Effect of shallow tillage and straw mulching on soil water conservation and grapevine response

Abstract

Effects of shallow tillage and straw mulch thickness on water conservation and grapevine responses were compared to bare, untilled soil in a Sauvignon blanc/99R vineyard near Stellenbosch from 1995 to 1997. Shallow tillage to a depth of 6 cm did not conserve soil water or improve grapevine yield, growth and juice characteristics compared to bare, untilled soil. Since frequent, shallow tillage may also damage soil structure in the surface layer, it was not recommended to conserve water in vineyards. Organic mulches, which consisted of 4 t ha⁻¹, 8 t ha⁻¹ and 12 t ha⁻¹ wheat straw, reduced water losses primarily during the initial, constant-rate evaporation stage. Therefore, the water conservation effect of mulches will be more pronounced in the case of high-frequency irrigation. Cumulative water losses decreased with an increase in straw mulch thickness. Mulches were able to conserve water for at least two seasons without maintenance. Under low-frequency irrigation, mulching did not affect grapevine response positively, irrespective of mulch thickness. However, mulching can be beneficial where vineyards require frequent irrigation in coarse textured or shallow soils. Mulches can also be applied to conserve water when irrigation resources become limited during droughts, or when climate change increases evaporation losses.