Forest Soil Colloids Enhance Delivery of Phosphorus Into a Diffusive Gradient in Thin Films (DGT) Sink

Phosphorus (P) is preferentially bound to colloids in soil. On the one hand, colloids may facilitate soil P leaching leading to a decrease of plant available P, but on the other hand they can carry P to plant roots, thus supporting the P uptake of plants. We tested the magnitude and the kinetics of P delivery by colloids into a P sink mimicking plant roots using the Diffusive Gradients in Thin-Films (DGT) technique. Colloids were extracted with water from three forest soils differing in parent material using a method based on dispersion and sedimentation. Freeze-dried colloids, the respective bulk soil, and the colloid-free extraction residue were sterilized and mixed with quartz sand and silt to an equal P basis. The mixtures were wetted and the diffusive fluxes of P into the DGTs were measured under sterile, water unsaturated conditions. The colloids extracted from a P-poor sandy podzolic soil were highly enriched in iron and organic matter compared to the bulk soil and delivered more P at a higher rate into the sink compared to bulk soil and the colloid-free soil extraction residue. However, colloidal P delivery into the sink was smaller than P release and transport from the bulk soil developed on dolomite rock, and with no difference for a soil with intermediate phosphorus-stocks developed from gneiss. Our results provide evidence that both the mobility of colloids and their P binding strength control their contribution to the plant available P-pool of soils. Overall, our findings highlight the relevance of colloids for P delivery to plant roots.

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Phosphorus dynamics during early soil development in extreme environment

10.5194/soil-2021-65 ◽

2021 ◽

Author(s):

Zuzana Frkova ◽

Chiara Pistocchi ◽

Yuliya Vystavna ◽

Katerina Capkova ◽

Jiri Dolezal ◽

...

Keyword(s):

Isotopic Composition ◽

Soil Development ◽

Parent Material ◽

Available P ◽

Extreme Condition ◽

Organic P ◽

Soil P ◽

Early Stages ◽

P Pools ◽

Microbial P

Abstract. At the early stages of pedogenesis, the dynamics of phosphorus (P) in soils are controlled by microbial communities, the physicochemical properties of the soil and the environmental conditions. While various microorganisms involved in carrying out biogeochemical processes have been identified, little is known about the actual contribution of microbial processes, such as organic P hydrolysis and microbial P turnover, to P cycling. We thus focused on processes driven by microbes and how they affect the size and cycling of organic and inorganic soil P pools along a soil chronosequence in the Chamser Kangri glacier forefield (Western Himalayas). The rapid retreat of the glacier allowed us to study the early stages of soil formation under cold arid climate. Biological P transformations were studied with the help of the isotopic composition of oxygen (O) in phosphate (δ18OP) coupled to sequential P fractionation performed on soil samples from four sites of different age spanning 0 to 100–150 years. The mineral P, i.e. 1M HCl-extractable P, represented still 95 % of the total P stock after approximately 100 years of soil development. Its isotopic composition was similar to the parent material also at the most developed site. Primary phosphate minerals, therefore, mostly composed this pool. The δ18OP of the available P and the P bound to Fe and Al oxides instead differed from that of the parent material, suggesting that these pools underwent biological turnover. The isotopic composition of O in of the available P was mostly controlled by the microbial P, suggesting fast exchanges occurred between these two pools possibly fostered by repeated freezing-thawing and drying-rewetting cycles. The release of P from organic P become increasingly important with soil age, constituting one third of the P flux to available P at the oldest site. Accordingly, the lighter isotopic composition of the P bound to Fe and Al oxides at the oldest site indicated that this pool contained phosphate released by organic P mineralization. Compared to previous studies on early pedogenesis under alpine or cold climate, our findings suggest a much slower decrease of the P-bearing primary minerals during the first 100 years of soil development under extreme condition. However, they provide evidence that, by driving short-term P dynamics, microbes play an important role in controlling the redistribution of primary P into inorganic and organic soil P pools.

