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Weeds reduce crop yields and require annual measures of control, although they can provide important ecological benefits. In this work, the efficacy was tested of an ecological fertilizer with herbicidal properties (Bioscrop Herbitec®) which in high concentrations (10-15%) can have a similar effect to a contact herbicide. The composition of the product is 6.0 % of water-soluble potassium oxide, 54.7 % of organic acids and 39.3 % of dispersants and diluents. The product was tested in six field trials during two years, which included two vineyards and two olive orchards and winter and spring vegetation. In each experiment three treatments were imposed, being the product applied at the concentrations of 10% and 15% and a non-treated control. In treated plots, the entire ground surface (rows and inter-rows) was sprayed. The evaluation of the effect of the treatments on vegetation was assessed by the pin point and grid methods which consisted of determining the percentage of damaged and not damaged vegetation and bare soil. The production of dry biomass of weeds was also evaluated as a measure of the persistence of the damage on vegetation. The floristic composition of the stands was also recorded to evaluate the specific susceptibility of the weeds to the different treatments. The results showed that the product severely damaged the vegetation, and the effect persisted for more than a month. The application of the product caused a severe reduction in the aboveground biomass while keeping the soil protected, showing a useful compromise between the reduction in weed competition and the maintenance of ground cover. Some species were severely damaged while others seemed to have benefited in relative terms, suggesting that the effectiveness of the product will be dependent on the weed species present.

The application of fertilizers as a topdressing in maize raises serious concerns because too much fertilizer is retained in the upper leaves, causing burning to the tissues. In this study, the use of a controlled-release and a stabilized fertilizer (with 3, 4-dimethylpyrazole phosphate) was compared with the application of a conventional fertilizer split into two equivalent applications in a forage maize-oats cropping system. In maize, 100 and 200 kg N ha−1 of different fertilizers were used in addition to an unfertilized control. The oat crop was not fertilized, since it served only as a winter catch crop. Maize dry matter (DM) yield increased significantly with N rate only in 2019, being the second growing season, with the control showing the lowest average value (7.1 t ha−1). The most fertilized treatments (200 kg N ha−1) gave the highest DM yields, ranging between 14.2 and 16.7 t ha−1, but with no significant differences between them. Oats had a relevant role as a catch crop recovering residual N that could have potentially been lost from the soil. Stalk nitrate concentration proved to be very sensitive to N fertilization (varying from 150.4 to 1945.6 mg kg−1 in 2018 and 494.9 to 1574.9 mg kg−1 in 2019), showing great potential as a tool of N management. These three fertilization strategies seem to be valid options that farmers can consider, after incorporating technical-economic information related to equipment suitability and the price of fertilizers. [ABSTRACT FROM AUTHOR]

BACKGROUND: Cropping practices focusing on agronomic water use efficiency and their impact on quality parameters must be investigated to overcome constraints affecting olive groves. We evaluated the response of olive trees (Olea europaea, cv. 'Cobrançosa') to different water regimes: full irrigation (FI, 100% crop evapotranspiration (ETc)), and three deficit irrigation strategies (DIS) (regulated (RDI, irrigated with 80% of crop evapotranspiration (ETc) in phases I and III of fruit growth and 10% of ETc in the pit hardening stage), and two continuous sustained strategies (SDI) – a conventional SDI (27.5% of ETc), and low‐frequency irrigation adopted by the farmer (SDIAF, 21.2% of ETc). RESULTS: The effects of water regimes on the plant water status, photosynthetic performance, metabolite fluctuations and fruit quality parameters were evaluated. All DIS treatments enhanced leaf tissue density; RDI and SDI generally did not affect leaf water status and maintained photosynthetic machinery working properly, and the SDIAF treatment impaired olive tree physiological indicators. The DIS treatments maintained the levels of primary metabolites in leaves, but SDIAF plants showed signs of oxidative stress. Moreover, DIS treatments led to changes in the secondary metabolism, both in leaves and in fruits, with increased total phenolic compounds, ortho‐diphenols, and flavonoid concentration, and higher total antioxidant capacity, as well higher oil content. Phenolic profiles showed the relevance of an early harvest in order to obtain higher oleuropein levels with associated higher health benefits. CONCLUSION: Adequate DIS are essential for sustainable olive growing, as they enhance the competitiveness of the sector in terms of olive production and associated quality parameters. © 2019 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

