Monoammonium phosphate (MAP), triple superphosphate (TSP), and phosphoric acid (H3PO4), with and without the addition of magnesium oxide (MgO), were mixed with poultry litter (PL) to produce biochar-based fertilizers (BBFs). This is a novel approach aiming to add value to PL residue and to increase P use efficiency in acidic tropical soils. Samples of BBFs were assessed by P-release kinetics in water, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and a bioassay with maize in a greenhouse using a clayey Oxisol. Addition of MgO reduced the kinetics of P released from BBFs impregnated with all P sources. XRD analysis showed the formation of low-solubility Ca2P2O7 and Mg2P207 compounds, which is supported by POP or PO stretching observed in the FTIR spectra. The MgO-treated BBFs increased shoot dry matter production compared to the control, but were inferior when compared to TSP in the short term. The slow release of P and the alkaline reaction of the BBFs show great potential for these materials to be used as enhanced P fertilizers in tropical soils.

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resumoA utilização do solo sob cerrado tem acarretado modificações nas suas propriedades, bem como no comportamento e qualidade da sua matéria orgânica. o cerrado piauiense vem sendo alvo de exploração sem a devida preocupação com a manutenção dos recursos naturais, onde os sistemas de produção têm se caracterizado pelo uso intensivo do solo. o objetivo desta pesquisa foi avaliar o efeito da utilização agrícola na alteração dos atributos biológicos e na dinâmica da matéria orgânica em latossolos Amarelos distróficos típicos, cultivados com soja. o trabalho foi realizado na serra do Quilombo, localizada no cerrado piauiense. Foram verificadas as alterações nos atributos do solo em decorrência da utilização agrícola, que foi iniciada com plantio convencional, posteriormente substituído pelo sistema plantio direto. Foram amostrados solos com diferentes históricos de uso: Pc7/PD8 -sete anos de plantio convencional e oito de plantio direto; Pc5/PD4 -cinco anos de plantio convencional e quatro de plantio direto; Pc3/PD3 -três anos de plantio convencional e três de plantio direto; e cn -solo com cerrado nativo. os atributos avaliados foram: respiração basal do solo, carbono da biomassa microbiana, quociente metabólico, quociente microbiano, carbono orgânico total e nitrogênio total. Para avaliar a dinâmica da matéria orgânica, foi feito o fracionamento físico. os dados foram submetidos à análise de variância. os resultados indicaram que o manejo imposto ao solo com cultivo

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Converting abundant agricultural residues to valuable products, such as biochar, is a pressing challenge for society. Here, our objective has been to produce biochar-based fertilizers (BBFs) with high carbon stability, high yield, and characteristics favorable for their use in soils. Thus, H 3 PO 4 with and without MgO was co-pyrolyzed with coffee husk and poultry litter. Proximate analysis, total phosphorus and magnesium, biochar yield, carbon retention, and thermal and chemical carbon stability were assessed. The BBFs were slightly acidic (pH ∼6.0) and showed high contents of total P (146−206 g kg −1 ) and total Mg (96−98 g kg −1 ), similar to commercial fertilizers. Biochar yield increased up to 65% when treated with H 3 PO 4 and H 3 PO 4 −MgO, resulting in up to 78% greater carbon retention. BBFs showed higher thermal stability, by thermogravimetric analysis and muffle oxidation, when compared to corresponding pristine biochars. Conversely, the addition of H 3 PO 4 −MgO decreased the chemical stability (higher H 2 O 2 and K 2 Cr 2 O 7 oxidation), compared to the biochars, because of the increase in surface area and reactivity. We concluded that the co-pyrolysis of biomasses with H 3 PO 4 and MgO promoted thermal stabilization (increased yield) and increased chemical oxidation, because of increased surface area and reduced crystallinity of the BBFs.