Land disposal potential of tobacco processing residues/Potencial de uso agricola de dois residuos de agroindustria fumageira

Brazil is one of the leaders in the production and trading of tobacco leaves in the global market, which results in a large amount of residues that would be recycled and used as soil fertilizers in agriculture. This research aimed to study the land disposal potential and agricultural use of tobacco processing residues (TPRs), their mineralization and the nutrient supply to the plants. The study was carried out in an open area using pots with 32d [m.sup.3] of a sandy soil (Paleudult), provided with water drainage collectors and tilled with three corn plants each. Eighteen treatments were tested with mineral fertilization, poultry manure (PM), earthworm compost (EC) and increasing rates (0, 7.5, 15, 30 e 60t [ha.sup.-1]) of TPR D (dust) and TPR S (stem fibers). Treatments with TPRs (15t [ha.sup.-1]) plus mineral supplementation two by two (NP, NK and PK) were also tested, with four replications each. The experiment started in 01/15/ 2004 and conducted until 03/16/2004, when corn plants were harvested. The response curves showed that the residues application rates between 15 and 20t [ha.sup.-1] are most adequate for the studied soil. The results indicated that both TPRs may be important sources of biomass and potash and have potential to be recycled in the soil, supplying part of the macronutrients required for proper plant growth. Key words: nutrient cycling, nitrogen, water quality. O Brasil e um dos maiores produtores e exportadores mundiais de tabaco em folha, resultando em grandes quantidaes de residuos que poderiam ser utilizados como fertilizantes na agricultura. O objetivo deste trabalho foi avaliar o potencial de reciclagem agricola de dois residuos de agroindustria fumageira (RAF's), sua mineralizacao no solo e liberacao de nutrientes as plantas. O experimento foi conduzido a ceu aberto utilizando como unidades experimentais vasos com capacidade de 32 litros de solo, adaptados com tubo coletor de lixiviado e um argissolo (PVAd), cultivado com tres plantas de milho. Foram feitos 18 tratamentos com adubo mineral, cama-de-aviario, composto organico e com adicao de doses crescentes (0, 7,5, 15, 30 e 60t [ha.sup.-1) dos residuos RAF P (po) e do RAF T (talos), alem de tratamentos com residuos (15t [ha.sup.-1) e complementacao com nutrientes minerais dois a dois (NP, NK e PK), em quatro repeticoes. O experimento foi iniciado em 15/01/2004, tendo sido a parte aerea das plantas colhida em 16/03/2004. Foram avaliados o rendimento do milho e os atributos de fe