Residual effect of nitrogen fertilizers formulated with biochar.

Abstract: Biochar-based nitrogen fertilizers provide productivity and efficiency of nitrogen use gains, but knowledge is scarce about the residual effect for subsequent crops. We evaluated the residual effect of biochar-based nitrogen fertilizers formulated with urea and charcoal fines residues from the coal manufacturing process for the supply of the Brazilian steel park. The treatments tested were related to the residual effect of 80 kg Nha-1 applied via side dressing in an experiment with corn cultivation under field conditions. After corn harvesting, soil samples from the 0-15 cm layer were collected from each experimental plot, respecting the treatments represented by the following sources of N, besides the control: ammonium nitrate, urea and three biochar-based fertilizers r (F51/10, F40/17, and F29/20). The soil was placed in pots (3L) and fertilized with macronutrients (except N) and micronutrients. The test plant was black oats (Avena strigosa Schreb) and three shoot cuts of the plants were performed during 84 days of experimentation. The initial levels of inorganic N in soil, dry mass produced (shoot and root) and N content absorbed by black oats were analyzed.The initial concentrations of inorganic N in the soil were similar among nitrogen sources. Some highlight is the higher NO3- concentration for ammonium nitrate, as a result of the low efficiency of N use by corn in the field stage. Plant dry mass and N content confirmed the greatest residual effect for ammonium nitrate, for the above reason, combined with zero loss of NH3 in the field. The residual effect of F51/10 (biochar-based nitrogen fertilizer with 51% biochar and 10% N) was higher than that observed for urea when considering the N content absorbed by oats. The superiority of the F51/10 was credited to the slower N release of this fertilizer, as the losses of NH3 from biochar-based fertilizers were as large or greater than determined for urea.Biochar-based nitrogen fertilizer formulated with urea has a longer residual effect compared to the exclusive application of urea and this effect is related to the slow N release, which demonstrates the potential of this technology in the formulation of enhanced-efficiencyN fertilizers.