THE USE OF OLIVE MILL EFFLUENTS (MARGINES) AS SOIL CONDITIONER MULCH TO REDUCE EVAPORATION LOSSES

This study evaluated the efficiency of waste by-products of olive oil extraction (called ''margines'') as a soil conditioner. Because of the adhesive, hydrophobic, and fertility properties of margines, their di rect effect on soil aggregation and on the changes of hydrodynamic soi l characteristics were assessed. The wet sieving technique and rainfal l simulation were used to determine the optimal application rate of th e soil conditioner on a loamy sand. The efficiency in reducing evapora tion losses of incorporation and surface application treatments with s traw mulch (450 g cm(-2)) and a bare untreated soil surface under labo ratory-controlled evaporativity of 10 mm day(-1) were compared. Moistu re content was determined by means of time domain reflectometry. It wa s concluded that the application of a straw mulch was very efficient i n controlling evaporation only during the initial stage of evaporation . A surface application of margines is not as effective in reducing ev aporation as incorporating them. The latter application reduced the ev aporation loss by almost 30%. When applying the models of Groenevelt e t al, [Soil Technol. 2 (1989) 279-285] and van Wesemael et al. [Phys. Chem. Earth. 20 (1995) 293-299] the two phases in the evaporation proc ess were identified. The drying coefficient k(d) introduced by Groenev elt et al. [ibid,] describes the second phase of the evaporation proce ss, and the proposed soil boundary condition coefficient k(b) by Groen evelt et al. [ibid.] and van Wesemael et al. [ibid,] describes the fir st phase as a function of the soil surface condition. (C) 1998 Elsevie r Science B.V. All rights reserved.