Agronomic and environmental efficiency of biochar enriched or not with mineral source in the supply of nitrogen.

Abstract

Since the first studies with Terra Preta de Índio in Brazilian Amazon, where the high fertility was associated with the carbon present in the form of coal, the use of carbonized material in agriculture, called biochar (BC), is now promising. An important waste of charcoal production are coal fines (particles smaller than 10 mm), which can represent up to 15% of the coal produced. In Brazil, research initiatives with BC are more recent, but follow the global standard, in which most of the information and data were generated under controlled conditions (greenhouse or lab conditions), and usually with application of high doses of BC in soil (> 50 t ha-1). The goal of the proposal is to evaluate the use of BC (coal fines) in physical mixture with mineral nitrogen fertilizer or formulated as organic-mineral in the agronomic efficiency for maize and for the N2O emission. The BC will be characterized for pH, electrical conductivity, ash, moisture, CHN elemental composition, CTC, nutrients and description of the structure by means of scanning electron microscopy. The amount and speed of N release will be investigated through experiments with leaching columns, with eight treatments and three replications. The treatments are: BC; two mineral fertilizers; physical mixture of BC and mineral fertilizers and three formulated of BC and fertilizer (organic-mineral). In the leachate will be determined volume, pH and concentrations of inorganic N. The results will be fit to mathematical equations, preferably from chemical kinetics (exponential model) for characterizing the process as a function of time. In the field, in two consecutive cycles of maize, will be evaluate the agronomic efficiency and environmental effectiveness of BC enriched or not with mineral fertilizer (N). The experiment will be randomized blocks, with six treatments and four replications. All parcels will receive fertilization with P and K and the treatments will be: control (without N); mineral N at sowing and coverage; 50 t ha-1 BC applied in total area and fertilization with mineral N at sowing and coverage; 700 kg ha-1 BC in sowing and fertilizing with mineral N at sowing and coverage; 50% of N at sowing via BC formulated with mineral source (organic-mineral) and 50% mineral N; and 100% of N via BC formulated (organic-mineral). It will be determine the content and accumulation of N in plant, apparent efficiency of N, apparent recovery of N, productivity and use efficient of N. During the maize growing the N2O emissions will be quantified from the soil, with the main aim to determine the N2O emission factor. The results will be statistically analyzed by F test for the variances and 5% Tukey test for comparison of means between treatments.