Resumo

BARTOLO, Inês; FERNANDES, Rui  e  SEMPITERNO, Cristina. Agricultural valorization of sewage sludge: phosphorus availability. Rev. de Ciências Agrárias [online]. 2017, vol.40, n.3, pp.497-505. ISSN 0871-018X.  https://doi.org/10.19084/RCA17080.

Sewage sludge from treatment plant are rich in organic matter and nutrients, which are essential to the growth and development of plants. When properly applied to the soil, they contribute to fertilization of crops, thus saving the use of chemical fertilizers. In order to contribute to a better understanding of sludge phosphorus supply to the soil, a pot trial was installed using maize as a test plant. For this purpose, the experiment was arranged into randomized complete block design, with three replicates, and thirteen experimental treatments as follows: (i) a control treatment without phosphorus supply; (ii) four treatments with increasing levels of phosphorus supplied through sludge; (iii) four treatments with increasing levels of phosphorous supplied through calcium phosphate and (iv) four treatments with the same levels of phosphorus but supplied through sludge and calcium phosphate. The biomass production was higher with the treatments that received the higher amounts of phosphorus supplied through sludge and calcium phosphate. The supply of the maximum amount of sludge (equivalent to 120 t ha^-1) caused a decrease of the biomass production and led to a lower use of phosphorus by the plants. Therefore, it is necessary to establish maximum limits for the quantities of sludge to be supplied to the agricultural soils. In relation to the production of biomass and the apparent recovery of phosphorus, the good results show that the combination of sludge and calcium phosphate will be able to make possible an economy of these fertilizers. Even though sludge cannot totally replace phosphate fertilizers, it can be used as a partial substitute.

Palavras-chave : phosphorus; sewage sludge; recovery; removal.

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