Compressibility, penetration resistance and least limiting water range of a Yellow Ultisol under sugarcane in the Coastal Tablelands of Alagoas State

The intensive traffic of agricultural machinery of cultivation and harvesting operations of sugarcane can promote soil compaction and affect crop yield and longevity. One of the ways to evaluate soil degradation due to compaction is by analyses of soil compressibility and least limiting water range. The objective of this study was to evaluate the effect of sugarcane cultivation on pre-compaction pressure (sp), laboratory-determined soil penetration resistance (LPS) and on the least limiting water range (LLWR) of a cohesive Yellow Ultisol of the coastal tablelands of Alagoas. The study was conducted on the Fazenda Progresso, of the Usina Coruripe, where five sugarcane areas were selected, representing different use periods and crop systems: four years under winter cropping (4 year W), 14 years under winter cropping (14 year W), 14 years under summer cropping (14 year S), thirty years under winter cropping (30 year W), and 30 years under summer cropping (30 year S). A native subperennial forest fragment (Forest) was also included in this study as a reference area. To determine the effect of sugarcane cultivation on soil compaction, sp, LPS and LLWR were determined in soil samples from the layers 00,20 m, 0,200,40 m and 0,400,60 m, corresponding to the horizons A (Forest) or Ap (agricultural areas), AB and Bt. Sugarcane cultivation increased the σp and LPS of the Ap, AB and Bt horizons of the Yellow Ultisol, however, in the Ap horizon of the soil of the agricultural areas the LPS did not reach the value considered critical for root development, and the LLWR was higher than in the surface horizon of native forest. The mechanized operations for sugarcane cultivation increased LPS to critical levels for root development, even at moisture contents near field capacity, which decreased LLWR of AB and Bt horizons in the agricultural areas. Pre-compaction pressure can be used as an indicator of load support capacity in the strategic planning of machinery operations in sugarcane fields, in order to avoid further soil compaction in the subsurface horizons of cohesive Yellow Ultisol.

Soil compaction; pre-compaction pressure; soil water behavior

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