Abstract

SEMPITERNO, Cristina; FERNANDES, Rui  and  BARTOLO, Inês. Residual phosphorus effects on sequential crops by agricultural valorization of sewage sludge. Rev. de Ciências Agrárias [online]. 2020, vol.43, n.3, pp.24-45.  Epub Sep 30, 2020. ISSN 0871-018X.  https://doi.org/10.19084/rca.20394.

The main objective of this study was to evaluate the availability of residual phosphorus delivered by the application of sewage sludge to the soil using a two crops sequence, maize (Zea mays L.) followed by ryegrass (Lollium multiflorum L). The experiment was carried out in pots in a conditioned environment. A randomized complete block design was used, with three replicates, and thirteen experimental treatments as follows: (i) control, without phosphorus supply; (ii) four treatments with increasing levels of phosphorus supplied through sewage sludge; (iii) four treatments with increasing levels of phosphorus supplied through calcium phosphate and (iv) four treatments with the same levels of phosphorus but supplied through sludge plus calcium phosphate. The observed results show that the first crop (maize) reduced the biomass by maximum addition of sludge (equivalent to 120 t / ha), whereas a significant increase was observed for total ryegrass biomass. Apparent phosphorus recovery, meaning the percentage of absorbed P (in relation to the applied quantities) , was much higher in the second crop in all experimental treatments, showing the potential residual effect of this element in the soil.

Keywords : residual phosphorus; sewage sludge; apparent recovery.

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