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- Effect of ground cover on soil carbon storage in a citrus orchard: challenges and preliminary results.Publication . Reis, Adélia; Duarte, Beatriz; Duarte, AmilcarFruit tree crops, as a relevant agricultural sector, have great importance in the sequestration of atmospheric carbon and its stock in the soil. A vast area of citrus orchards is found in the Mediterranean region, an area prone to soil degradation and desertification. Adoption of sustainable agricultural practices, such as permanent soil cover in orchards, can contribute to maintaining their productivity, protecting them from erosion, increasing the level of organic matter and increasing the stock of organic carbon. This study aimed to determine the organic carbon stored in the soil up to 20 cm depth in citrus orchards under different soil management systems. An experiment was carried out in a ‘Nadorcott’ mandarin orchard where measurements were performed both in the tree rows (between the trees in the ridges) and in the inter-rows (between ridges). Two treatments were tested: A) tree row without ground cover and inter-row covered with spontaneous herbaceous vegetation and B) tree row with almond shell mulching and inter-row with a permanent cover of sown herbaceous vegetation. Soil organic matter varied between 1.97 ± 0.14 % in the tree row without ground cover and 4.68 ± 0.03 % in the inter-row with spontaneous vegetation cover. Regarding the organic carbon stocked in the soil of the orchard, mean values of 25.04 ± 1.15 Mg C ha-1 were obtained in treatment A) and 31.24 ± 3.98 Mg C ha-1 in treatment B).
- Effects of a severe recovery pruning in the productivity and fruit quality of two late orange cultivarsPublication . Matias, Pedro; Duarte, Beatriz; Mendonça, Angélica; Oliveira, Silvino; Barrote, Isabel; Guerrero, Carlos; Duarte, AmilcarCurrently, citrus production plays a major role in worldwide agriculture, especially in the Mediterranean. However, the typical irregular branch development and the formation of large canopies and dense exterior foliage can be significant limitations to light entry and air circulation through the canopy. Consequently, dead branches appear in the inner canopy, which becomes unproductive; flowering and vegetative growth occur only on the outer canopy, and the fruits formed usually are of lower quality. Furthermore, dead branches can be an inoculum for some pathogenic microorganisms, chemical treatments become less efficient since reaching the inner canopy branches becomes more difficult, and fruit harvest becomes harder and more expensive. Pruning is a cultural practice that allows canopy management and the control of the problems mentioned above. However, many citrus growers avoid or postpone pruning, or prune insufficiently due to pruning’s high costs and, sometimes, direct production losses. To assess the effects of pruning, two experiments were performed on large canopy trees: one in ‘Valencia Late’ and the other in ‘Dom João’. In both experiments, some trees were left unpruned (control) and others were severely pruned in November 2019 (recovery pruning). The pruning was made by removing at least 30% of the canopy, with the complete removal of a few large branches. Pruning allowed a significant increase in light availability inside the canopy. In the 2020 harvest, there were no differences in fruit size between treatments. The production decreased in the pruned trees in the ‘Dom João’ experiment, as expected, and was similar in the ‘Valencia Late’ experiment. In the 2021 harvest, in both experiments, the pruned trees had a smaller canopy, and the production was similar in both treatments. However, the fruits from pruned trees were bigger in the ‘Dom João’ experiment and several quality parameters were better in the ‘Valencia Late’ experiment.