-• Chestnut stands (Castanea sativa Mill.) for fruit production, in Northern Portugal, are subjected to frequent soil tillage operations, which is considered a threat for the system sustainability.• The effects of replacement of conventional tillage by the no-tillage system in chestnut stands on decomposition and nutrient dynamics of leaf litter and burs were evaluated, using the litterbag methodology. Amounts of mass and nutrients in the organic layers, and chemical characteristics of the 0-20 cm top soil layer were assessed after eight years.• The mass loss and release of N, P, Ca and Mg from both leaves and burs buried in the soil were faster than from those placed on the soil surface. Burs decomposed and released nutrients more slowly than leaf litter. The no-tillage system led to the formation of organic layers, which retained great amounts of N (249.2 kg ha −1 ) and Ca (215.5 kg ha −1 ). Such a management system increased the concentration of organic C and nutrients in the 0-5 cm top soil layer, but significant differences were only observed for exchangeable Ca.• The no-tillage system may enhance organic C accumulation regarding the conventional system, due to the increment in both organic and mineral soil layers.litterfall decomposition / litterbag / nutrient dynamics / chestnut stand / soil management / decomposition models / no-tillage / conventional tillage Résumé -Décomposition des chutes de litière de châtaignier et huit années de changements chimiques du sol sous un système de gestion sans labour dans le Nord du Portugal.• Les peuplements de châtaignier (Castanea sativa Mill.) pour la production de fruits dans le Nord du Portugal font l'objet de fréquentes opérations de labour, qui sont considérées comme une menace pour un système de gestion durable.• Les effets de remplacement du labour traditionnel par un système sans labour dans les peuplements de châtaignier sur la décomposition et la dynamique des nutriments des feuilles de la litière et des bogues, ont été évalués en utilisant la technique des sacs à litière. La masse totale des nutriments dans les strates organiques et les caractéristiques chimiques de la partie supérieure (0-20 cm) du sol ont été estimées au bout de huit ans.• La perte de masse et la libération de N, P, Ca et Mg provenant des feuilles et des bogues enfouies dans le sol ont été plus rapides que dans le cas de feuilles et bogues placées à la surface du sol. Les bogues se décomposent et libèrent des nutriments plus lentement que les feuilles de la litière. Le système d'absence de labour a conduit à la formation de strates organiques, qui retiennent une grande quantité de N (249,2Kg ha −1 ) et de Ca (215,5 kg ha −1 ). Un tel système de gestion a accru la concentration en C organique et en nutriments dans la strate de la partie supérieure du sol (0-5cm), mais des différences significatives ont été observées seulement pour le Ca échangeable.• Le système sans labour peut accroître l'accumulation de C organique par rapport au système traditionnel à cause de l'accroissement ...
Chestnut plantations for fruit production in Northern Portugal have been subjected to intensive management system, including soil tillage, mineral fertilization and pruning. Some of these practices have no positive effect on productivity and soilplant-water relations. Other systems (e.g., no tillage with maintenance of grass cover) have been adopted, aiming a multifunctional land use, exploiting nuts, pasture and edible mushrooms. Thus, an experimental trial was installed to assess the effects of such systems on productivity, sustainability and annual net income, as compared with the conventional system, over a six-year period. The treatments were: conventional soil tillage (CT); no tillage with permanent spontaneous herbaceous vegetation cover (NV); no tillage with permanent rainfed seeded pasture cover (NP); and as NP but with irrigation (NIP). Production of nuts, forage and edible mushrooms were measured and sustainability was assessed by production and diversity of fungal sporocarps. Annual net income was estimated by the difference between the annual gross outputs (market values for nuts, forage and edible commercial mushrooms) and the annual input costs. The greatest nut and edible mushroom production and sporocarp biodiversity were achieved in the NIP and NV and the smallest in the CT treatment. The highest annual gross output was estimated for the NV and NIP treatments, whereas the highest annual net income was obtained for the NV. No tillage with maintenance of spontaneous grass cover showed to be the most favourable management system, as it has increased productivity and biodiversity.
The effects of different soil management practices and irrigation on plant water relations, physiological response and productivity of chestnut stands in Northeastern Portugal were assessed during four growing seasons (2003 to 2006). Treatments were: conventional soil tillage up to 15-20 cm depth with a tine cultivator thrice a year (CT); no tillage with spontaneous herbaceous vegetation (NV); no tillage with rainfed seeded pasture (NP); and no tillage with irrigated seeded pasture (NIP). Results suggest that soil water availability was the most critical parameter for chestnut productivity over the study period. In all treatments, high predawn leaf water potentials (-0.40 to -0.55 MPa) were observed during the dry seasons of 2003, 2004 and 2006, showing no critical conditions for plant productivity, which is ascribed to water availability in deep soil layers. In contrast, in 2005, an extremely dry year, water potentials decreased and varied from -1.46 to -1.72 MPa in late summer, showing unfavourable conditions for nut production. Maintenance of spontaneous herbaceous vegetation without irrigation enhanced productivity of chestnut stands as compared with the conventional tillage system and the no tillage system with seeded pasture. Productivity in the soil watering system (NIP treatment) was not significantly different from that observed in the NV treatment. Therefore, studies on the irrigation strategy should be developed, in order to increase its efficiency especially in stands with young trees.
Fusarium oxysporum exhibits insect pathogenicity—however, generalized concerns of releasing phytopathogens within agroecosystems marred its entomopathogenicity-related investigations. In a previous study, soils were sampled from Douro vineyards and adjacent hedgerows. In this study, 80 of those soils were analyzed for their chemical properties and were subsequently co-related with the abundance of entomopathogenic F. oxysporum, after insect baiting of soils with Galleria mellonella and Tenebrio molitor larvae. The soil chemical properties studied were organic matter content; total organic carbon; total nitrogen; available potassium; available phosphorus; exchangeable cations, such as K+, Na+, Ca2+, and Mg2+; pH; total acidity; degree of base saturation; and effective cation exchange capacity. Entomopathogenic F. oxysporum was found in 48 soils, i.e., 60% ± 5.47%, of the total soil samples. Out of the 1280 insect larvae used, 93, i.e., 7.26% ± 0.72%, were found dead by entomopathogenic F. oxysporum. Stepwise deletion of non-significant variables using a generalized linear model was followed by a generalized linear mixed model (GLMM). A higher C:N (logarithmized) (p < 0.001) and lower exchangeable K+ (logarithmized) (p = 0.008) were found significant for higher fungal abundance. Overall, this study suggests that entomopathogenic F. oxysporum is robust with regard to agricultural changes, and GLMM is a useful statistical tool for count data in ecology.
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