Agricultural use of compost under different irrigation strategies in a hedgerow olive grove under Mediterranean conditions. A comparison with traditional systems

Abstract

Abstract. Soil and water efficient management are key factors to ensure olive sustainable production. The use of compost based on olive waste (alperujo) as fertilizer could enhance ecosystem services while the need to transition to a zero waste circular economy is achieved. The present work includes a comparative study of the effect of alperujo compost (AC) vs inorganic fertilization under different management systems: an intensive traditional adult olive grove under rainfed conditions and a young hedgerow olive system, in which a factorial test of tree irrigation regimes (full, deficit and no irrigation) is implemented as well. At the hedgerow plots, the addition of AC and soil sampling time greatly impacted soil chemical parameters and to a lesser extent, enzymatic activities whereas irrigation regimes did not exert a mark influence. In the traditional rainfed system, the addition of AC proved to be an efficient tool for carbon sequestration. The first soil sampling revealed a clear stoichiometric relationship between soil organic matter (SOM) and the NPK contents at both systems whereas the correlations were weak and scarce in the second sampling at the hedgerow plots. This fact was related to a decay of the compost effect. Compost in combination with irrigation tended to trigger a certain priming effect on the native SOM with time since the carbon stocks were reduced between 6–38 % from one sampling to the other in the hedgerow system depending on the irrigation intensity. However, the deficit irrigation caused a less intense reduction of the SOM and essential nutrients representing the best alternative to maximize the agronomics effects of the compost under a water-saving strategy. Recurrent application of compost would be necessary to maintain soil quality, especially with high tree densities. The combined management of AC and the deficit irrigation proved to be an efficient tool toward a zero waste circular economy and a water conservation strategy.