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Depletion, accumulation and availability of soil phosphorus in the Askov long-term field experiment

Soil Research ◽

10.1071/sr19203 ◽

2020 ◽

Vol 58 (2) ◽

pp. 117 ◽

Cited By ~ 1

Author(s):

Musibau O. Azeez ◽

Gitte Holton Rubæk ◽

Ingeborg Frøsig Pedersen ◽

Bent T. Christensen

Keyword(s):

Rock Phosphate ◽

Soil Phosphorus ◽

Available P ◽

Soil P ◽

Olsen P ◽

Extractable P ◽

P Application ◽

Plant Available P ◽

Water Extractable

Soil phosphorus (P) reserves, built up over decades of intensive agriculture, may account for most of the crop P uptake, provided adequate supply of other plant nutrients. Whether crops grown on soils with reduced supply of other nutrients obtain similar use-efficiency of soil P reserves remains unclear. In treatments of the Askov Long-Term Experiment (initiated in 1894 on light sandy loam), we quantified changes in soil total P and in plant-available P (Olsen P, water extractable P and P offtake in wheat grains) when P-depleted soil started receiving P in rock phosphate and when P application to soil with moderate P levels ceased during 1997–2017. Additionally we studied treatments with soil kept unfertilised for >100 years and with soil first being P depleted and then exposed to surplus dressings of P, nitrogen (N) and potassium in cattle manure. For soil kept unfertilised for >100 years, average grain P offtake was 6 kg ha–1 and Olsen P averaged 4.6 mg kg–1, representing the lower asymptotic level of plant-available P. Adding igneous rock phosphate to severely P-depleted soil with no N fertilisation had little effect on Olsen P, water extractable P (Pw), grain yields and P offtake. For soils with moderate levels of available P, withholding P application for 20 years reduced contents of Olsen P by 56% (from 16 to 7 mg P kg–1) and of Pw by 63% (from 4.5 to 1.7 mg P kg–1). However, the level of plant-available P was still above that of unfertilised soil. Application of animal manure to P-depleted soil gradually raised soil P availability, grain yield and P offtake, but it took 20 years to restore levels of plant-available P. Our study suggests symmetry between rates of depletion and accumulation of plant-available P in soil.

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A comparison of four resin extractions and 32P isotopic exchange for the assessment of plant-available P

Canadian Journal of Soil Science ◽

10.4141/cjss92-027 ◽

1992 ◽

Vol 72 (3) ◽

pp. 281-294 ◽

Cited By ~ 16

Author(s):

T. Sen Tran ◽

R. R. Simard ◽

J. C. Fardeau

Keyword(s):

Anion Exchange ◽

Isotopic Exchange ◽

Exchange Resin ◽

Anion Exchange Resin ◽

Relative Yield ◽

Available P ◽

Multiple Regression Equation ◽

Fertilizer Response ◽

Soil P ◽

Plant Available P

Resin extraction procedures are widely used to simulate nutrient uptake by plant roots. The objective of this study was to compare an anion exchange resin in three forms: F, Cl and HCO3, and a mixed anionic-cationic exchange resin in H-OH form to a 32P isotopic exchange method in their ability to extract soil P, and to predict plant-available P for oat (Avena sativa L.) grown in the glasshouse. Thirty-four soils varying widely in chemical and physical properties, and in P contents, were extracted for 24 h at a soil-to-solution ratio of 1:80 with 1 g resin. Increasingly higher P quantities were obtained by isotopic exchange after 1 min (E1 7.61 mg kg−1), Cl-resin (27.3 mg kg−1), HCO3-resin (40.5 mg kg−1), F-resin (75.1 mg kg−1) and H-OH resin (130 mg kg−1). The Cl and HCO3 resins extracted a constant ratio of E1-P in strongly acidic and weakly acidic to neutral soils; this was not the case for the other resins. The pH values of the resin-soil-solution system were related to the natural logarithm of the amount of rapidly exchangeable Ca. The Cl and HCO3 resins best predicted P uptake and relative yield of oat growing on 34 soils. These two methods were superior to chemical methods in evaluating soil P status and fertilizer response of oats. The relationships between the amount of soil P desorbed by the HCO3 and F resins and by plant uptake were improved when the P buffering capacity (MBC) was included in the multiple regression equation. The P intensity factor was most important for the H-OH and Cl resins. In general, desorption of soil P with exchange resins improves, compared to chemical extradants, the evaluation of the P-supplying power of soils. Key words: 32P, anion exchange resin, available P, extraction method

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Diffusive gradients in thin films predicts crop response better than calcium-acetate-lactate extraction

Nutrient Cycling in Agroecosystems ◽

10.1007/s10705-021-10173-2 ◽

2021 ◽

Author(s):

Benjamin Hill ◽

Jakob Santner ◽

Heide Spiegel ◽

Markus Puschenreiter ◽

Walter W. Wenzel

Keyword(s):

