Abstract
Abstract Background The use of sulfuric acid (SA) to acidify biochars is known to enhance their phosphorus (P) fertilizer value. Potentially, biological approaches such as lowering the pH of biochar by lactic acid co‐fermentation or applying biochar with a nitrification inhibitor (NI) to reduce rhizosphere pH are an alternative to SA. Aim This study aimed to evaluate the two methods for increasing plant P availability from two biochars and compare them with SA‐treated biochars (as a reference) in a pot experiment. Methods Meat and bone meal biochar (MB‐C) and digestate solids biochar (DS‐C) were bio‐acidified (BA) by lactic acid fermentation with organic waste. The untreated, SA‐treated, BA biochars, and biochars co‐applied with a NI (3,4‐dimethylpyrazolephosphate) were tested in a pot experiment with maize. Results The fermentation reduced the pH of the organic waste biochar mixtures to <4.3 and increased water‐extractable P (WEP) to 30% of total P. The untreated biochars had a mineral fertilizer replacement value of >50% and SA increased replacement values to ≈100%. The application of NI did not affect rhizosphere pH or P uptake. The BA MB‐C increased soil solution P concentration, but P uptake did not significantly increase. The application of the BA DS‐C raised soil pH and reduced plant P uptake and biomass. Conclusion The untreated biochars showed considerable P fertilizer effectiveness, suggesting that acidification may not always be necessary. Rhizosphere acidification and the bio‐acidification of biochars were not effective in further increasing P uptake, despite higher levels of WEP.
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Claims 10
Claim · model-written summary
Lactic acid fermentation reduced the pH of organic waste biochar mixtures to below 4.3.
- Treatment
- fermentatione1
- Outcome
- pH of the organic waste biochar mixturese1
- Direction
- reducede1
- Value
- <4.3e1
Zea maysNot reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pot experiment with maize”
e1“The fermentation reduced the pH of the organic waste biochar mixtures to <4.3 and increased water-extractable P (WEP) to 30% of total P”
Claim · model-written summary
Fermentation increased water-extractable P of the organic waste biochar mixtures to 30% of total P.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pot experiment with maize”
e1“The fermentation reduced the pH of the organic waste biochar mixtures to <4.3 and increased water-extractable P (WEP) to 30% of total P”
Claim · model-written summary
Untreated biochars had a mineral fertilizer replacement value of more than 50% in maize.
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pot experiment with maize”
e2“The untreated biochars had a mineral fertilizer replacement value of >50% and SA increased replacement values to ≈100%”
Claim · model-written summary
Sulfuric acid treatment increased the mineral fertilizer replacement value of biochar to about 100%, above untreated biochars.
- Treatment
- SAe2
- Outcome
- replacement valuese2
- Direction
- increasede2
- Value
- ≈100%e2
- Comparator
- untreated biocharse2
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pot experiment with maize”
e2“The untreated biochars had a mineral fertilizer replacement value of >50% and SA increased replacement values to ≈100%”
Claim · model-written summary
Nitrification inhibitor application did not affect rhizosphere pH or P uptake in maize.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pot experiment with maize”
e3“The application of NI did not affect rhizosphere pH or P uptake”
Claim · model-written summary
Bio-acidified MB-C biochar increased soil solution P concentration in the maize pot experiment.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pot experiment with maize”
e4“The BA MB‐C increased soil solution P concentration, but P uptake did not significantly increase”
Claim · model-written summary
Bio-acidified MB-C biochar did not significantly increase maize P uptake.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pot experiment with maize”
e4“The BA MB‐C increased soil solution P concentration, but P uptake did not significantly increase”
Claim · model-written summary
Bio-acidified DS-C biochar raised soil pH in the maize pot experiment.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pot experiment with maize”
e5“The application of the BA DS‐C raised soil pH and reduced plant P uptake and biomass”
Claim · model-written summary
Bio-acidified DS-C biochar reduced maize plant P uptake and biomass.
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pot experiment with maize”
e5“The application of the BA DS‐C raised soil pH and reduced plant P uptake and biomass”
Claim · model-written summary
The authors suggest acidification of biochar may not always be necessary for P fertilizer use.
- Outcome
- acidification may not always be necessarye6
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“pot experiment with maize”
e6“suggesting that acidification may not always be necessary”
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