Search Results (9)

Oil palms (Elaeis guineensis Jacq.) are increasingly cultivated throughout the humid tropics and are reported to have high transpiration rates. A potential contribution of stem water storage to transpiration has been discussed in previous studies. We assessed the water-use characteristics of oil palms at different horizontal and vertical positions in the plant by using three sap flux techniques, i.e., thermal dissipation probes, the heat ratio method and heat field deformation sensors. In a radial profile of the stem, sap flux densities were low at the outer margin, increased to 2.5 cm under the bark and remained relatively high to the innermost measured depth at 7.5 cm. In a vertical profile of the stem and with further sensors in leaf petioles, we found only small time lags in sap flux densities. Time lags along the flow path are often used for analyzing the contribution of water storage to transpiration. Thus, the small observed time differences in our study would leave only little room for the contribution of water storage to transpiration. However, water storage might still contribute to transpiration in ways that are not detected by time lag analysis. Such mechanisms may be explored in future studies. Full article

Currently, fertilization decisions in apple orchards are based on soil and leaf analyses while the leaf material is sampled after the growing season, usually in June–July (90–110 days after full bloom). This approach is inefficient, as the information becomes available later than the growing season and is therefore only useful in supporting fertilization decisions for the next year, not the current one. To establish a method that provides useful information for fertilization decisions earlier in the growth cycle, our research focused on the assessment of the nutrient content of petiole sap using different methods, the standard method and the rapid method using a reflectometer. For this study, in 2021, four ‘Gala’ orchards were fertilized with different N–P–K levels. Macro and micronutrients were determined in leaves and petiole sap at 45 and 90–110 days after full bloom (DAFB) using standard laboratory methods and the reflectometer. When leaf analysis at 45 and 90–110 DAFB was compared with petiole sap analysis at the same time point, no significant correlations were found between the nutrient contents in leaf material and petiole sap, with the exception of calcium. However, positive results were obtained regarding the correlation between reflectometer determination and standard laboratory analyses. The regression analysis revealed high determination coefficients for N-NO₃⁻ (R² = 0.703), K⁺ (R² = 0.705), Ca²⁺ (R² = 0.715), and Mg²⁺ (R² = 0.780) between standard laboratory methods and the reflectometer. These results suggest that the reflectometer enables a real-time diagnostic tool for monitoring nutrient status throughout the growth cycle, particularly key nutrients related to fruit quality. The N–P–K fertilization strategies had no influence on the nutrient content of leaves or petiole sap. The nutrient content of both sample types varied depending on the orchard. Full article

This work relates to greenhouse vegetable production in soil in Almeria, Spain. The prescriptive–corrective management (PCM) of irrigation and fertilization (N, P, K, Ca, and Mg) was evaluated. PCM combined recommendations (prescriptive management) for irrigation and nutrients made with the VegSyst-DSS v2, a decision support system, with monitoring (corrective management) using tensiometers (for irrigation) and petiole sap analysis (for nutrients). PCM was compared with conventional farmer management (CONV). The VegSyst-DSS v2 recommends applied nutrient concentrations considering simulated crop uptake, available soil nutrient supply, and evapotranspiration (ETc). This study was conducted with soil-grown tomato in a plastic greenhouse. Nutrients were applied in nutrient solution via drip fertigation. Compared to CONV management, PCM reduced irrigation by 25%, N, K, and Mg application by 40%, Ca by 58%, and P by 85%. There were no significant differences between treatments in fruit production and quality, despite appreciable reductions in irrigation and nutrient application. An economic analysis indicated that in this 7-month tomato crop, PCM compared to CONV management was associated with a financial saving of 1611 € ha⁻¹. These results showed that by using prescriptive–corrective fertigation management, based on the VegSyst-DSS v2, considerable savings can be achieved in water and nutrient (N, P, K, Ca, and Mg) inputs to greenhouse tomato without compromising production. This can reduce farmer costs and the environmental impact associated with these greenhouse production systems. Full article

