Potencial do fertilizante orgânico classe D no cultivo inicial de eucalipto
Afáz, Daniela Cristina de Souza
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Organic fertilizers are increasingly identified as an alternative route for agriculture, acting as a conditioner of soil physical, chemical and biological properties, and as a source of nutrients for crops. Therefore, this study evaluated the feasibility of use for a “class D” organic fertilizer obtained from a sewage treatment plant, as an alternative fertilizer for eucalyptus cultivation. The experiment was conducted in Agricultural Science Center-UFSCar, in Araras, SP, in a greenhouse. Cultivation occurred from November 2014 to January 2015, totalizing 75 days. We adopted a complete randomized design, with five treatments and seven repetitions, with plants cultivated in 11 L pots. The tests considered a testimony treatment with no fertilization (T1), three treatments (T2, T3, T4) with organic fertilizer addition (25%, 50% and 75% of the pot volume) and treatment (T5) with conventional fertilizers, all in sandy soil. Drip irrigation three times a day was used with a flow rate of 1 L h-1. We measured plant height and soil electrical conductivity every two weeks. Relative growth rate (RGR), plant dry mass and leaf micro and macro nutrients concentration were evaluated at the end of the experiment. Plant dry mass, relative growth rate and nutritional data were submitted to analysis of variance and the means compared by Tukey test at 5% probability. We found no significant differences in plant height. Treatments T3 and T5 had a greater relative growth rate (p < 0.01). Plants from the fertilized treatments had more leaf macro and micronutrients when compared to the testimony and, in general, leaf nutrient values were within reference values for eucalyptus growth. Soil electrical conductivity increased with the increase in the percentage of organic fertilizer in the soil, what is explained by its content of salts charges. However, the organic fertilizer did not promote salinity to plants. Thus, we conclude that the “class D” organic fertilizer we tested is a potential substitute of conventional mineral fertilization for eucalyptus cultivation.