Thin Films ◽

Spring Barley ◽

P Uptake ◽

Calcium Acetate ◽

P Availability ◽

P Deficiency ◽

Soil P ◽

Eastern Austria ◽

Diffusive Gradients ◽

Better Than

AbstractSoil P testing has been widely used to predict crop yields, P uptake, and fertilizer demands in agriculture. Diffusive gradients in thin films (DGT) provides a zero-sink soil P test which mimics diffusion-controlled plant uptake and has previously been found to predict P availability to crops better than conventional quantity-based P tests in highly weathered Australian, though not in European soils. Here we tested the performance of DGT and the Austrian and German standard P quantity test calcium acetate lactate (CAL) to explain the variation of crop yield and P uptake response of winter wheat (Triticum aestivum L.) and spring barley (Hordeum vulgare L.) in long-term P fertilization experiments at four different sites in eastern Austria. Phosphorus extracted with DGT (P-DGT) and CAL (P-CAL) correlated well in similar soils but not across sites with large variation in soil and site properties such as carbonate equivalent and water availability. The predictive power of DGT for barley (R2 = 0.42) and wheat grain yield (R2 = 0.32), and P uptake in wheat grains (R2 = 0.36) was clearly superior to that of the CAL, and less dependent on soil properties. The better performance of DGT compared to the quantity test is consistent with diffusion-limited P uptake in the water-limited cultivated soils of eastern Austria. The critical values of P deficiency derived from the Mitscherlich-type fits for barley and wheat at 80% relative yield are 64.9 and 26.2 µg L−1, respectively, consistent with differential P demands of the crops.

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Phosphorus dynamics during early soil development in a cold desert: insights from oxygen isotopes in phosphate

SOIL ◽

10.5194/soil-8-1-2022 ◽

2022 ◽

Vol 8 (1) ◽

pp. 1-15

Author(s):

Zuzana Frkova ◽

Chiara Pistocchi ◽

Yuliya Vystavna ◽

Katerina Capkova ◽

Jiri Dolezal ◽

...

Keyword(s):

Isotopic Composition ◽

Soil Development ◽

Parent Material ◽

Cold Climate ◽

Available P ◽

Organic P ◽

Soil P ◽

Early Stages ◽

P Pools ◽

Microbial P

Abstract. At the early stages of pedogenesis, the dynamics of phosphorus (P) in soils are controlled by microbial communities, the physicochemical properties of the soil and the environmental conditions. While various microorganisms involved in carrying out biogeochemical processes have been identified, little is known about the actual contribution of microbial processes, such as organic P hydrolysis and microbial P turnover, to P cycling. We thus focused on processes driven by microbes and how they affect the size and cycling of organic and inorganic soil P pools along a soil chronosequence in the Chamser Kangri glacier forefield (Western Himalayas). The rapid retreat of the glacier allowed us to study the early stages of soil formation under a cold arid climate. Biological P transformations were studied with the help of the isotopic composition of oxygen (O) in phosphate (δ18OP) coupled to sequential P fractionation performed on soil samples (0–5 cm depth) from four sites of different age spanning 0 to 100–150 years. The P bound to Ca, i.e., 1 M HCl-extractable P, still represented 95 % of the total P stock after approximately 100 years of soil development. Its isotopic composition was similar to the parent material at the most developed site. Primary phosphate minerals, possibly apatite, mostly comprised this pool. The δ18OP of the available P and the NaOH-extractable inorganic P instead differed from that of the parent material, suggesting that these pools underwent biological turnover. The δ18OP of the available P was mostly controlled by the microbial P, suggesting fast exchanges occurred between these two pools possibly fostered by repeated freezing–thawing and drying–rewetting cycles. The release of P from organic P becomes increasingly important with soil age, constituting one-third of the P flux to available P at the oldest site. Accordingly, the lighter isotopic composition of the P bound to Fe and Al oxides at the oldest site indicated that this pool contained phosphate released by organic P mineralization. Compared to previous studies on early pedogenesis under alpine or cold climate, our findings suggest a much slower decrease of the P-bearing primary minerals during the first 100 years of soil development under extreme conditions. However, they provide evidence that, by driving short-term P dynamics, microbes play an important role in controlling the redistribution of primary P into inorganic and organic soil P pools.