Vermicompost has been promoted as a viable substrate component owing to its physicochemical properties, nutrient richness, and status as an excellent soil improver. It is considered the best organic fertilizer and is more eco-friendly than chemical fertilizers. Plant-growth-promoting microorganisms (PGPMs) are defined as plant biofertilizers that improve nutritional efficiency—that is, they transform nutrients within substrates from organic to inorganic forms, making them available for plants. The main objective of this research study is to evaluate the effects of the application of three PGPM microbial consortia on different mixtures of organic substrates based on vermicompost (V) and coconut fiber (CF) on two different horticultural crops. We performed a yield analysis and drainage nutrient tests and determined the plant nutritional status and enzymatic activity in organic substrates based on the two crops, Cucumis melo L. and Solanum lycopersicum L. A multivariate analysis of variance and principal component analysis was conducted using substrate types and PGPMs as factors. Differences (p < 0.05) in yield, dehydrogenase activity, the nutrient concentrations in a petiole sap, and drainage were observed at 30, 60, 75, and 90 days after transplant. PGPMs such as Trichoderma sp. and plant-growth-promoting rhizobacteria (PGPR) in organic substrates (40V + 60CF) can significantly improve the nutritional status of plants for use in organic soilless container agriculture. Biofertilization with PGPMs and suitable mixtures of organic substrates together with aqueous extracts (tea) of vermicompost, as nutrient solutions applied by fertigation, has allowed us to achieve an adequate level of production through environmentally friendly techniques. The results obtained allowed us to affirm that it was possible to replace conventional fertilization using no chemical products and ensure adequate crop nutrition by supplying main macronutrients with organic sources and biofertilizers. Full article

The inadequate management of agro-waste in intensive agriculture has a severe negative impact on the environment. The valorization of crop residue as a source of crop nutrients is a valid alternative to close the nutrient cycle and reduce the use of external input. In this study, plant material was incorporated into the soil as fresh crop residue, after either composting and vermicomposting processes, to evaluate their effects on tomato yield and nutritional status (petiole sap analysis: NO₃ and K⁺ concentration) over three crop cycles. A control treatment with mineral fertigation and an organic control treatment with goat manure were also included. Enzymatic activity and microbial population in the soil were evaluated. Although no differences between treatments were observed in the first cycle, in the second and third cycles, the yield obtained with the application of organic amendments derived from agro-waste was comparable to the yield obtained with mineral fertilizers. Overall, the sap analysis did not reveal a clear relationship with yield performances. The compost treatment resulted in higher microorganism presence in the soil. Soil dehydrogenase activity (DHA), acid phosphatase activity (ACP), and β-glucosidase activity (β-GLU) were generally more stimulated when organic amendments were used. The study confirms the applicability of soil fertilizers derived from agro-waste as a good alternative to mineral fertilizers. Full article

A rapid analysis ion-selective electrode (ISE) system for measurement of [NO₃⁻] in nutrient solution (NS), soil solution (SS) and petiole sap (PS) was evaluated. For each material, there were 797–2010 samples from 5 to 6 different crops, and from 2 to 4 different species. Accuracy was evaluated by linear regression (LR) with laboratory analysis (automated colorimetry, Cd reduction), and by relative error (RE), the average percentage deviation from laboratory analysis. For NS, the LR was y = 0.982x + 0.76, R² = 0.962 (n = 2010), for combined data from 5 crops (3 pepper, 2 cucumber). For SS, the LR was y = 0.975x + 1.13, R² = 0.965 (n = 797), for combined data from 5 crops (3 pepper, 2 cucumber). For undiluted PS, the LR relationship was y = 0.742x + 168.02, R² = 0.892 (n = 1425), for combined data from 6 crops (3 pepper, 2 cucumber, 1 melon). The underestimation was most pronounced at [NO₃⁻] of >1500 mg NO₃⁻–N L⁻¹. For diluted petiole sap (dilution by 10 for pepper and melon, 5 for other species), the LR relationship was y = 1.010x + 99.26, R² = 0.927 (n = 1182), for combined data from 6 crops (2 pepper, 2 cucumber, 1 melon, 1 tomato). RE values for all measurements in composite datasets were 14%, 22%, 24% and 25% for NS, SS, undiluted PS and diluted PS respectively, and they were lower in concentrations most likely to be measured in practical on-farm work. The ISE system measured [NO₃⁻] in NS, SS and diluted PS with sufficient accuracy to effectively guide on-farm decision making. Full article

