Evaluation of schist and scoria in the nutrition and production of tomato and the effects on the soil chemical and biological attributes

Author(s)

Hamilton Seron Pereira

• Document type: Doctoral Thesis
• Press: Piracicaba.
• Institution: Universidade de São Paulo (USP). Escola Superior de Agricultura Luiz de Queiroz (ESALA/BC)
• Defense date: 1999-08-26
• Advisor: Godofredo Cesar Vitti

Abstract

Some processes in the industry generate residues, many of these can be re-utilized, instead of being deposited in places that could cause problems, contaminate or cause changes in the environment. Schist is a silty-clayey rock of the lratí formation, with a high content of organic matter, that when heated can produce oil, gas and sulfur. ActualIy, in the exploitation unit of schist, after the extraction of oil, gas and sulfur, the residue is discarded reaching an amount of 6000 Mg day -1. Another residue that is not re-utilized are the scorias, their corrective action has already being demonstrated. In the process for the obtention of the gusa iron, 300kg of scorias are produced by iron Mg. To evaluate the re-utilization of these residues in agriculture, two experiments were performed with a randon complete block desing growing tomato on Alfisols in greenhouse conditions (plasticultura). Pour doses of schist were used in the experiments (3,6, 9 and 12 Mg ha-1), two siderurgy high oven scorias (Mannesman and Dedini) with a doses of 6 Mg ha-l and thermophosphate, that uses scorias in its fabrication process, with a doses of 2.5 Mg ha-1. The experiments had eight treatments including the control, with four repetitions. Ali the treatments received NPK mineral fertilization, including the controI. The nutritional state and production of tomato were evaluated. Due to the high concentration of silicates in the residue, the addition of silicium to the soil and crop was evaluated; some chemical and biological attributes were evaluated. The results showed that the scorias were efficient in the acidity correction while schist did not alter this attribute. Schist and scorias increased the soil and plant siIicium content, this increase of silicium in the soil increased the availabily of phosphorus, due to the direct competition for the adsorption sites between silicium and phosphorus. Schist increased the soil and plant sulfur content, being efficient in the supply of this element to the crop. High levels of heavy metaIs were not verified in soils and in the plants caused by the application of these treatments. The level remained below those considered criticaI for the soil and that could harm the environment. The soil’s bacterial population was increased with the application of Mannesman scoria while schist increased the fungaI population, but environmental problems not were identified, such as the chemical contamination by heavy metaIs, as the diminishing of the soil biological activity, as well as the productivity decrease as a function of the applied treatments. The products used in these experiments and in the suggested doses can perfectly be used in agriculture, as correctives or as soil conditioners (AU)