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Sensitivity of Three Phosphate Extraction Methods to the Application of Phosphate Species Differing in Immediate Plant Availability

Agronomy ◽

10.3390/agronomy9010029 ◽

2019 ◽

Vol 9 (1) ◽

pp. 29 ◽

Cited By ~ 4

Author(s):

Tobias Hartmann ◽

Iris Wollmann ◽

Yawen You ◽

Torsten Müller

Keyword(s):

Soil Phosphorus ◽

Extraction Methods ◽

Available P ◽

Plant Availability ◽

Soil P ◽

Low Concentrations ◽

High Sorption ◽

Phosphate Species ◽

Different Characteristics ◽

Plant Available P

Extractive tests for determining the plant-availability of soil phosphorus (P) give varying results due to the inherently different characteristics of the extraction solution. Generally, classical soil P tests such as the Olsen or calcium acetate/lactate (CAL) method do not give an indication on the total amount of plant available P, but merely give an indication of the equilibrium between soil and extraction solution. It is also not entirely clear which fractions of P are directly determined through the various methods of extraction, i.e., determined P must not be immediately plant available, as is the case for rock phosphate. It is therefore possible that extraction methods either over or under estimate the amount of P available for plant consumption. In this research, we compared three methods of soil P determination (CAL, Olsen and diffusive gradients in thin films (DGT)) with regards to their ability to determine P species (Ca(H2PO4)2, CaHPO4, Ca3(PO4)2 and Inositol-6-hexakisphosphate) added to soils of high sorption capacity, immediately after as well as two weeks after application. For each of the methods, it could be shown that sorption processes in the soil immediately (0 days incubation) fix P to a point where it is not extractable through any of the described methods. These sorption processes continue over time, leading to a further decrease of determined P. The acidic CAL extraction method gives higher results of extractable P compared to the Olsen method. Due to the extraction of Ca3(PO4)2, the CAL method may overestimate immediately plant-available P. The most suitable methods for the determination of immediately plant available P may therefore be the Olsen and DGT methods. Organic IP6 is not determined by any of the extraction methods. At low concentrations of soil P, the DGT method may fail to give results.

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What is the P value of Siberian soils?

Biogeosciences Discussions ◽

10.5194/bgd-12-19819-2015 ◽

2015 ◽

Vol 12 (23) ◽

pp. 19819-19859 ◽

Cited By ~ 1

Author(s):

F. Brédoire ◽

M. R. Bakker ◽

L. Augusto ◽

P. A. Barsukov ◽

D. Derrien ◽

...

Keyword(s):

Regional Scale ◽

Global Scale ◽

Parent Material ◽

Available P ◽

Northern Eurasia ◽

P Value ◽

Slow Kinetics ◽

Wide Range ◽

Agriculture Development ◽

Plant Available P

Abstract. Climate change is particularly strong in Northern Eurasia and substantial ecological changes are expected in this wide region. The reshaping and the migration northward of bioclimatic zones may offer opportunities for agriculture development in western and central Siberia. However, the bioclimatic vegetation models currently employed for projections still do not consider soil fertility whereas it is highly critical for plant growth. In the present study, we surveyed the phosphorus (P) status in the south-west of Siberia where soils are developed on loess parent material. We selected six sites differing by pedoclimate conditions and sampled the soil at different depths down to one meter in aspen (Populus tremula L.) forest as well as in grassland areas. The P status was assessed by conventional methods and by isotope dilution kinetics. We found that P concentrations and stocks, as well as their distribution through the soil profile, were rather homogeneous at the studied regional scale, although there were some differences among sites (particularly in organic P). The young age of the soils, together with slow kinetics of soil forming processes, have probably not yet conducted to a sufficiently wide range of soil physico-chemical conditions to observe more diverging P status. The comparison of our dataset to similar vegetation contexts on the global scale revealed that the soils of south-western Siberia, and more generally of Northern Eurasia, has often (very) high levels of total, organic and inorganic P. The amount of plant-available P in topsoils, estimated by the isotopically exchangeable phosphate ions, was not particularly high, but intermediate at the global scale. However, large stocks of plant-available P are stored in subsurface layers which have currently low fine root exploration intensities. These results suggest that the P resource is unlikely to constrain vegetation growth and agriculture development in the present and near future conditions.

