriched nutrient availabilities resulted from biochar addition to soils.”

In the paper

“During the pyrolysis process, N in biomasses get converted to recalcitrant heterocyclic aromatic structures in biochar, and these structural changes may lead to a reduction in C and N mineralization rates (Chen et al., 2014).”

What the sources say

• Not checked yetcites Chen et al., 2014 source

In the paper

“Therefore, the C stability of leguminous green manure like Ipomoea sp. could be enhanced by converting the raw material into biochar, but the charring process might limit the immediate supply of N.”

In the paper

“This could be due to the biochar induced incresae of soil porosity/aeration that stimulates the aerobic/heterotrophic microbial population resulting in the degradation of recalcitrant SOM in the presence of biochar (Anderson et al., 2011).”

What the sources say

• Not checked yetcites Anderson et al., 2011 source

In the paper

“This showed a direct evidence that PyOM produced at a low temperature could be easily degraded, and its N would become available to plants (Rosa and Knicker, 2011).”

What the sources say

• Not checked yetcites Rosa and Knicker, 2011

In the paper

“The increase in CEC could affect the retention of phosphate by biochar through anion exchange reaction.”

In the paper

“The other important mechanisms include an enhanced abundance of ammonia oxidizing microorganisms (Song et al., 2013), and promotion of denitrification by the transfer of electrons to soil denitrifying microbes (Cayuela et al., 2013).”

What the sources say

• Not checked yetcites Song et al., 2013
• Not checked yetcites Cayuela et al., 2013

In the paper

“As such, soil amended with biochar produced at temperatures exceeding 400°C demonstrated a 25% decrease in dry shoot biomass of water soinach ( Ipomoea aquatica ) compared with unamended soil principally due to N limitation (Chen et al., 2014).”

What the sources say

• Not checked yetcites Chen et al., 2014 source

In the paper

“Biochar being rich in surface functional groups, including aromatic moieties, can alter cation and anion exchange capacities of soils, which further influences N retention (Clough et al., 2013; Slavich et al., 2013; Mandal et al., 2018).”

What the sources say

• Not checked yetcites Clough et al., 2013 source
• Not checked yetcites Slavich et al., 2013 source
• Not checked yetcites Mandal et al., 2018 source

In the paper

“Most of the mineralized NH4 + under biochar treatments came from the recalcitrant N in soil, while in the control soil most mineralized NH4 + originated from the labile N (Nelissen et al., 2012).”

What the sources say

• Not checked yetcites Nelissen et al., 2012

In the paper

“Results showed accelerated soil N cycling following biochar addition, with increased gross N mineralization (185-221%), nitrification (10-69%) and ammonium (NH4 + ) consumption rates (333-508%) (Nelissen et al., 2012).”

What the sources say

• Not checked yetcites Nelissen et al., 2012

In the paper

“The adsorbed NH 4 + -N eventually become available to plants or microbes in the long run reducing the loss of mineral N in soils (Taghizadeh-Toosi et al., 2012a, 2012b).”

What the sources say

• Not checked yetcites Taghizadeh-Toosi et al., 2012a
• Not checked yetcites Taghizadeh-Toosi et al., 2012b

In the paper

“For example, Zhang et al. (2016) studied biochars prepared from 9 different residues, and concluded that the Bladygrass ( Imperata cylindrical ) biochar had the greatest amount of extractable P among all the biochars.”

What the sources say

• Not checked yetcites Zhang et al., 2016

In the paper

“Soil and biochar mixtures showed evidence of both soil nutrient sorption by biochar, and biochar nutrient sorption by the soil, depending upon the biochar and soil types (Mukherjee and Zimmerman, 2013; Rens et al., 2018).”

What the sources say

• Not checked yetcites Mukherjee and Zimmerman, 2013
• Not checked yetcites Rens et al., 2018 source

In the paper

“The extractable P not only depends on the pyrolysis temperature, but also on the feedstock.”

