José Henrique De Souza Júnior

Biochar comes from organic biomass and is used to improve agricultural productivity. However, its variable chemical composition limits its classification and effective use. Thus, the objective of this study was to characterize the nutrient contents and properties of different biochars produced in the southern Agreste region of Pernambuco. The research was developed at the Federal University of Agreste de Pernambuco (UFAPE), where biochars are produced from sewage sludge (B1), grape fermentation (B2), cashew wood (B3), chicken litter (B4) and beans (B5) via a slow pyrolysis process. Standard Embrapa and Iac methodologies were followed in the chemical analyses. Principal component analysis (PCA) was used to identify specific characteristics that made them suitable for use in different soil types. PCA revealed that the first four main components (PC1, PC2, PC3 and PC4) explained 100% of the total data variability. PC1 was defined by variables such as C, H and pH. PC2 was positively correlated with nutrient content and CEC. PC3 and PC4 were positively correlated with K, N, P and Mg. On this basis, the use of B1 is indicated for soils with high levels of organic matter, B2 is indicated for soils deficient in elements such as N and K, B3 and B5 are indicated before its use, its association with other sources of nutrients is necessary, and B4 is recommended for soils poor in P and Ca.

O estudo foi conduzido para investigar as propriedades de biochars produzidos a partir de diferentes materiais, com foco na capacidade de adsorção e dessorção de fosfato, elemento decisivo para a gestão eficiente do fósforo em solos agrícolas. Foram analisados três tipos de biochar: lodo de esgoto, cama de frango e madeira de cajueiro. A composição mineralógica dos biochars foi determinada por difração de raios X. A capacidade de adsorção e dessorção de fosfato foi avaliada utilizando as isotermas de Langmuir e Freundlich, e as quantificações do fosfato adsorvido e dessorvido foram realizadas por meio de centrifugação e análises colorimétricas. O biochar de madeira de cajueiro apresentou a maior área superficial específica e eficácia na retenção de fosfato, seguido pelo biochar de lodo de esgoto, sendo o biochar de cama de frango o menos eficiente. As curvas de dessorção indicaram uma liberação lenta de fosfato, sugerindo que parte do fosfato adsorvido foi retida pelos biochars e se tornou menos disponível para liberação. O biochar de madeira de cajueiro foi o mais eficaz na retenção de fósforo entre os biochars estudados. A adsorção de fosfato pelos biochars seguiu uma tendência dependente da concentração, destacando a importância da caracterização mineralógica na avaliação da reatividade química e da capacidade de adsorção dos biochars.

Biochar has received increasing attention as a soil conditioner, being known for its ability to confer numerous benefits to the soil. Derived from the thermal decomposition of organic materials under low levels of oxygen, biochar concentrates essential nutrients and carbon while having low carbon dioxide emissions. Our hypothesis is that biochar applied as a top dressing can improve soil microbial attributes even after two years in a soil cultivated with different grape varieties. To test this hypothesis, we conducted a field experiment using different doses of cashew wood biochar applied to two grape varieties and evaluated its residual effect on microbial biomass and soil enzymatic activities. The design used was a randomized block design, in a 4 x 2 factorial scheme, with five replications: four doses of biochar (0, 5, 10 and 15 ton ha-1) and two grape varieties (Cabernet sauvignon and Malbec). Soil collection was carried out at a depth of 0-20 cm, to evaluate total organic carbon, microbial biomass carbon and soil enzymatic activities. Our findings revealed that the effect of grape varieties on soil biological properties was more pronounced than the biochar dose, indicating that there is a small residual effect of biochar doses after 2 years of application. Overall, our study provides important insights into the residual effect of biochar on soil microbial attributes and is considered an ecologically sustainable alternative, as it solves the problem of waste reuse and provides a disposal that brings benefits to soil properties.

Nowadays, the development of low-cost technologies that help the rural producer in raising the productivity of crops with environmental concern is essential. From this, the objective of the present work was to evaluate doses of humic substances as an alternative for the production of squash seedlings. The research was developed at the University of the State of Bahia - UNEB, in Euclides da Cunha - Bahia, using the Moranga Exposure cultivar. The experimental design adopted was completely randomized with 3 compounds and 5 doses, with 15 treatments and 5 repetitions for each compound dose, in a 3x5 factorial scheme. The doses of humic substances used were 0, 0.5, 1.0, 2.0 and 4.0 mL/plant^-1. The following variables were analyzed: number of leaves, stem diameter, plant height, chlorophyll content, root length, shoot dry mass and root dry mass. Based on the results found, it was concluded that the dose of 0.5 mL/plant^-1 provided squash seedlings with a greater number of leaves (3.4), plant height (25.2 cm), stem diameter (0.68 mm), chlorophyll content (40.1 µg.cm^-2), root length (31.40 cm), shoot dry mass (1.78 g), root dry mass (0.35 g). It was also possible to observe that the dose of 4.0 mL/plant-1 and the absence of humic substances in the dose of 0 mL/plant^-1 had a limiting effect on the development of the culture. Thus, doses of 0.5 mL/plant^-1 are indicated for the production of squash seedlings in the semi-arid region.