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Effects of withholding fertiliser on pasture production and phosphate cycling in hill country

Proceedings of the New Zealand Grassland Association ◽

10.33584/jnzg.1990.51.1910 ◽

1990 ◽

pp. 17-20

Author(s):

J.S. Rowarth ◽

A.G. Gillingham

Keyword(s):

P Uptake ◽

Available P ◽

Research Centre ◽

Pasture Production ◽

Inorganic P ◽

Hill Country ◽

Olsen P ◽

Plant P Uptake ◽

Dung Decomposition ◽

Plant Available P

A large-scale phosphate (P) fertiliser grazing trial was carried out at Whatawhata Research Centre between 1980 and 1984. The effect of 5 fertiliser rates (10, 20 30, 50 or 100 kg P/ha) on pasture production, plant P uptake, dung P distribution, dung decomposition and Olsen P concentration were monitored on 4 slope groups (campsites, O-10"; easy, 1 I-20"; moderate, 21-30" and steep, 31" +). Soils collected from each slope and fertiliser treatment were used in a pot trial to investigate the size of the plant available P pool. Results can be used to interpret data from field trials where fertiliser has been withheld. Initially, pasture production or Olsen P will change little because the most productive areas of the paddock receive large amounts of dung P which buffer the effect of fertiliser withdrawal. On these areas P is cycled more rapidly than on steep slopes, further buffering the system against P deficiency. Small changes in Olsen P do not reflect the more rapid changes in inorganic P or plant-available P. As inorganic P becomes depleted, plant P uptake decreases. The associated decrease in dung P return and the slower rate of dung decomposition contribute to a slowing of the P cycle. The net effect is less feed and slower regrowth after grazing. Recovering from this state will require not only P fertiliser but also time for high producing pasture species to regenerate. Keywords phosphate cycling, topdressing, fertiliser, pasture production, hill country, dung

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POSISI CONTOH DAUN UNTUK ANALISIS STATUS FOSFOR (P) PADA BIBIT JARAK PAGAR (Jatropha curcas L.) DAN KADAR P TERSEDIA PADA DAERAH PERAKARANNYA

Jurnal Penelitian Tanaman Industri ◽

10.21082/jlittri.v14n4.2008.125-130 ◽

2020 ◽

Vol 14 (4) ◽

pp. 125

Author(s):

A ARIVIN RIVAIE ◽

ELNA KARMAWATI ◽

RUSLI RUSLI

Keyword(s):

