Nitrogênio e metais pesados em área de planossolo da UFRRJ cultivada com soja (Cv. Celeste) após aplicação de resíduos industriais

Abstract

The study was developed with the objective of evaluating the effect of addition of two residues (Ferkal and Mud from the Petroflex Treatment Station of Industrial Residues - LETRIP) in reduction of soil acidity, supply of nutrients, increasing in organic matter content, risk of heavy metal contamination and in the productivity of soy cultivar Celeste, in an area of PLANOSSOLO (Fragiudult). The experiment was developed in an area at the Rural Federal University of Rio de Janeiro campus, during the agricultural year of 2003/04, located in Seropédica, State of Rio de Janeiro (BR). The treatments were set by combination of dosages of 25, 50 and 100 Mg ha-1 of LETRIP with 3 and 6 Mg ha-1 of Ferkal, plus testimony without both residues. The installation of the experimental plots followed the random experimental block design, factorial 4 x 3, with 12 treatments and 3 repetitions, with a total of 36 plots. The useful area of each plot was 16 m2 plus the adjoining area. The soil was plowed on October 3rd, 2003, and the Ferkal residue was applied on October 8th, manually, in amounts equivalent to 3.0 and 6.0 Mg ha-1 of dry matter, and incorporated to the soil with a rotative hoe. LETRIP was applied in the period from November 15th to December 17th, 2003, at the dosage of 25, 50 and 100 Mg ha-1 of dry matter and incorporated with a rotative hoe. The soy was planted from January 13 to 20th, 2004, approximately 40 days after application of residues Ferkal and LETRIP in 50% of the plots area. The spacing among lines was of 40 cm and the density of plants was of 20 plants for linear meter. The useful area of each plot was represented by the three central rows, being discarded a meter of each row ends. The seeds were inoculated with Bradyrizobium japonicum, ancestries BR 29 and BR 96, recommended for the soy culture. It was made A supplement of fertilizer was applied, equivalent to 60 kg ha-1 of P2O5, or 400 kg ha-1 of Termophosphate Yoorin at the planting. The isolated effects of dosages of Ferkal and LETRIP residues showed a linear pattern, with the increase of soy productivity with increasing dosages of each residue. Though, the largest productions were obtained in the combination of dosages of the residues. The highest dosage of combined Ferkal with the highest dosage of LETRIP resulted in productivity higher than 4000 kg ha-1, an increment of productivity of 1300 kg ha-1 when compared to the testimony. The results obtained demonstrated the potential of those residues for agricultural usage, substituting partially mineral fertilizers. However, it is necessary a special care while equilibrating ratios among organic and mineral N ( - +4 N NH and - -3 N NO + - -2 N NO ), and alterations in content of heavy metals, that should be monitored along the time. Also, soil management practices that preserve organic matter should be used.