Modelling the impacts of cover crop management strategies on the water use, carbon exchange and yield of olive orchards

Abstract

Cover crops have long been proposed as an alternative soil management for minimizing erosion rates in olive stands while providing additional ecosystem services. However, the trade-off between these benefits and the competition for water with the trees makes the definition of optimal management practices a challenging task in semiarid climates. This work presents an improved version of OliveCan, a process-based simulation model of olive orchards that now can simulate the main impacts of cover crops on the water and carbon balances of olive orchards. Albeit simple in its formulation, the new model components were developed to deal with different cover crop management strategies. Examples are presented for simulation runs of a traditional olive orchard in the conditions of southern Spain, evaluating the effects of different widths for the strip occupied by the cover crop (Fcc) and two contrasting mowing dates. Results revealed that high Fcc resulted in lower olive yields, but only when mowing was applied at the end of spring. In this regard, late mowing and high Fcc was associated with lower soil water content from spring to summer, coinciding with olive flowering and the earlier stages of fruit growth. Fcc was also negatively correlated with surface runoff irrespective of the mowing date. On the other hand, net ecosystem productivity (NEP) was substantially affected by both Fcc and mowing date. Further simulations under future climate scenarios comparing the same management alternatives are also presented, showing substantial yield reductions by the end of the century and minor or negligible changes in NEP and seasonal runoff.