In the paper

“The primary reason for the higher BNF with biochar additions was the greater B and Mo availability in the amended soil than the unamended control, while a greater K, Ca, and P availability with higher soil pH and lower N availability and Al saturation might have also concurrently occurred (Rondon et al., 2007).”

What the sources say

• Not checked yetcites Rondon et al., 2007 source

In the paper

“The NH4 + adsorption capacities of commercial coconut shell activated carbon prepared at 600 o C and 400 o C were found to be 2400 and 600 to 1800 mg NH3 kg -1 carbon, respectively (Rodrigues et al., 2007).”

What the sources say

• Not checked yetcites Rodrigues et al., 2007 source

In the paper

“The available N content increased in an alkaline sandy loam soil too under the influence of biochar, and the effect was more pronounced for maize stover than wheat straw biochar (Purakayastha et al., 2015).”

What the sources say

• Not checked yetcites Purakayastha et al., 2015 source

In the paper

“Recently Hea et al. (2018) reported that biochar application to soil with urea increased NH3 volatilization losses by 14.1% in the first rice season, primarily due to increased pH and concentrations of NH4 + -N in the floodwater, and decreased NH3 losses in the second rice growth season by 6.8%, probably due to its high adsorption capacity for NH4 + and increased nitrification.”

What the sources say

• Not checked yetcites Hea et al., 2018 source

In the paper

“Similarly, biochar addition showed limited effects on the turnover of soil organic carbon, DON and no long-term effect on N mineralization, NH3 volatilization, denitrification and NH4 sorption (Clough et al., 2013).”

What the sources say

• Not checked yetcites Clough et al., 2013 source

In the paper

“Yao et al. (2012) reported that sugarcane bagasse, peanut hull, Brazilian pepperwood, and bamboo biochars could adsorb 112% NH4 + -N from aqueous solution, and Brazilian pepperwood gave the most effective biochar for NH4 + adsorption among these feedstocks.”

What the sources say

• Not checked yetcites Yao et al., 2012 source

In the paper

“However, Macdonald et al. (2014) reported that both poultry litter and wheat straw biochars applied at the rate of 5 and 10 Mg ha -1 did not affect the Olsen's P in an acidic Ferrasol and alkaline Calcisol, but could increase Olsen's P in an acidic aerosol and neutral Vertisol.”

What the sources say

• Not checked yetcites Macdonald et al., 2014 source

In the paper

“Biochar itself is a huge source of K, and it can directly take part in the retention of K in the soil because of having a high CEC (Table 3).”

In the paper

“At higher application rates, P concentrations decreased, which coincided with an increase of soil pH by 0.3-0.7 units (Parvage et al., 2013).”

What the sources say

• Not checked yetcites Parvage et al., 2013 source

In the paper

“Biochar's effect on both soil Olsen-P and microbial biomass-P was increased by higher biochar application rates ensuring lower P-sorption capacity.”

In the paper

“Biochar having high ion exchange capacity might alter P availability by enhancing the anion exchange capacity or by influencing the activity of cations that interact with P (Liang et al., 2006).”

What the sources say

• Not checked yetcites Liang et al., 2006 source

In the paper

“Rice straw biochar with the higher CEC and the lowest contents of Ca 2+ and Mg 2+ showed the greatest inhibition of phosphate adsorption, and thus, could likely be the best choice as an amendment to mobilize phosphate in variably-charged soils (Jiang et al., 2015).”

What the sources say

• Not checked yetcites Jiang et al., 2015 source

In the paper

“Incorporation of the biochars increased the pH of the amended soils, thereby further mobilizing phosphate in the soil (Jiang et al., 2015).”

What the sources say

• Not checked yetcites Jiang et al., 2015 source

In the paper

“The addition of fresh Miscanthus or Salix biochar to soil significantly increased soil P contents, but artificially weathered biochars made no such change in sandy loam soil of the Rothamsted Research experimental farm, United Kingdom (Prendergast-Miller et al., 2014).”

