No abstract

Biochar has been used worldwide as an efficient soil amendment due to its beneficial interaction with soil particles and nutrients; however, studies on the effect of biochar on the availability of nutrients such as N and P in tropical soils are still missing. The objective of the study was to evaluate the effect of different types and doses of biochars on the concentration and uptake of N and P in Indian mustard plants (Brassica juncea L.) grown in a Cu contaminated soil during three successive growth cycles. The greenhouse experiment was set up as randomized block design in a 3x3 factorial scheme, with 3 types of biochars (coconut shell, orange bagasse and sewage sludge) and three rates of application (0, 30 and 60t ha-1), and 4 replicates. Biochar increased plant growth by approximately 30 to 224%; however, the orange bagasse biochar was the most effective. Biochar reduced plant N concentration in approximately 15-43%, regardless of the rate of application, indicating the need to carefully adjust N fertilization. In the last growth cycle, biochar from coconut shell and orange bagasse improved the N uptake efficiency suggesting a better amelioration effect with ageing in soil. Biochar did not affect P nutrition in Indian mustard to a great extent; however, it significantly decreased the N:P ratio in the plant.

Biochar, pyrolyzed organic waste for agronomic and environmental purposes, is a viable alternative to improve soil quality in small farm areas in the state of Sergipe, where there is a shortage of water and chemical inputs. This study evaluated the effect of single and simultaneous application of doses (t ha-1) of sewage sludge (SS) and dry coconut shell (CS) on some soil properties and sunflower growth and nutrition (Helianthus annuus L.), in São Cristóvão-SE. The experiment was carried out in a completely randomized scheme, with 6 treatments (1. SE60CS0; 2. SE30CS0; 3. SE20CS10; 4. SE10CS20; 5. SE0CS30; 6. Control (without biochar) and 5 repetitions. In the soil, pH, electrical conductivity, organic carbon, and P, K, and Na concentrations were determined. In the plant, biomass, height, chlorophyll content, and N, P, and K were evaluated. Alone, coconut biochar increased the soil pH but reduced plant N. The sludge biochar did not increase soil pH but improved the soil N and P levels, plant growth (25%), and inflorescence (33%), indicating greater benefits of joint application. In addition to improving productivity, biochar, both from sewage sludge and dry coconut shell, can improve the destination and management of these residues and, at the same time, promote the recycling of nutrients in soil.