Dynamics of water and nitrogen stress along the grapevine cycle as affected by cover cropping

Abstract

Cover cropping is developing in vineyards as it may induce numerous ecosystem services. However, soil cover also competes with grapevine for soil resources. This work aimed at evaluating both the period and intensity of the resulting water and nitrogen stress experienced by grapevine by comparing treatments with bare soil, permanent and non-permanent soil cover. The adopted stress indices were the Fraction of Transpirable Soil Water (FTSW) and the Nitrogen Nutrition Index (NNI).Cover cropping improved winter soil water refilling, but the grass transpiration during spring later led to similar water stress of grapevine among treatments. In dry years, summer water stress was not higher with non-permanent cover than with bare soil. The building of a critical nitrogen content curve for grapevine enabled to diagnose an early nitrogen stress, from budbreak to flowering, in cover cropped treatments. NNI dropped then in dry years, particularly in cover cropped treatments.The early growth limitation of grapevine observed in cover cropped treatments was the consequence of mild early nitrogen stress, which suggests that perennial nitrogen reserves were reduced because of an earlier competition with cover crop. After grapevine flowering, water appeared to be the most limiting factor for both grapevine growth and nitrogen availability.In water limited environment, nitrogen stress is highly dependant on water constraints. However, this work reveals the partial uncoupling of the dynamics of water and nitrogen stress during the grapevine cycle in water-limited cropping systems, which highlights the relevance of a co-ordinated management of water and nitrogen.