What the sources say

• Not checked yetcites Prendergast-Miller et al., 2014 source

In the paper

“In sandy soil, addition of biochar produced from mixture of Norway spruce ( Picea abies (L.) H. Karst) and Scots pine ( Pinus sylvestris L.) had low P sorption affinity, and thus did not increase the sorption of P in incubated soils (Sonnie et al., 2014).”

What the sources say

• Not checked yetcites Sonnie et al., 2014

In the paper

“These increases were accompnied with an subsequent increase in soil microbial biomass P from 1 to 9 mg kg -1 in the Red earth, and from 9 to 21 mg kg -1 in the Fluvoaquic soil (Zhai et al., 2015).”

What the sources say

• Not checked yetcites Zhai et al., 2015 source

In the paper

“The maximum concentration of water-soluble P was achieved at the rate of 1% wheat residue biochar (w/w) addition to soils with different textural classes, varying the water-soluble P concentrations from 11 to 253% (Parvage et al., 2013).”

What the sources say

• Not checked yetcites Parvage et al., 2013 source

In the paper

“Haefelea et al. (2011) reported that the application of carbonized rice husk biochar increased available P in rice growing soil of International Rice Research Institute (IRRI), Philippines, in the first year, while after three years it did not influence the available P content.”

What the sources say

• Not checked yetcites Haefelea et al., 2011 source

In the paper

“The increased soil microbial activity and reduced soil acidity or increased CEC may be accounted for enhanced P transformation in the soil.”

In the paper

“The wheat residue biochar can act as a source of soluble P, and low and high additions of biochar showed different effects on soil solution P concentration due to possible reactions of P with Ca and Mg added with biochar.”

In the paper

“The lowest N-leaching-loss were observed with BSRFs, and the phenomenon was attributed to the fact that BSRFs had better slow-release characteristics and water holding capacity than normal biochar (Gonzalez et al., 2015; Wen et al., 2017).”

What the sources say

• Not checked yetcites Gonzalez et al., 2015 source
• Not checked yetcites Wen et al., 2017 source

In the paper

“Biochar prepared from Eucalyptus tree either via traditional kiln process at 350°C or by flash carbonization at 800°C significantly increased the soluble Mn concentration (1.39-4.61 mg L -1 ) in an Oxisol relative to the control (1.12 mg L -1 ), while they decreased the plant tissue Mn concentration (0.08-0.17 g kg -1 ) compared to the control (0.41 g kg -1 ) (Butnan et al., 2015).”

What the sources say

• Not checked yetcites Butnan et al., 2015 source

In the paper

“Pyrolytic conversion of biomass into biochar has shown an effective impact on reducing nutrient losses (NH3 volatilization, N2O emission, CO2 emission, NO3 leaching, etc.) from soils, and previous studies found that biochar itself contains nutrients, which help to improve plant growth.”

In the paper

“Some biochars triggered improved growth with increasing pyrolysis temperatures, though opposite trend was also found (Rajkovich et al., 2012).”

What the sources say

• Not checked yetcites Rajkovich et al., 2012 source

In the paper

“Except for the larger application rate (7%), biochar made from corn stover, oak, and pine wood and animal manures exhibited either positive or neutral effect on crop growth, whereas biochar from hazelnut shells did not affect the growth (Enders et al., 2012).”

What the sources say

• Not checked yetcites Enders et al., 2012 source

In the paper

“However, on the same occasion, the total biomass of spring barley ( Hordeum vulgare ) was increased by 11% due to biochar application, though with a non-significant response for grain yield.”

What the sources say

• Not checked yetcites Sun et al., 2014 source

In the paper

“Yao et al. (2011) also found that the phosphate-laden biochar contained valuable nutrients that could act as a slow release fertilizer to enhance soil fertility and sequester C for a longer time in soil.”

What the sources say

• Not checked yetcites Yao et al., 2011 source

In the paper

“Kim et al. (2014) observed that lignocellulosic biomass-derived biochar contained low plant nutrients but could be impregnated with additional nutrients and subsequently pelletized, and the final product could control the release of nutrients at a slower rate resulting in a reduced nutrient loss.”

