Soil slope and texture as factors of phosphorus exportation from pasture areas receiving pig slurry

D. J. Dall'Orsoletta, L. C. Gatiboni, G. L. Mumbach, D. E. Schmitt, G. Boitt, T. J. Smyth

Research output: Contribution to journalArticleResearchpeer-review

Abstract

Phosphorus (P) loss from agricultural areas to waterbodies is a worldwide concern. However, the effect of soil source and transport factors, such as clay (C) content and slope (S), on the magnitude of the P transport in Brazilian subtropical soils is still understudied. The objectives of this study were i) to quantify the loss of P fractions by runoff in areas receiving pig slurry application and with variations in S and C content; ii) propose an environmental critical limit model of P (P-threshold) for Brazilian subtropical soils. Thus, two series of experiments were conducted from 2016 to 2018, one under a Nitisol with 642 g kg−1 of C and another under a Cambisol with 225 g kg−1 of C. The treatments were four P rates (0, 56, 112 and 224 kg P ha−1 year−1) superficially applied as pig slurry, on Tifton (Cynodon sp) pasture, and three S (10, 20 and 30% in the Nitisol and 15, 25 and 35% in Cambisol). P losses increased in both soils as the S and P rates rose. The Nitisol showed P losses three times higher than the Cambisol. Soil S above 25% promotes P losses at a rate three times higher than in soil below this limit. Therefore, we propose a P-threshold model for Mehlich-1 extractable P levels for Brazilian subtropical soils as: “P-threshold = (42.287 + C) − (0.230 S + 0.0123 C S)” in soils with a S ≤ 25% and “P-threshold = (42.287 + C) − (−0.437 S + 0.039 C S)” in soils with a S >25%, where both C and S are shown in percentage. The soil clay content and slope are aggravating factors to the P transfer process, thus must be considered in suitable models to predict the P losses risk.

Original languageEnglish
Article number144004
JournalScience of the Total Environment
Volume761
DOIs
Publication statusPublished - 20 Mar 2021

Keywords

  • Erosion
  • Phosphorus losses
  • Slope
  • Soil texture

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