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The sugar and bioethanol industry generate large amounts of filter cake and vinasse, residues that are applied to sugarcane fields as conditioners and organic fertilizers. However, these may be significant sources of greenhouse gases emissions to the atmosphere. This study assessed the impact of sugarcane straw biochar on the emissions of CO 2 , CH 4 and N 2 O promoted by filter cake and vinasse applied to soil, and its effects on the chemical properties and bacterial communities of a Typic Hapludox and a Quartzipsamment. A laboratory incubation was conducted for 100 days with both soils under five treatments: vinasse and filter cake amendment (FV), plus biochar at 10 (FV + B10), 20 (FV + B20) and 50 (FV + B50) Mg•ha −1 , and a control. Soil pH, available P and exchangeable base contents increased with biochar added to sandy soil. Mineral N decreased with biochar addition to both soils. The FV treatment increased CO 2 emissions by 5-fold and 2.4-fold in sandy and clayey soils, respectively, compared to the control. Moreover, FV +B10 increased CO 2 emissions by 4% and 6.4% in sandy and clayey soils, respectively, compared to FV. Cumulative N 2 O emissions in FV were 537% and 125% higher in sandy and clayey soils, respectively, compared to the control. Nevertheless, increasing biochar amendment rates reduced N 2 O emissions from 24% to 34% in sandy soil, and from 14% to 56% in clayey soil. CH 4 emissions were negligible. The effects of filter, vinasse and biochar amendments on soil amelioration were closely related to its buffering capacity. Temporal changes on bacterial community structure were more pronounced in the sandy soil compared to clayey, and indicated that N 2 O emission mitigation in clayey soil was

Knowledge of soils in the Amazon rainforest is becoming increasingly essential due to dynamics adopted by farmers that substitute forest for pastures, together with growing pressure from diverse segments of society towards adoption of sustainable production systems. The objective of this study was to characterize the soils along two toposequences, one under forest (F) and the other under pasture (P), and to verify how the change in land use influences soil attributes, evaluating their inclusion in the Brazilian Soil Classification System (SiBCS). The soils were sampled in pits located at the summit, backslope and footslope positions for morphological, chemical, physical, and clay mineralogy analysis. The results show that the soils are chemically poor and predominately kaolinitic. Sandy and loamy sand soils are in the surface horizons, with an increase in clay content with depth. The highest values of bulk density and lowest values of macroporosity were observed in the Bt horizons due to the change from a granular structure in the surface to an angular and subangular blocky structure in these horizons. The morphological properties observed in the field are strongly influenced by the annual soil water dynamics, the parent material, and the landscape, representing diagnostic characteristics that influenced classification of the soils, such as aquic with episaturation (epirredóxico), saprolitic, and gravelly. These diagnostic characteristics in the Argissolo Amarelo (Hapludults) are important morphological properties that have not been highlighted by the current edition of the SiBCS.

Visual symptoms of Zn deficiency, induced by excessive P applications, have been observed in commercial orchid nurseries. The supply of other metallic micronutrients, such as Fe and Mn, may also be inadequate in the plant due to high application rates of P. The aim of this study was to investigate this interaction in the nutrition of Phalaenopsis plants. Experimental treatments consisted of three P rates . Dry matter production was evaluated, as well as the levels of P, Zn, Fe, and Mn in both shoots and roots. Higher P rates induced higher shoot dry matter production. However, symptoms of Zn deficiency were observed in plants treated with the highest P rate in the absence of Zn. With increasing P rates, Zn concentrations in the shoots decreased more markedly than in roots, with accumulation of the element in the roots, indicating low Zn translocation to the shoot. A much higher Mn content in shoots (661 mg kg ) suggested that the species is highly tolerant to this micronutrient. The Fe concentrations in the plant were much higher than those indicated in the literature as critical levels for this genus.

