Biochar Phosphorus Release Is Limited by High pH and Excess Calcium

Buss, Wolfram; Assavavittayanon, Kamonchanard; Shepherd, Jessica G.; Heal, Kate; Sohi, Saran

doi:10.2134/jeq2018.05.0181

Cited by 21 publications

(10 citation statements)

References 25 publications

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“…This may be a contributing factor to the decreased PO 4 -P content observed from T 1 to T 2 . A similar finding was reported by Buss et al (2018), where a reduction in P release from BC over a series of extractions was observed. Almost 17% of the total P content (258 ± 2.9 mg kg −1 ) was initially released in the first extraction step, and successively less P at the second (137 ± 2.4 mg kg −1 ) and sixth (34 ± 0.8 mg kg −1 ) extraction steps.…”

Section: Phosphorous (Po 4 -P)supporting

confidence: 89%

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The influence of hydrochar from biogas digestate on soil improvement and plant growth aspects

Jager

Röhrdanz

Giani

2020

Biochar

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Hydrochar (HC), produced by hydrothermal carbonization, offers technical advantages over biochar (BC) produced by pyrolysis, and is suitable for soil amelioration, carbon sequestration, and enhanced plant growth. BC grain size has been shown to influence nutrient retention, microbial colonization and aggregate formation; however, similar research for HC is lacking. Pot trials were conducted to investigate the influence of HC grain size [coarse (6.3-2 mm), medium (2-0.63 mm) and fine (< 0.63 mm)], produced from biogas digestate, for soil improvement in three soils: loamy Chernozem, sandy Podzol, and clayey Gleysol, at a 5% HC application rate (w/w). All soils including two controls (with and without plants) were analysed for water holding capacity (WHC), cation exchange capacity (CEC), wet aggregate stability, pH, plant available nutrients (PO 4 -P, K and N min ) and germination and biomass success using standard laboratory and statistical methods. Soil pH showed a compensatory shift toward the HC pH (7.2) in all soils over the course of the study. For example, the pH of the medium grained HC treatment for the Chernozem decreased from 7.9 to 7.2 and increased in the Podzol and Gleysol from 5.9 to 6.1 and 4.9 to 5.5, respectively. The nutrient-rich HC (2034 ± 38.3 mg kg −1 PO 4 -P and 2612.5 ± 268.7 mg kg −1 K content) provided only a short-term supply of nutrients, due to the relatively easily mineralized fraction of HC, which allowed for quick nutrient release. The pH and PO 4 -P effects were most pronounced in the fine grained HC treatments, with a ~ 87%, ~ 308% and ~ 2500% increase in PO 4 -P content in the Chernozem, Podzol and Gleysol, respectively, compared to the controls at the beginning of the study. The same trend was observed for the K and NH 4 + content in the fine and medium grained HC treatments in all soils. No seed germination inhibition of Chinese cabbage was observed, with average germination rates > 50% in all soils. An effect on NO 3 − content was indeterminable, while there was little to no effect on biomass production, WHC, CEC and aggregate stability. In conclusion, the application of 5% fine grained HC significantly influenced the nutrient content over a short-term. However, the application rate was insufficient to substantially improve plant growth, nor to sustain a longer-term nutrients supply, regardless of grain size.

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Section: Phosphorous (Po 4 -P)supporting

confidence: 89%

“…The optimal pH range for the availability of P to plants is 6.0-6.5 (Buss et al 2018), which all soil types were approaching during the course of this study i.e. from T 1 to T 2 (see Fig.…”

Section: Phosphorous (Po 4 -P)mentioning

confidence: 88%

The influence of hydrochar from biogas digestate on soil improvement and plant growth aspects

Jager

Röhrdanz

Giani

2020

Biochar

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“…Meta‐analyses have found that biochar application commonly increases P availability, particularly when applied to acidic or neutral soils, and for biochar produced from low C:N feedstocks (e.g., manure, crop residues), and produced at low temperatures (Gao et al, 2019; Glaser & Lehr, 2019). However, P availability can be low in Ca‐rich and K‐poor feedstocks such as sewage sludge (Buss et al, 2018, 2020; Torres‐Rojas et al, 2020; Wang et al, 2019) because pyrolysis can convert plant‐available organic P into inorganic P that is less available in the short term (Buss et al, 2020; Rose et al, 2019). The opposite has also been observed, with pyrolysis increasing plant‐available P although decreasing water‐extractable P (Wang et al, 2014; Zwetsloot et al, 2015, 2016).…”

Section: Mechanisms Of Biochar Effects On Soil and Plantsmentioning

confidence: 99%

“…The opposite has also been observed, with pyrolysis increasing plant‐available P although decreasing water‐extractable P (Wang et al, 2014; Zwetsloot et al, 2015, 2016). The effect of biochar on P availability is determined by microscale effects on soil pH and soil solution composition, especially Ca content (Buss, Assavavittayanon, et al, 2018; Buss et al, 2018). Biochar can retain nutrients, especially N, released as fertilizers dissolve, and nutrients already present in soil, reducing loss through leaching (Haider et al, 2020).…”

