Effect of permanent ground cover on agronomic properties and soil fertility in an organic peach orchard

In conventional orchards, weeds on the raw are mainly controlled with chemical herbicides because of their efficiency, their low cost and ease of use. The most common method in organic orchard to eliminate weeds on the raw consists of tillage operations. However, some drawbacks of these mechanical methods have been demonstrated: (1) the energetic cost (non-renewable energy) is high, (2) this method is time-consuming, (3) tillage interferes with the development of superficial roots and can hurt the trunk, (4) the physical, chemical and biological properties of the soil can be disturb and (5) erosion and runoff potentially increase. Cover crops are interesting alternatives to manage ground cover but the effect on the agronomic properties and the soil fertility of these methods should be assessed. This study is included in the national program “Casdar SolAB” supported by the French Ministry of Agriculture. The effect of a White Clover crop versus tillage practice on the tree raw was assessed in an irrigated organic Peach orchard. White Clover was sowed in 2004. Soil parameters (water and nutrients availability, soil porosity, root density, earthworms density, soil profile) and agronomic parameters (yield, fruit quality, pests and diseases damages) were recorded since 2004. A 50% decrease of the organic fertilizer supply in the White Clover treatment has not affected yield and fruit quality from 2005 to 2009. It suggests this cover crop is well adapted to our pedoclimatic conditions without exerting a significant competitive effect. Root density is higher in the superficial layers of the soil in the White Clover treatment. Simplified Beerkan test used to assess soil porosity has also shown that soil porosity is higher in this treatment. No vole damage was observed in the plot