Manejo da irrigação por alagamento e a toxidez por ferro no arroz cultivado em casa de vegetação.

• Main Author: Schmidt, Fabiana
• Publication Date: 2009
• Format: Master thesis
• Language: por
• Source: Repositório Institucional da UFPel - Guaiaca
• Download full: http://repositorio.ufpel.edu.br/handle/ri/2450
• topic: Arroz; Solos alagados; Toxidez; Ferro; Rice; Flooded soil; Toxicity; Iron; CNPQ::CIENCIAS AGRARIAS::AGRONOMIA

Iron toxicity is one of the most important abiotic stresses limiting rice production in lowland systems. Soil flooding affects the gas exchange processes with the atmosphere promoting oxi-reduction conditions in rice fields. The oxi-reduction state of the soil is influenced by anaerobic microorganism activities, which is affected by water management. With the objective of evaluating the effect of different water management systems on iron reduction dynamics in flooded Albaqualf Soil and to iron toxicity symptoms in irrigated rice plants. The experiment was performed in the greenhouse using a randomized complete block design with four replications. The water management treatments were: 1. Beginning of flooding in the stage V2-V3 (Condition 1); 2. Beginning of flooding in the stage V6-V7 (Condition 2); 3. Condition 1 and drainage in the stage V10-V11; 4. Condition 2 and drainage in the stage V10- V11 and 5. Condition 1 and drainages in the stage V8-V9 and V10-V11. Was sampled the soil solution weekly at 17, 24, 31, 41, 48, 55, 63 and 70 days after the emergence of the rice plants. In the soil solution the Eh, pH, and the concentration of Fe, Mn, Ca, Mg, P and K were evaluated. In the rice plants the shoot dry matter and the concentrations of the following nutrients: N, K, P, Ca, Mg, Fe, Mn, Cu and Zn, at 42 and 70 days after the emergence were evaluated. Iron toxicity symptoms were assessed at 50, 60 and 70 days after the emergence of the rice plants. The results were subjected to analysis of variance, Duncan s Test at 5% probability and correlation analysis. The delay of the start of the water flooding to stage V6-V7 kept the redox potential of soil solution higher what promoted less Fe available and moved the iron release peak to later stages of plant growth. Drainages during the rice growth cycle promoted soil re-oxidation leading to an increase of redox values due to the decrease of Fe concentration in the soil solution as consequence of oxidation of Fe compounds previously reduced in the flooded soil. This water management procedure was effective in promoting lower shoot Fe levels at V10-V11stage as well as at maturity stages. Also, it atenuated the toxicity symptoms and/or delayed it occurrence to later stages. Two drainage events during the rice growth cycle produced the highest shoot dry matter yield at plant maturity. Highest Fe in soil solution was correlated with higher increases in Fe concentrations in shoot, higher percentage of leaves showing iron toxicity symptoms and decrease of rice shoot dry matter. The Fe concentrations in the rice plants were correlated with leaf iron toxicity symptoms only at 41 days and were not correlated with shoot dry matter yield. At rice maturity stage the increase in percentage of leaves showing iron toxicity symptoms was correlated with shoot dry matter yield decreases. Keywords: Rice. Flooded soil. Toxicity. Iron.