Section: Mechanisms Of Biochar Effects On Soil and Plantsmentioning

confidence: 99%

How biochar works, and when it doesn't: A review of mechanisms controlling soil and plant responses to biochar

et al. 2021

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We synthesized 20 years of research to explain the interrelated processes that determine soil and plant responses to biochar. The properties of biochar and its effects within agricultural ecosystems largely depend on feedstock and pyrolysis conditions. We describe three stages of reactions of biochar in soil: dissolution (1–3 weeks); reactive surface development (1–6 months); and aging (beyond 6 months). As biochar ages, it is incorporated into soil aggregates, protecting the biochar carbon and promoting the stabilization of rhizodeposits and microbial products. Biochar carbon persists in soil for hundreds to thousands of years. By increasing pH, porosity, and water availability, biochars can create favorable conditions for root development and microbial functions. Biochars can catalyze biotic and abiotic reactions, particularly in the rhizosphere, that increase nutrient supply and uptake by plants, reduce phytotoxins, stimulate plant development, and increase resilience to disease and environmental stressors. Meta‐analyses found that, on average, biochars increase P availability by a factor of 4.6; decrease plant tissue concentration of heavy metals by 17%–39%; build soil organic carbon through negative priming by 3.8% (range −21% to +20%); and reduce non‐CO2 greenhouse gas emissions from soil by 12%–50%. Meta‐analyses show average crop yield increases of 10%–42% with biochar addition, with greatest increases in low‐nutrient P‐sorbing acidic soils (common in the tropics), and in sandy soils in drylands due to increase in nutrient retention and water holding capacity. Studies report a wide range of plant responses to biochars due to the diversity of biochars and contexts in which biochars have been applied. Crop yields increase strongly if site‐specific soil constraints and nutrient and water limitations are mitigated by appropriate biochar formulations. Biochars can be tailored to address site constraints through feedstock selection, by modifying pyrolysis conditions, through pre‐ or post‐production treatments, or co‐application with organic or mineral fertilizers. We demonstrate how, when used wisely, biochar mitigates climate change and supports food security and the circular economy.

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“…These factors interact to determine the P that is available inside and around biochar TA. High levels of Ca could limit the release of P from the high-pH interior of VCZ and Reference biochar (Buss et al 2018). The proportional decrease in available P from VCZ biochar treatments was, however, signi cantly smaller than for TSP fertilizer.…”

Section: Morphological and Spatial Root Responses To Sources Of Phosphorusmentioning

confidence: 99%

Preferences of Pinus Sylvestris Seedling Roots for Different Phosphorus Sources under Phosphorus-Deficient Conditions

Lei

Creber

Bol

et al. 2022

Preprint

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PurposePhosphorus (P) is a limiting nutrient in many managed forests. To further understand the risks and benefits of biochar as a sustainable P source in forest management, an improved mechanistic understanding of its interactions in root systems is required.MethodsA rhizobox experiment was conducted to observe root response of P. sylvestris (Scots pine) seedlings to different biochars in comparison to triple superphosphate (TSP) fertilizer as a P source. Three types of wood-derived biochar were compared: biochar from mixed softwood pellets (“Reference biochar”); from the vascular cambium zone of Picea sitchensis (Sitka spruce) (“VCZ biochar”) and from mixed softwood pellets infused with TSP (“Processed biochar”). These alternative types of biochar presented a range of available P from low to high. The activity of roots in the rhizoboxes was monitored and analyzed using spatial GIS software.ResultsThe total length of P. sylvestris roots did not significantly differ between treatments. However, roots showed strong preference for soil proximal to VCZ biochar and strong avoidance to TSP fertilizer. There was a milder avoidance effect for Processed biochar. Different preferences were mainly explained by available P: roots favored a moderate, sustained P source and avoided sources of high available P. The avoidance effect can be attributed partially to a considerable drop in soil pH around TSP fertilizer. ConclusionThe concentration and duration of P availability affects the root response of P. sylvestris to sources of P. In P-deficient conditions, the development of P. sylvestris roots can be markedly improved by introducing biochar with a certain native P content.

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Biochar Phosphorus Release Is Limited by High pH and Excess Calcium

Cited by 21 publications

References 25 publications

The influence of hydrochar from biogas digestate on soil improvement and plant growth aspects

The influence of hydrochar from biogas digestate on soil improvement and plant growth aspects

How biochar works, and when it doesn't: A review of mechanisms controlling soil and plant responses to biochar

Preferences of Pinus Sylvestris Seedling Roots for Different Phosphorus Sources under Phosphorus-Deficient Conditions

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