No abstract

The adoption of a sustainable soil management system is essential for the steep slopes and low fertility soils still supporting rainfed olive orchards in the Mediterranean basin. The effect of the soil management on olive yield, tree nutritional status and soil fertility was studied in a rainfed olive orchard located in NE Portugal that had been managed since its earliest days as a sheep-walk. In 2001, three different soil management systems were established: Sheep-walk, in which the vegetation was managed with a flock of sheep; Tillage, where the vegetation was controlled by conventional tillage; and Glyphosate, where a glyphosate-based herbicide was applied. The soil management systems had a pronounced effect on olive yield. The accumulated olive yields between 2002 and 2011 were 187.2, 142.9 and 89.5 kg tree-1, respectively in the Glyphosate, Tillage and Sheep-walk treatments. However, the effect of soil management on tree nutritional status was not so clear. On the other hand, the pools of organic carbon and N in the soil, and also the soil available N and phosphorus (P), were found to be less in the Glyphosate and Tillage treatments in comparison with the Sheep-walk. In these soils, N appeared as a much more limiting factor for crop growth than P. In rainfed orchards, the tolerance to herbaceous vegetation appears to be a determining factor in sustainability, which regulates annual crop yields and soil fertility. The higher the tolerance to herbaceous species, the lower the olive yields, but the better are the soil fertility parameters.

a b s t r a c tA natural source of nitrogen (N) is needed to increase soil fertility in traditional olive orchards and to maintain the N nutritional status of olive trees. With this aim, we studied the introduction of legume cover crops in two olive orchards, which were converted into mulches and left on the ground as phytomass after they had been cut. The experiments were carried out in Suç ães and Qta do Carrascal, NE Portugal, from October 2009 to January 2012. In Suç ães, the ground-cover treatments were lupine (Lupinus albus L.), a mixture of 11 self-reseeding annual legume species, natural vegetation fertilized with 60 kg N hm −2 and natural vegetation not fertilized. The treatments imposed in Qta do Carrascal were lupine, hairy vetch (Vicia villosa Roth.), a mixture of 11 self-reseeding annual legumes and natural vegetation. Soil N availability in the year following the establishment of the mulches was monitored by an in situ incubation technique. Olive yields and tree nutritional status were also measured. A peak of net N mineralization was recorded early in the autumn in the plots where the legume cover crops had been grown in the last season, in comparison with the natural vegetation plot. In the next spring, soil N availability was negligible even in the plots previously cropped with legume species. The effect of the legume cover crops on soil inorganic-N availability seems to have been slight and short-lived taking into account the high amounts of N contained in the mulched phytomass. The effect of legume cover crops on olive yield and leaf N concentration was statistically significant only in few occasions. The results of these experiments recommended some caution in the management of pure legume cover crops as a mulch in olive orchards due to the reduced transfer of N from legumes to olive trees.

No abstract

The present research aimed to evaluate the water dynamics of grapevines trained in Cordon and Guyot systems by coupling sap flow and trunk diameter measurements under Mediterranean climate conditions. The study was conducted in a vineyard with Touriga-Nacional located at the Douro Valley, Portugal, during 2017. The results showed daily trunk diameter fluctuations (TDFs), with the contraction, recovery and increment phases and higher sap flow (SF) rates at earlier stages. Under harsh pedoclimatic conditions, SF was reduced and TDF flattened. Rehydration and stomatal mechanisms were mostly associated with these responses. Guyot vines showed higher changes in TDF for the same SF values, whereas the TDFs of Cordon vines remained practically unchanged over maturation. Guyot vines generally showed increased values of cumulative increment and maximum daily trunk shrinkage. Although Guyot vines had a similar leaf area index (LAI), they showed higher SF/LAI ratios than Cordon vines. These results highlight the effect of the shorter length of the hydraulic pathways of the Guyot training system, in contrast to the higher trunk and the permanent horizontal branch (cordon) of the Cordon training system, indicating good adaptation to local pedoclimatic conditions. The study pointed to the complementary use of both techniques in the evaluation of grapevine water dynamics.