Conductance of CO₂ across the mesophyll (G_m) frequently constrains photosynthesis (P_N) but cannot be measured directly. We examined G_m of cherry (Prunus avium L.) subjected to severe drought using the variable J method and carbon-isotopic composition (δ¹³C) of sugars from the centre of the leaf, the leaf petiole sap, and sap from the largest branch. Depending upon the location of the plant from which sugars are sampled, G_m may be estimated over scales ranging from a portion of the leaf to a canopy of leaves. Both the variable J and δ¹³C of sugars methods showed a reduction in G_m as soil water availability declined. The δ¹³C of sugars further from the source of their synthesis within the leaf did not correspond as closely to the diffusive and C-isotopic discrimination conditions reflected in the instantaneous measurement of gas exchange and chlorophyll-fluorescence utilised by the variable J approach. Post-photosynthetic fractionation processes and/or the release of sugars from stored carbohydrates (previously fixed under different environmental and C-isotopic discrimination conditions) may reduce the efficacy of the δ¹³C of sugars from leaf petiole and branch sap in estimating G_m in a short-term study. Consideration should be given to the spatial and temporal scales at which G_m is under observation in any experimental analysis. Full article

The aim of this work is to evaluate the relationship between the nutrient concentration in petiole sap and different agronomic and climatic variables for a tomato crop grown in a greenhouse in Mediterranean conditions. In addition, the persistence of the nutrient concentration in petiole sap was investigated with the aim of determining the sampling period that implies the best trade-off nutritional information. The experiment consisted of the selection of 20 sampling points inside the greenhouse. The samples of petiole, fully expanded leaf, and soil solution samples were collected weekly from 86 to 163 days after transplanting. Chloride, NO₃⁻-N, H₂PO₄⁻-P, Na⁺, K⁺, Ca²⁺, and Mg²⁺ concentrations were determined in petiole sap and soil solution obtained by suction cups. Nitrogen, P, K, Cl, and Na concentrations were also determined in leaf. Finally, the petiole sap nutritional diagnosis method is the highest sensitive nutritional diagnosis method which compares soil solution and nutrient leaf content related to yield, and the statistical analysis performed in this research demonstrates that crop evapotranspiration (ETc), vapor pressure deficit (DPV), and leaf area index (LAI) are considered the most significant variables that allow the development of these empirical prediction models regarding nutrient concentration in petiole sap. Full article

Nitrogen concentration in plants is normally determined by expensive and time consuming chemical analyses. As an alternative, chlorophyll meter readings and N-NO₃ concentration determination in petiole sap were proposed, but these assays are not always satisfactory. Spectral reflectance values of tomato leaves obtained by visible-near infrared spectrophotometry are reported to be a powerful tool for the diagnosis of plant nutritional status. The aim of the study was to evaluate the possibility and the accuracy of the estimation of tomato leaf nitrogen concentration performed through a rapid, portable and non-destructive system, in comparison with chemical standard analyses, chlorophyll meter readings and N-NO₃ concentration in petiole sap. Mean reflectance leaf values were compared to each reference chemical value by partial least squares chemometric multivariate methods. The correlation between predicted values from spectral reflectance analysis and the observed chemical values showed in the independent test highly significant correlation coefficient (r = 0.94). The utilization of the proposed system, increasing efficiency, allows better knowledge of nutritional status of tomato plants, with more detailed and sharp information and on wider areas. More detailed information both in space and time is an essential tool to increase and stabilize crop quality levels and to optimize the nutrient use efficiency. Full article