Green manuring in viticulture: impact of cover crop species and way of destruction on nitrogen supply of the grapevine

Abstract

Green manures are plants grown to improve soil fertility. This technique which is implemented in many cropping systems such as field crops or vegetables is still few studied in viticulture. On the one side, green manure cover crops are likely to have several beneficial effects on soil. On the other side, the management of the crop in terms of species and period shall allow optimal control of nitrogen available for the vine.

Our study, carried out since 2011 in south-west of France, focused on two key factors to manage the release of the green manure nitrogen in the soil: the research of the most suitable type of cover (Poaceae, Brassicaceae, Fabaceae mixes) and the method of destruction – destruction by rolling and destruction by grinding followed by incorporation into the soil have been compared.

Our measurements focused on i) evolution of the stock of mineral nitrogen in the soil ii) agronomic parameters of the vine: nitrogen supply, yield, vigor iii) development of winter annual cover crop: aerial biomass and carbon and total nitrogen content.

Among the studied species, our results highlighted the good behavior of bell bean (Vicia faba) as winter green manure through its high biomass production in late sowing conditions. Even if the dynamics of mineral nitrogen in the soil depended on the vintage conditions, we recorded a greater release of mineral nitrogen in the soil with green manures; this effect was majored when the crop was incorporated into the soil. From an agronomical point of view, the practice had low incidence on yields but allowed a significant increase in the nitrogen content of the must (up to 65%).

Green manures seem to be a very promising technique in viticulture to reconcile maintenance of soil without herbicides and improved nitrogen nutrition of the vine.