No abstract

Increases in greenhouse gases (GHG) emissions, upon changes in land use and agricultural management, lead to a search for techniques that enhance carbon residence time in soil. Pyrolysis increases the recalcitrance of organic materials and enhances their activities as physical, chemical and biological soil conditioners. Emissions of CO 2 , CH 4 and N 2 O quantified from a sandy soil that was treated with three rates (12.5, 25 e 50 Mg•ha −1 ) of either non-pyrolysed poultry manure and sugarcane straw or biochars, pyrolysed at two contrasting temperatures (350˚C and 650˚C). Subsequently, the flux of the three gases was converted and compared in a standard unit (CO 2 eq). The added biochars, significantly reduced GHG emissions, especially CO 2 , relative to the non-pyrolysed materials. The greatest differences between applied rates of poultry manure, relative sugarcane straw, both to biochar and raw material, and the positive response to the increase of pyrolysis temperture, confirm the importance of raw material choice for biochar production, with recalcitrance being an important initial characteristic. Greater emissions occurred with intermediate rate of biochars (25 Mg•ha −1 ) amendment to the soil. These intermediate rates had higher microbial biomass, provided by an intermediate C/N ratio derived from the original soil and the biochar, promoting combined levels of labile C and oxygen availability, leading to an optimal environment for microbiota.

Due to environmental issues, many methods of exploiting renewable natural resources are alternatives to reduce the dependence on non‐renewable agricultural inputs. Phosphate fertilization on weathered tropical soil and waste reuse, for example, requires better management strategies. Thus, biochar from organic residues can be a strategy to reduce pressure on natural resources, in addition to having the potential to mitigate climate change. This study aimed to evaluate the availability of P in tropical soils from the interaction of biochar and arbuscular mycorrhizal fungi (AMF) in the aboveground and root systems of the plant and its impact on greenhouse gas (GHG) emissions. The results indicated that the addition of biochar was an alternative for C sequestration and GHG mitigation, causing no damage to the plant. The applied biochar amount had, for the most part, emission equal to or less than the control treatment (soil only). The sugarcane straw biochar (BCS) showed higher emissions, mainly in the presence of P and AMF. Biologically speaking, there was no significant effect in the presence of mycorrhizae. However, with regard to plant production, treatments where mycorrhizae were inoculated, longer and wider leaves were found. In the production of maize (Zea mays L.) plant material (aboveground and root), the upper and lower values were related to the poultry manure biochar (BPM) , and the presence of P, the values were lower, indicating that, for the good development of the plant, only the presence of the biochar is sufficient, without requiring the addition of phosphate fertilizer.

Core Ideas Biochar mitigates greenhouse gas (GHG) emissions when applied to soils. The reduction in biochar pH leads to higher GHG mitigation. Enhancing biochar pyrolysis temperature also leads to higher GHG mitigation. CO2 emission is explained negatively by the variables soil texture and biochar pH. CO2 emission is explained positively by pyrolysis temperature and biochar dose. Biochar, a pyrolysis product, has the potential to reduce greenhouse gas (GHG) emissions while increasing the soil water holding capacity. The purpose of this paper is to model biochars GHG emission based on its applied dose, its pH value, pyrolysis temperature and soil texture. Poultry manure and sugarcane straw biochar produced at two temperatures (350 and 650°C), were applied in three doses (12.5, 25, and 50 Mg ha−1), to sandy and clayey soils at two soil pH values (original 7.5 and adjusted to 5.5). The concentrations of CO2, CH4 and N2O were determined using gas chromatography. Increasing the biochar pyrolysis temperature and reducing the soil pH to 5.5 reduced the CO2, CH4, and N2O emissions from the soil. The mitigating effect of biochars was more evident in the sandy soil, since the clayey soil was highly buffed. The CO2 emission, explained negatively by the variables soil texture and biochar pH and positively by the variables pyrolysis temperature and biochar dose, had the final equation: CO2 = 82.28 – 0.05Cclay – 0.08pH + 6.98Tpyrolysis + 0.64Dbiochar (R2 = 0.65).