NÍVEIS DE LODO DE ESGOTO NA PRODUTIVIDADE DO GIRASSOL

Abstract

The aim of the present study was to evaluate the efficacy of sewage sludge in supplying N to sunflower plants in order to substitute mineral N. Sewage sludge is an organic residue and, therefore, can contribute with several nutrients like P, S, Cu, Fe, Mn and Zn in addition to N supply. Besides improving the chemical and physical characteristics of soils, utilization of sewage sludge in agriculture can increase the lifespan of sanitary landfills. The present experiment was carried out at Sao Manuel Farm, which belongs to the School of Agronomical Sciences [Faculdade de Ciencias Agronomicas‐UNESP, Botucatu] and is located at the city of Sao Manuel. An experimental design in randomized blocks was adopted including 6 treatments and 5 replications. Treatments were as follows: T0 ‐ mineral fertilization according to bulletin 100 but without N; T1 ‐ chemical fertilization according to IAC technical bulletin 100; T2 ‐ 50% of N from sewage sludge plus 50% N from chemical fertilization; T3 ‐ 100% of N from sewage sludge; T4 ‐ 150% of N from sewage sludge; T5 ‐ 200% of N from sewage sludge. Urea was used as source of N; simple superphosphate, as source of P; potassium chloride, as source of K; and boric acid, as source of B. Each parcel consisted of 100 m2. For sunflower, the utilization of sewage sludge as a source of N led to significant increases in oil and dry-weight production.