Percorrer por autor "Jongen, Marjan"
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- Assessing the Role of Phosphorus, Starter Nitrogen and Boron in Subterranean Clover and Annual Ryegrass Grown in Acidic Soils Under Mediterranean Conditions in PortugalPublication . Sawimbo, Almeida; Aguiar, Peltier; Arrobas, Margarida; Aguiar, Carlos; Rodrigues, Nuno; Jongen, Marjan; Teixeira, Ricardo F. M.; Domingos, Tiago; Rodrigues, Manuel ÂngeloIn Mediterranean pasture systems, maintaining legume persistence and productivity is often constrained by phosphorus (P) deficiency in acidic soils. Although small doses of starter nitrogen (N) are commonly used in pulse crops to support early growth before N fixation begins, this practice has not been widely tested in legume-grass mixtures. In addition, boron (B), a micronutrient particularly important for dicot species, may also influence legume performance under these conditions. Thus, this study investigated the effects of P application on dry matter yield (DMY) and nutrient uptake in subterranean clover (Trifolium subterraneum L., cv. Denmark), annual ryegrass (Lolium multiflorum Lam., cv. Falladino) and their mixture, using a pot experiment with acidic soils from two distinct locations in Portugal. The study also evaluated the impact of a small N starter dose and B application. Although Soil 2 had higher acidity (pH 5.0) than Soil 1 (pH 5.4), it supported greater biomass production, likely due to its higher organic carbon (C) content (50.8 g kg-1), which may have buffered soil acidity. P application significantly increased P uptake, DMY and N accumulation in legumes, suggesting a critical role in nodulation and/or nodule function. The N starter had no significant effect, likely because sufficient N was released from soil organic matter prior to the onset of biological N fixation. While the B application increased tissue B concentrations, it did not affect DMY, possibly because B was adequately available from organic matter. These findings highlight the importance of P in legume management in pasture systems and suggest that, in soils with sufficient organic matter, the application of starter N and B may not be necessary.
- Evaluating soil phosphorus tests and nutrient limitations in Mediterranean pasturesPublication . Arrobas, Margarida; Raimundo, Soraia; Sawimbo, Almeida; Rodrigues, Nuno; Jongen, Marjan; Teixeira, Ricardo F.M.; Domingos, Tiago; Rodrigues, Manuel ÂngeloReliable phosphorus (P) fertilization guidelines for Mediterranean pastures remain uncertain due to inconsistent soil testing methods, the complexity of mixed-species systems, and the neglect of other limiting nutrients. This study primarily aimed to identify reliable soil P tests and secondarily to explore potential nutrient limitations by assessing seven acidic Portuguese soils under Mediterranean conditions using subterranean clover (Trifolium subterraneum) and ryegrass (Lolium multiflorum) as model species. Five P extraction methods (Egner-Riehm, Olsen, Bray II, Mehlich I, and anion exchange resin) were compared alongside a pot experiment with clover, ryegrass, and their mixture. Biomass production, plant nutritional status, and soil-plant relationships were used to assess nutrient availability and plant response. The Egner-Riehm method proved the most reliable, showing linear correlation with the resin method (R2 = 0.89), widely regarded as the best indicator of soil P bioavailability. P availability was therefore not a limiting factor for biomass production. The lowest soil P content (54 mg kg-1 P2O5, Egner-Riehm) was close to the medium threshold (50-100 mg kg-1), yet plant growth indicated adequacy. In contrast, nitrogen (N) emerged as the main growth constraint, and boron (B) deficiency further restricted clover performance, confirming additional nutritional imbalances. A linear relationship between soil and tissue B supported its association with DMY, and tissue B levels were below sufficiency thresholds. Overall, in acidic Portuguese soils under Mediterranean conditions, soil P was adequate, whereas N and B acted as key constraints to productivity. These findings support more accurate and efficient fertilization strategies for Mediterranean pastures.
- Liming alone is not enough: The role of phosphorus and boron in supporting legume pasture growthPublication . Aguiar, Peltier; Arrobas, Margarida; Aguiar, Carlos; Rodrigues, Nuno; Jongen, Marjan; Teixeira, R.F.M.; Domingos; Tiago; Rodrigues, Manuel ÂngeloSoil fertility management is a critical factor for ensuring the persistence of the legume component in improved pastures in Mediterranean regions. To promote legume growth, the most common practices include the application of lime to correct Soil acidity and phosphate fertilizers to address phosphorus (P) deficiencies. This study examined two acidic soils and evaluated the need for P and boron (B) supplementation following liming. A factorial pot experiment (Soil type × vegetation type × fertilizer treatment) was conducted using subterranean clover (Trifolium subterraneum L.), annual ryegrass (Lolium multiflorum Lam.), and their mixture. Results revealed significantly higher dry matter yield (DMY) for the legume (18.1 g pot⁻¹) compared to the grass (5.9 g pot⁻¹), due to the legume's ability to access atmospheric nitrogen (N). Soil 2, which had higher initial P availability than Soil 1, and P fertilization both enhanced N accumulation in legume tissues, the percentage of N derived from the atmosphere (%Ndfa), and DMY. These outcomes indicate that liming alone was insufficient to increase P availability and eliminate the need for P fertilization. For instance, DMY increased from 15.0 g pot⁻¹ with liming alone to 19.4 g pot⁻¹ when P was supplemented. Additionally, B application increased N uptake and %Ndfa in the legume, with the latter rising from 48.9% in the liming-only control to 77.5% with B supplementation. These results suggest that liming, by increasing Soil pH, may reduce B bioavailability, highlighting the need for B supplementation following lime application.