Filipe Selau Carlos

ABSORÇÃO DE NUTRIENTES E CRESCIMENTO DO ARROZ COM SUPRIMENTO COMBINADO DE AMÔNIO E NITRATO

Rice is classified as an ammonium (NH4+)- tolerant plant due the predominance of this ion in flooded soils. However, in the oxygenated zones of flooded soil and in the rice rhizosphere, nitrate (NO3-) can be formed and become an important nitrogen (N) source for the crop. This experiment was carried out to evaluate the effect of different ammonium:nitrate proportions on rice development in nutrient solution. The experiment was carried out in a greenhouse, from January until February 2008 in a nutrient solution with the following NH4+: NO3- proportions: 100:0, 75:25; 50:50; 25:75 and 0:100, at 5.0 mmol L-1 N. The genotype IRGA 417 was used and the biomass production, the nitrogen, calcium, magnesium and potassium contents in tissue and xylem sap were evaluated. The presence of ammonium at the proportions 100:0 and 75:25 resulted in plant toxicity, as well as for nitrate at the proportions 25:75 and 0:100. The combined supply of ammonium and nitrate increased biomass production in relation to solely NH4+ or NO3- supply. Ammonium in solution affected negatively Ca and Mg, whereas no effect was observed on N or K tissue contents. However, in the xylem sap, both K, Ca and Mg contents were affected by ammonium. The higher total absorbed quantities of N, K, Ca, and Mg and better rice development indicated that the combined supply results in higher nutrient absorption efficiency than solely ammonium or nitrate supply.

Treated Industrial Wastewater Effects on Chemical Constitution Maize Biomass, Physicochemical Soil Properties, and Economic Balance

ABSTRACT Irrigation with treated wastewaters can improve nutrient levels and yield of crops planted on degraded soils. This study evaluated how irrigation with treated industrial wastewater affected biomass production and nutrition of maize plants and physio-chemical properties of a degraded soil. The experiment was conducted in a greenhouse using PVC columns. Treatments consisted of 8 treatments irrigated with clean water and increasing doses of N and P, and 8 treatments with 4 proportions of wastewater irrigation (25%, 50%, 75% and 100% v/v). In general, maize biomass did not differ between irrigation water sources. Differences were largely associated with N nutrition. We observed increases in concentrations of N, P, K, S, Mn, Na, Cu, and Zn in tissue of maize under irrigation with wastewater. The addition of treated wastewater increased the P and Na concentrations, and EC values in the soil without affecting clay dispersion in water. An associated economic analysis indicated that wastewater irrigation would not be economically feasible without including environmental benefits. In southern Brazil, the proportion of irrigation water that is wastewater should not exceed 50%.

Heavy Metals and Nutrients Uptake by Medicinal Plants Cultivated on Multi-metal Contaminated Soil Samples from an Abandoned Gold Ore Processing Site

Heavy metal extraction from soils is one of the functions of plants which is widely studied and applied worldwide. However, little is known to what extent medicinal plants can accumulate these metals and cause problems to human health. This study aimed to evaluate the accumulation of heavy metal/loid in plant tissues, nutritional imbalance, and the effect of heavy metal concentrations in soil on the medicinal plants. The experiment was conducted in a factorial scheme with three contaminated soil samples and a soil sample from an uncontaminated field and three medicinal species: Cynara scolymus, Ocimum basilicum, and Rosmarinus officinalis. The heavy metal content in the biomass increased with increasing soil samples concentration. Biomass production, nutritional imbalance by nutrients did not show consistent results according to soil contamination criteria and are not good indicators of heavy metals presence in plant tissues, since they did not allow predicting the presence of metal in the plants, due to the different behavior of elements and plant species. There was a high concentration of Cd, Cr, Pb, and As and micronutrients Fe, Zn, and Cu in the plant tissues, above the limits recommended by the World Health Organization. Therefore, as the components of C. scolymus, O. basilicum, and R. officinaliss are used to prepare teas, condiments, or consumed raw, coupled with the ability of such species to concentrate toxic metals, the continued use of these plant products containing these metals can pose a potential health concern.

Impact of Treated Industrial Effluent on Physical and Chemical Properties of Three Subtropical Soils and Millet Nutrition

ABSTRACT The use of treated industrial effluents to irrigate plants is an alternative, because of nutrients that can increase yield of the agricultural crops. This study was conducted to determine irrigation with treated effluent and gypsum application, which changes the chemical and physical characteristics of soils and the growth and nutrition of millet (Pennisetum glaucum). Thus, an experiment was conducted on PVC columns with three soil classes, Typic Hapludox, Typic Hapludult, and Arenic Hapludult. Nutrient and Na+ concentrations in the millet biomass reflected concentrations of elements in the effluent and soil. In the control, low N levels were found in the biomass, while higher leaf N concentrations were observed, due to irrigation with treated effluent. In the short term, irrigation with treated industrial effluent by controlled application could be an alternative and a complementary source of nutrients for plants, reducing the volume of nutrients and organic materials discharged into water bodies.

Iron oxidation on the surface of adventitious roots and its relation to aerenchyma formation in rice genotypes

Establishment of the water layer in an irrigated rice crop leads to consumption of free oxygen in the soil which enters in a chemical reduction process mediated by anaerobic microorganisms, changing the crop environment. To maintain optimal growth in an environment without O2, rice plants develop pore spaces (aerenchyma) that allow O2 transport from air to the roots. Carrying capacity is determined by the rice genome and it may vary among cultivars. Plants that have higher capacity for formation of aerenchyma should theoretically carry more O2 to the roots. However, part of the O2 that reaches the roots is lost due to permeability of the roots and the O2 gradient created between the soil and roots. The O2 that is lost to the outside medium can react with chemically reduced elements present in the soil; one of them is iron, which reacts with oxygen and forms an iron plaque on the outer root surface. Therefore, evaluation of the iron plaque and of the formation of pore spaces on the root can serve as a parameter to differentiate rice cultivars in regard to the volume of O2 transported via aerenchyma. An experiment was thus carried out in a greenhouse with the aim of comparing aerenchyma and iron plaque formation in 13 rice cultivars grown in flooded soils to their formation under growing conditions similar to a normal field, without free oxygen. The results indicated significant differences in the volume of pore spaces in the roots among cultivars and along the root segment in each cultivar, indicating that under flooded conditions the genetic potential of the plant is crucial in induction of cell death and formation of aerenchyma in response to lack of O2. In addition, the amount of Fe accumulated on the root surface was different among genotypes and along the roots. Thus, we concluded that the rice genotypes exhibit different responses for aerenchyma formation, oxygen release by the roots and iron plaque formation, and that there is a direct relationship between porosity and the amount of iron oxidized on the root surface.