Abstract

ALEXANDRE, C.; ANDRADE, J.  and  AFONSO, T.. Soil management and vegetation control effects on soil water content in olive orchards in Alentejo . Rev. de Ciências Agrárias [online]. 2007, vol.30, n.2, pp.217-232. ISSN 0871-018X.

This paper compares results of soil water content, measured between January of 2004 and April of 2005, under 3 different methods of soil management and weed control in young olive orchards: alfalfa cover, Medicago spp. (L), conventional tillage (M), and no tillage (N). This study is being carried out in trials of olive orchards set up near Moura, Alentejo. The plots used for soil water measurements are located on a slope with 4-5% gradient with a Calcaric-Vertic Cambisol (Chromic), according to the WRBSR. Soil water content was measured with three different methods and frequencies: irregular, by the gravimetric method, mainly for the 0-10 cm layer; periodic, approximately twice a month, with a probe PR1 (Delta-T)* from 0 to 40 cm depth, and continuously, with the same probes and depths. Considering the limitations of PR1 probes for clayey soils, results are discussed comparatively. Alfalfa treatment reveals a quicker decrease of the soil water content for the layer 0 to 20 cm on periods of greater plant growth, and also during the winter of 2005 (with very low minimum temperatures, high daily thermal amplitudes and extreme dryness). Conventional tillage shows some signs of greater discontinuity in soil water content profile between 10-20 cm and 20-30 cm layers, suggesting worse drainage around 20 cm depth. Soil under conventional tillage was kept bare during the summer of 2004 and showed greater variation on soil water content between 0 and 20 cm. This difference might be the result of a greater amount of intercepted rain, trapped on the mulch residues at soil surface, on the alfalfa and no tillage treatments. The soil under no tillage shows a more homogeneous soil water profile: no tillage allows a greater variation of soil water content under 20 cm depth than the conventional tillage, and weed control makes a lower soil water loss above 20 cm depth than the alfalfa cover. (^* Mention made only for information).

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