What the sources say

• Not checked yetcites Kim et al., 2014 source

In the paper

“Among the micronutrients, soil extractable Mn and Fe decreased, while Cu and Zn increased due to the application of a mixed wood biochar (Rogovska et al., 2014).”

What the sources say

• Not checked yetcites Rogovska et al., 2014 source

In the paper

“Similarly, Borchard et al. (2012) reported that composted charcoal could potentially improve plant available Cu 2+ in an acidic sandy soil with small organic matter content.”

What the sources say

• Not checked yetcites Borchard et al., 2012 source

In the paper

“Across all biochar types, average total biomass production of corn ( Zea mays L.) was at par for the application rates of 0.2%, 0.5%, and 2%, but reduced to a minimum at the rate of 7% (Rajkovich et al., 2012).”

What the sources say

• Not checked yetcites Rajkovich et al., 2012 source

In the paper

“However, not only the biochar or soil type, crop choices also can determine the response of biochar as van Zwieten et al. (2010) found that wheat biomass increased linearly up to an biochar application rate of 10 t ha -1 , and decreased with 20 and 50 t ha -1 , whereas radish growth did not decrease with high rate of biochar in an acid soil of the tropics.”

What the sources say

• Not checked yetcites van Zwieten et al., 2010 source

In the paper

“Slow pyrolysis biochar (550 o C) failed to show any effect on exchangeable Ca content after harvest of a maize crop when applied at the rate of 15.0 g kg -1 in a silty Fluvisol, but it became more efficient when the application rate was increased to 100 g kg -1 (Borchard et al., 2014).”

What the sources say

• Not checked yetcites Borchard et al., 2014 source

In the paper

“The BSRFs were also capable of releasing N fertilizer slowly with extended N-longevity, and were more effective in improving total N use efficiency and facilitated cotton plant growth through reducing N loss and improving N retention (Wen et al., 2017).”

What the sources say

• Not checked yetcites Wen et al., 2017 source

In the paper

“Peanut straw biochar pyrolyzed at 400 o C showed significantly higher water soluble Ca and Mg contents in an Oxisol than other starw derived biochars, and rice straw biochar showed the lowest values among various crop straw biochars (Jiang et al., 2015).”

What the sources say

• Not checked yetcites Jiang et al., 2015 source

In the paper

“After biochar application, Ca and Mg limiting Savana Oxisol was higly productive due to 77-320% greater Ca and Mg availability, increasing soil pH and decreasing exchangable acidity (Major et al., 2010).”

What the sources say

• Not checked yetcites Major et al., 2010 source

In the paper

“Studies have shown that biochar based slow-release fertilizers with their effective nutrient retention properties can be widely used in sustainable modern agriculture.”

In the paper

“Pyrolysis temperature was also found to be the most influential parameter for obtaining specific characteristics of rapeseed stem biochar, demonstrating a positive relationship of temperature with pH, microporous structure, surface area, fixed C and ash content, whilst showing a negative relationship with material yield, average pore size, functional groups, volatile matter, O”

What the sources say

• Not checked yetcites Zhao et al., 2018 source

In the paper

“However, Gaskin et al., (2009) found that peanut hull biochar and pine chip biochar failed to show their marks towards crop productivity, and grain yield even decreased for maize crop.”

What the sources say

• Not checked yetcites Gaskin et al., 2009

In the paper

“Application of 0, 8 and 20 t ha -1 of biochar to a Colombian savanna Oxisol continuously for four years (2003-2006) under a maize-soybean rotation reported that the maize grain yield did not increase in the very first year, but increased in the 20 Mg ha -1 plots over the control by 28, 30 and 140%, respectively, in the subsequent years (Major et al., 2010).”

