Effectiveness of inorganic and organic mulching for soil salinity and sodicity control in a grapevine orchard drip-irrigated with moderately saline waters

Soil mulching is a sensible strategy to reduce evaporation, accelerate crop development, reduce erosion and assist in weed control, but its efficiency for soil salinity control is not as well documented. The benefits of inorganic (plastic) and organic (grapevine pruning residues) mulching for soil salinity and sodicity control were quantified in a grapevine orchard (cultivars 'Autumn' Royal and 'Crimson') drip-irrigated with moderately saline waters. Soil samples were taken at the beginning and end of the 2008 and 2009 irrigation seasons in six vines of each cultivar and mulching treatment. Soil saturation extract electrical conductivity (ECe), chloride (Cl-e) and sodium adsorption ratio (SAR(e)) values increased in all treatments of both grapevines along the irrigation seasons, but the increases were much lower in the mulched than in the bare soils due to reduced evaporation losses and concomitant decreases in salt evapoconcentration. The absolute salinity and sodicity daily increases in 'Autumn' and 'Crimson' 2008 and in 'Crimson' 2009 were on the average 44% lower in the plastic and 76% lower in the organic mulched soils than in the bare soil. The greater efficiency of the organic than the plastic mulch in 'Crimson' 2009 was attributed to the leaching of salts by a precipitation of 104 mm that infiltrated the organic mulch but was intercepted by the plastic mulch. Although further work is needed to substantiate these results, the conclusion is that the plastic mulch and, particularly, the organic mulch were more efficient than the bare soil for soil salinity and sodicity control.