Plant trait analysis to determine effective annual cover crops for Spanish orchards

This paper investigates the use of plant trait analysis on cover crop species, and the impact selected species had on soil chemistry in a Spanish olive orchard. Farmers with hillside orchards in Spain frequently remove vegetation between tree rows due to concerns about water competition in the semi-arid environment. However, this increases the vulnerability of the soil to water erosion. Despite research showing that annual cover crops control soil loss, there has been little uptake of this form of management by farmers.

Ten species, native to southern Spain which had previously been used in cover crop experiments, and for which the seed was low cost, were assessed with plant trait analysis. Above and below ground traits, including specific leaf area, total biomass, root diameter and root volume, were examined to indicate the potential of the plants to reduce splash erosion, runoff and soil detachment. Four of the species were then selected and used in monocultures and mixes in an olive orchard set up in collaboration with CSIC in Cordoba. Soil moisture, rainfall, temperature and soil cover data was collected. Chemical analysis of plant and soil samples is to take place in January 2021.

Brachypodium distachyon, Calendula arvensis, Medicago sativa and Medicago truncatula had the most potential as cover crop species. In the field, the treatment with the greatest number of species (two grasses, one legume and one forb) had the highest mean soil cover at 78 ± 16%. It is hypothesised that the plots in which the greatest cover was established would show the greatest change in soil chemistry and that, where the legume was planted there will be higher nitrogen in the soil.

This presentation will outline the plant traits analysed, the outcomes of this analysis and the impact selected plants had on plant and soil chemistry in the field.