Influence of cover cropping on water uptake dynamics in an irrigated Mediterranean vineyard

As a result of its physiological characteristics, vine's yield and quality responses are greatly affected by water availability in the soil. Knowledge about water uptake of grapevines in pedoclimatic conditions of high water availability is essential when considering the increasing use of irrigation in a previously rainfed crop. We studied the water uptake of irrigated grapevines under different soil covers. The study was carried out over 2 years in southern Portugal, a Mediterranean climate region, in ‘Aragonez’ grapevines planted in Vertisols. A cover crop was sown in half the area while maintaining the permanent resident vegetation in the remaining area. Five levels of annual irrigation supply were applied: 200, 150, 100 and 50 mm, and no irrigation. Soil moisture was monitored every 2 or 3 weeks, and weekly after the start of irrigation. Results show that water uptake in the interrows did not cease after the beginning of irrigation. Water uptake by the vines occurred to depths of approximately 3 m, hence 7.5 times greater than the cover crop root system depth. Results suggest that over time, the presence of the cover crop forces the vine root system, mainly its thinner roots, to seek water in increasingly deeper soil compartments.