Irrigation as an effective way to offset competition from a permanent cover crop in a Mediterranean vineyard

Abstract

Environmental benefits of permanent cover crop in vineyard are well known. Nevertheless, permanent cover cropping is quite rare in French Mediterranean vineyards, because there is a risk of severe drought during summer, and consequently yield losses. Over the past few years, irrigation has developed in this area, offering new possibilities for better control of grapevine water status in cover cropped vineyards. The aim of this experiment was to study the effects of irrigation, combined or not with nitrate fertilization, in order to compensate for the competition of a permanent cover crop in the inter-row. The experiment was carried out in a Shiraz commercial vineyard, located near Nîmes (Southern France). The experiment was designed to compare cover cropped grapevines with these different treatments: (i) no inputs, (ii) with irrigation, (iii) with nitrate fertilization, (iv) with both irrigation and nitrate fertilization, and (v) a reference on bare soil. Monitoring (water and nitrogen status of grapevine, yield components) took place from 2010 to 2013. Since 2011, cover crops have led to significant yield losses compared to bare soil treatment (-29% on average). Nitrate fertilization used alone did not improve grapevine yields. Irrigation increased grapevine yields by +10% for irrigation alone and by +19% for both irrigated and fertilized treatment. Despite these improvements, yields from cover cropped grapevine remained below yields from bare soils. Water availability seems to be the main parameter to monitor for managing the competition with permanent cover crops in Mediterranean vineyards.