Towards a near-soilless culture for woody perennial crops in open field conditions

Abstract

Abstract Increasing water-use efficiency (WUE) is mandatory for more sustainable agricultural land use. Here we studied during three consecutive years in a nectarine (Prunus persica L.) orchard the effects of placing 2 × 40 L coconut fiber substrate (S) bags per tree on the agronomic performance and WUE. Additionally, there were two regimes of watering, control (C), fulfilling 100% of the estimated crop evapotranspiration (ETc) and a deficit (D) irrigation treatment, replacing the 65% of the ETc. Root colonization of the substrate, changes in the soil and substrate water content and temperature, tree water status (midday stem water potential), shoot growth (trunk diameter and tree volume), fruit yield and fruit quality compounds, were determined. Coconut substrate was colonized by the roots after two months from its installation, and after three years root dry weight in the substrate averaged 172 and 155 g per tree for the control and deficit irrigation treatments, respectively. During the first year, tree growth was enhanced in the C irrigation, while freezing temperatures during fruit set almost totally removed all fruits. In the second year, probably the abundant rainfall disguised the effect of the substrate on the yield parameters. However, this year and the next, deficit irrigation reduced fruit mean weight and delayed fruit harvest. In the third year, the substrate in the deficit irrigation treatment had a positive effect on fruit yield by increasing the number of fruits per tree in comparisons with deficit irrigation trees without substrate. The combination of deficit irrigation and substrate increased the WUE over the rest of the treatments but with no clear improvements in the tree water status. The results suggest that nectarine trees with deficit irrigation and substrate could be benefiting from a more efficient use of nutrients that further increases fruit set or prevent fruit drop.