What the sources say

• Not checked yetcites Major et al., 2010 source

In the paper

“Similarly, applying N fertilizer proved beneficial to rice grain yield when 4.0 and 8.0 Mg ha -1 rates of two commercial biochars prepared from wood feedstocks (e.g., teak ( Tectona grandis L.) and rosewood ( Pterocarpus macrocarpus Kurz)) were applied in a study reported from northern Laos, but at higher dose of biochar (16 Mg ha -1 ) with N-fertilizer no positive”

What the sources say

• Not checked yetcites Asai et al., 2009 source

In the paper

“Moreover, no difference between the two biochar treatments were identified, suggesting that even the very high biochar application rate promoted plant growth with a non-detrimental effect (Vaccari et al., 2011).”

What the sources say

• Not checked yetcites Vaccari et al., 2011 source

In the paper

“In contrast to biochar amendment, N fertilizer proved less effective for improving soil quality, but more effective for increasing the rice yield (Huang et al., 2013).”

What the sources say

• Not checked yetcites Huang et al., 2013 source

In the paper

“Another investigation dealing with large volume application of biochar (30 and 60 Mg ha -1 ) on durum wheat in the Mediterranean climate showed positive effects (up to 30%) on biomass production and yield, with no significant differences in the nitrogen content of grains (Vaccari et al., 2011).”

What the sources say

• Not checked yetcites Vaccari et al., 2011 source

In the paper

“Contrary to this observation, Zhang et al., (2012) found maize yield increased by 15.8% and 7.3% without N fertilization, and by 8.8% and 12.1% with N fertilization under biochar amendment at 20 and 40 Mg ha -1 , respectively, in a calcareous flavor-aquic loamy soil.”

What the sources say

• Not checked yetcites Zhang et al., 2012 source

In the paper

“Recently, Ain et al. (2016) reported that application of biochar prepared from a weed ( Parthenium hysterophorus L.) at 370- 417 o C temperature to a rice-wheat cropping system could cut down the cost of fertilizer to half although the yield obtained was just as good as with full application of recommended dose of fertilizers.”

What the sources say

• Not checked yetcites Ain et al., 2016 source

In the paper

“Application of biochar poultry manure compost and pyroligneous solution to a salt-affected soil for consecutive two years showed an ameliorative effect, decreasing the salinity and pH, and subsequently reflected in increased yield of wheat in a tune of 38% (Lashari et al., 2013).”

What the sources say

• Not checked yetcites Lashari et al., 2013 source

In the paper

“Moreover, this treatment was found to be superior for obtaining benefits related to straw reutilization like crop residue incorporation (CRI) and crop residue burning (CRB) in the open field.”

What the sources say

• Not checked yetcites Purakayastha, 2010

In the paper

“Improvement in soil physical properties along with pH, organic carbon and content of exchangeable cations were the reasons suggested for the higher radish yield.”

In the paper

“In another study, the application of rice straw biochar (prepared at 400 °C) at the rate of 2.25 g kg -1 (equivalent to 5.0 t ha -1 ) along with 100% NPK increased the rice yield by 24.3% in an Inceptisol, and by 31.3% in an Alfisol (Bera, 2014).”

What the sources say

• Not checked yetcites Bera, 2014

In the paper

“The bioavailability of N in a wheat-straw biochar prepared at 400 o C was reported to be very low, and did not increase growth of rice crop or nitrogen use efficiency from fertilizer sources during the first year after application (Xie et al., 2013).”

What the sources say

• Not checked yetcites Xie et al., 2013 source

In the paper

“Biochar additions significantly increased total biomass production by 39% at a defined biochar dose of 60 g kg -1 , but decreased biomass at par with the control with a higher biochar dose (90 g kg -1 ).”

What the sources say

• Not checked yetcites Güereña et al., 2015 source

In the paper

“Biochar was added to an agricultural field at three different doses (0, 25 and 50 t ha -1 ) and planted with maize (1 st year) and grass (2 nd and 3 rd years) in an acidic sandy loam soil where the biochar addition affected plant performance in the grass crop with significant increase in foliar N (2 nd year) and aboveground biomass (3 rd year), but biochar treatment behaved neutral”

What the sources say

• Not checked yetcites Jones et al., 2012 source

In the paper

“Rice yield was increased under biochar treatment in an acidic Anthrosol, and such increase was eventually more (9-28%) in the second cycle than in the first cycle (9-12%) of the crop (Zhang et al., 2012).”