The SPAD-502 and the FieldScout CM 1000 chlorophyll meters were compared in their performance in diagnosing the nutritional status of plants. Leaves of a wide range of greenness were used to push the sensitivity of the tools to their limits. Both devices showed high reproducibility when used by different operators. The SPAD-readings were well-correlated with leaf nitrogen (N) concentrations, since leaves from heavily fertilized plants were not included in the sample population. The FieldScout-readings showed a marked saturation curve with the leaf N concentration, thus it cannot be used as a reliable N nutritional status index. The results also showed that the use of SPAD-502 in the diagnosis of the nutritional status of an orchard requires the establishment of specific critical concentrations for cultivars and sampling dates. The SPAD-502 appeared to have potential in the diagnosis of the nutritional status of the orchard for nutrients other than N. [ABSTRACT FROM AUTHOR]

European chestnut is the most important cash crop in the highlands of NE Portugal. However, limited data on cropping technique are available to help farmers make decisions. This work is motivated by the lack of data related to chestnut response to fertilizer application. It reports results from a field fertilization trial consisting of the application of a combination of lime (L), nitrogen (N), phosphorus (P), potassium (K), and boron (B), namely LNPKB, NPKB, -NPKB, N-PKB, NP-KB, and NPK-B. Seedlings of chestnut were planted in June 2013 and grown for four growing seasons. Plant height, trunk diameter, and pruning wood were assessed every year and used as indicators of tree crop growth. Elemental leaf analysis and other tools [SPAD-502 chlorophyll meter; Field Scout CM 1000 NDVI (normalized difference vegetation index) meter, and the OS-30p+ fluorometer] were used to assess plant nutritional stresses. In January 2017 soil samples were collected at three depths (0-5, 5-10, and 10-20 cm) to determine several soil fertility parameters. The nonapplication of K and B reduced the tree crop growth and pruning residues. Leaf analysis revealed leaf K and B concentrations respectively in the NP-KB and NPK-B treatments to be in the deficient range previously established for chestnut. SPAD readings and NDVI detected the reduced availability of N associated with the -NPKB treatment but not the reduced plant growth associated with NP-KB or NPK-B treatments. The dark adaptation protocols of FV/FM, FV/F0, and OJIP measurements performed with the OS-30p+ fluorometer failed to diagnose the nutrient stresses detected by leaf analysis or the reduction in plant growth. [ABSTRACT FROM AUTHOR]

The adaptation of stevia to the growing conditions of NE Portugal is assessed, including the tolerance of this species to cold temperatures, and the potential to produce biomass when grown as an annual crop and when subjected to various nitrogen (N) rates and two harvesting regimes. Almost all the plants died during the winter of 2014 (minimum temperatures peaked at −8.0°C), making it necessary to replant the crop the following spring. With the best cutting regime (double cut) and N rate (150 kg N ha−1), 1514.4 and 2390.0 kg ha−1of dry leaves were produced, respectively, in 2014 and 2015. Leaf chlorophyll concentrations estimated by the SPAD (Soil and Plant Analysis Development)-502 chlorophyll meter and a NDVI (Normalized Difference Vegetation Index) carried out by the Field Scout CM 1000 spectroradiometer showed significant differences among N rates, proving to be good indicators of plant N nutritional status. Based on the leaf analysis, provisional sufficiency ranges for N are proposed, namely 25–35 g kg−1for mid-summer and 15–25 g kg−1for early autumn. The fluorescence of chlorophyllaand the transient fluorescence intensity performed by the OS-30p+ fluorometer failed to show any stress induced by no-N control treatments in comparison to N-treated plants. [ABSTRACT FROM PUBLISHER]

Urban agriculture is increasing in both developing and developed countries. In spite of its multiple benefits, urban agriculture can cause unwanted aspects such as environmental damage and health risks to consumers. This work was carried out in a social garden project developed by the Polytechnic Institute of Bragança, Portugal. It checked if cropping practices were environmentally sound and monitored the quality of the edible vegetables, in particular their concentration of trace metals. Bragança is a small city of 25,000 inhabitants located in Northeastern Portugal. In this study the plant nutritional status and the inorganic nitrogen (N) levels in the soil as indirect indicators of the risk of N loss to the environment; and the concentrations of trace metals in the soil and plant tissues as a measure of the exposure of gardeners to trace metals were studied. The results showed the existence of low leaf N concentrations, often close to the deficiency range of the respective species, and also low inorganic N levels in the soil during the winter, suggesting reduced risks of nitrate leaching and denitrification. Trace metal concentrations were low in the soils when compared with the limits set by national and international legislation. As a result, the content of trace metals in edible plant parts was also low. The positive results found in this urban agriculture project might be due to its organic farming basis and to the absence of major sources of pollution in the vicinity of the gardens. This information is useful to local gardeners, since they can trust the products they take home, but also to other urban agriculture projects in even more populated cities. [ABSTRACT FROM PUBLISHER]