Caracterização físico-química do lodo seco da parboilização de arroz e sua utilização na agricultura

Abstract

The rice parboiling residues disposition on the agriculture can represent a less aggressive alternative to the environment, when it comes to nutrient recycling. The parboiling is a hydrothermal process, in which the rice is submitted to a soaking period, followed by autoclaving and drying, causing the movement of nutrients within the rice rind into the grain interior, along with the lixiviation of several compounds into the water used for the soaking of grains. The silt obtained in this process presents high rates of organic compounds, nitrogen and phosphor, of which, if used, could avoid environmental problems such as the water sources eutrophication. The objective of this study was to characterize the chemical and physical of the rice parbolization dry silt (RS-UASB), and thus, evaluate its effects when applied on the soil, regarding the plants growth and nutrition. The RS-UASB showed a pH of 7,3, a neutralization value of 55% measured by titration, and 67,3% measured by incubation. It also demonstrated high levels of Ca (25%), P (25%), Na (1,2%) and K (0,97%). X-ray diffraction showed percentage crystallinity around 62%, with calcite as the main compound. Its density was of 0,77 g cm-3. Except by phosphor, all detected elements were below the levels permitted by FEPAM-RS to effluents discard. On the experiment carried in greenhouse, maintained for a period of 60 days, it was utilized the dosages of 16, 32, 48 e 64 Mg ha-1 from RS-UASB. The application of these residues to the Planossoil soil, raised the respective pH. With raising dosages of such residues, until values correspondent to 64 Mg h-1, it was observed the raising of the Oat (Avena sativa L.) dry matter, and increasing absorption of total N , P , K , Ca , Mg , Fe , Mn , Cu and Zn by the plants. The application of dry silt originated from the rice parboiling has potential of being used as a fertilizer on the soil.