What the sources say

• Not checked yetcites Zhang et al., 2012 source

In the paper

“Farrell et al. (2014) reported no significant effect on wheat yield at a low application rate (<1.0 Mg ha -1 ) of biochar in highly P-constrained calcareous soil, but a prominent effect of both biochar and fertilizer on P fractionation was observed.”

What the sources say

• Not checked yetcites Farrell et al., 2014 source

In the paper

“The plant biomass was significantly lower at higher biochar application rates (5 and 10 t ha -1 ), having a prominent impact on shoot production but also evident in grain yield and root biomass (Macdonald et al., 2014).”

What the sources say

• Not checked yetcites Macdonald et al., 2014 source

In the paper

“More interestingly, the same study further hinted that biochar amendment showed an additional benefit on rice yield under N fertilizer application, and there was a close relationship between the effect of biochar amendment on rice yield and agronomic N use efficiency.”

What the sources say

• Not checked yetcites Huang et al., 2013 source

In the paper

“In acidic sandy soils, the application of rice hull biochar (2% rate) prepared at 350-400 o C increased sugarcane yield in Florida, USA, probably because biochar modulated the nutrient enrichment in the soil (Alvarez-Campos et al., 2018).”

What the sources say

• Not checked yetcites Alvarez-Campos et al., 2018

In the paper

“Fertilizer application along with carbonized rice husk (CRH-biochar) improved the grain yields of rice, but the improvement was not always significant and even showed a decline in yield at Nitisol of Siniloan, Philippines (Haefele et al., 2011).”

What the sources say

• Not checked yetcites Haefele et al., 2011

In the paper

“Only in a gleyic Acrisols, the application of CRH-biochar resulted in a higher yield of rice in all four seasons, although the significant increase was only observed in the third and fourth wet seasons (Haefele et al., 2011).”

What the sources say

• Not checked yetcites Haefele et al., 2011

In the paper

“The mechanism through which the positive impacts of biochars on P and K is not clear yet.”

In the paper

“and mostly that could be somewhat complemented by application of fertilizers along with biochar.”

In the paper

“Such responses confirmed earlier results with moong bean [ Vigna radiata (L.) R. Wilczek], soybean [ Glycine max (L.) Merr.], and pea ( Pisum sativum L.) (Iswaran et al., 1980), or with cowpea ( Vigna unguiculata L.) and rice ( Oryza sativa L.) (Nehls, 2002; Lehmann et al., 2003).”

What the sources say

• Not checked yetcites Iswaran et al., 1980 source
• Not checked yetcites Nehls, 2002
• Not checked yetcites Lehmann et al., 2003 source

In the paper

“However, at a higher rate, biochar might decrease the yield of crops”

In the paper

“However, biochar produced from manure sources being rich in N and other essential nutrients and having narrow C: N ratio could be of higher agronomic value.”

In the paper

“Biochar has positive, negative as well as neutral effects on crop productivity.”

In the paper

“The majority of biochar is alkaline, except a few like oak and yellow pine chipped biochar, which is acidic.”

In the paper

“These observations may be explained by increased temperature of biochar pyrolysis resulting in modifications of the types of chemical functional groups (acidic versus ketonic) on the biochar carbon skeletons, which would modify the basicity of the biochar and thus the resulting pH of the soil which was amended by the biochar (Mandal et al., 2016; 2018).”

What the sources say

• Not checked yetcites Mandal et al., 2016; 2018

In the paper

“Many studies showed that biochar significantly influences the mineralization/immobilization turnover of N in soil thereby controlling the N availability without any definite conclusion.”

In the paper

“It is likely that the low sample numbers and high diversity within the samples is such that not much information may be derived from the temperatureapplication rate-yield dataset by PCA.”

In the paper

“This suggests an explanation counter to expectations that greater application rates of biochar result in lower stimulation of crop yield.”