Jatropha Curcas ◽

Bulk Soil ◽

Available P ◽

P Availability ◽

Leaf Position ◽

Physic Nut ◽

Soil P ◽

Jatropha Curcas L ◽

Leaf P ◽

Bray 1

ABSTRAK Status P pada tanaman dapat diduga dengan menganalisis kadar P pada daun, karena daun merupakan suatu bagian tanaman yang sangat aktif. Untuk itu, diperlukan informasi posisi daun yang sesuai untuk dijadikan contoh daun untuk analisis status P tanaman. Percobaan ini bertujuan untuk menentukan posisi daun yang sesuai untuk analisis status P dan mempelajari perbedaan antara kadar P tersedia di tanah dan di rhizosphere, serta hubungannya dengan kadar P daun bibit jarak pagar. Percobaan dilakukan di rumah kaca Balai Penelitian Tanaman Rempah dan Aneka Tanaman Industri (Balittri) Pakuwon, Sukabumi, Jawa Barat, pada September 2006 sampai dengan Juli 2007, disusun dalam rancangan acak lengkap (RAL) dengan 3 (tiga) ulangan. Setiap unit percobaan terdiri atas 20 tanaman. Perlakuan yang diuji adalah: (a) daun ke-1 atau daun yang terletak tepat di bawah kuncup daun yang belum mekar sempurna, (b) daun ke-2 atau daun yang terletak setelah/di bawah daun ke-1, (c) daun ke-3, dan (d) daun ke-4. Parameter yang diamati adalah kadar P daun (%), kadar P tersedia di tanah dan rhizosphere yang diukur dengan metode Bray-1 P. Hasil penelitian menunjukkan bahwa daun ke-2 adalah posisi daun yang sesuai sebagai contoh daun untuk analisis status P pada bibit jarak pagar (Jatropha curcas L.). Kadar P di rhizosphere lebih rendah daripada kadar P di tanah (Bray-1P) yang jauh dari akar jarak pagar. Pada daun ke-2, keeratan hubungan yang ditunjukkan oleh koefisien regresi (R2) antara kadar Bray-1 P di rhizosphere dan kadar P daun jarak pagar (R2 = 0.394) lebih tinggi daripada hubungan antara kadar Bray-1 P di tanah dan kadar P daun (R2 = 0.371), sehingga untuk keperluan menggambarkan ketersediaan P tanah atau untuk melihat hubungan P tanah tersedia dengan kadar ataupun serapan P tanaman jarak pagar, akan lebih tepat bila contoh tanah yang diambil berasal dari rhizosphere akar tanaman. Kata kunci: Jarak pagar (Jatropha curcas L.), posisi daun, status P, P tanah tersediaABSTRACT Determination of leaf sample position for analysis of P status in physic nut (Jatropha curcas L.) seedlings and the available P in the root zone Status of P in plants can be quantified by analyzing concentrations of the nutrient in leaf as the leaf is the most active plant part. For this, information on appropriate leaf position as samples for analysis of P status in the plants is needed. A research was conducted with aims to determine an appropriate leaf position of physic nut seedlings and to study differences between the concentrations of available P (Bray-1 P) in the bulk soil and the rhizosphere, along with their relationships with the concentrations of leaf P. The experiment was carried out in a glasshouse of Indonesian Spices and Other Industrial Crops Research Institute, Sukabumi, West Java, from September 2006 to July 2007. The experiment was arranged in a completely randomized design with three replications. Each experimental unit consisted of 20 plants. The treatments were: (a) 1st leaf or a leaf located exactly below the shoot, (b) 2nd leaf or a leaf located below the 1st leaf, (c) 3rd leaf, and (d) 4th leaf. All the leaves were taken from the primary branch of the plants. Parameters measured were P concentrations in the leaf, P concentrations in the bulk soil and the rhizosphere (Bray-1 P). The results showed that the 2nd leaf position was the appropriate leaf position to be taken as samples for the leaf analysis of P status in physic nut (Jatropha curcas L.) seedlings. The concentrations of Bray-1 P in the rhizosphere were lower than that in the bulk soil, which is further away from the roots. The R2 values for the relationships between the Bray-1 P concentrations in the rhizosphere and the the 2nd leaf P concentrations were higher than that between the Bray-1 P concentrations in the bulk soil and the 2nd leaf P concentrations, hence, for the objectives to show the soil P availability or to show the relationships between the available soil P and the concentrations or the P uptake by the physic nut, it will be more accurate if the soil samples are taken from the rhizosphere. Key words: Physic nut (Jatropha curcas L.), leaf position, P status, available soil P

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Could biochar amendment be a tool to improve soil availability and plant uptake of phosphorus? A meta-analysis of published experiments

Environmental Science and Pollution Research ◽

10.1007/s11356-021-14119-7 ◽

2021 ◽

Author(s):

Fitsum Tesfaye ◽

Xiaoyu Liu ◽

Jufeng Zheng ◽

Kun Cheng ◽

Rongjun Bian ◽

...

Keyword(s):

Plant Uptake ◽

P Uptake ◽

Available P ◽

Soil Conditions ◽

P Availability ◽

Vegetable Crops ◽

Soil P ◽

Plant P Uptake ◽

Soil Available P ◽

Biochar Amendment

AbstractAs one of the most important nutrients for plant growth, phosphorus was often poorly available in soil. While biochar addition induced improvement of soil structure, nutrient and water retention as well as microbial activity had been well known, and the effect of biochar soil amendment (BSA) on soil phosphorus availability and plant P uptake had been not yet quantitatively assessed. In a review study, data were retrieved from 354 peer-reviewed research articles on soil available P content and P uptake under BSA published by February 2019. Then a database was established of 516 data pairs from 86 studies with and without BSA in agricultural soils. Subsequently, the effect size of biochar application was quantified relative to no application and assessed in terms of biochar conditions, soil conditions, as well as experiment conditions. In grand mean, there was a significant and great effect of BSA on soil available P and plant P uptake by 65% and 55%, respectively. The effects were generally significant under manure biochar, biochar pyrolyzed under 300 °C, soil pH <5 and fine-textured soil, and soils that are very low in available P. Being significantly correlated to soil P availability (R2=0.29), plant P uptake was mostly enhanced with vegetable crops of high biomass yield. Overall, biochar amendment at a dosage up to 10 t ha−1 could be a tool to enhance soil availability and plant uptake of phosphorus, particularly in acid, heavy textured P-poor soils.

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