Liming alone is not enough: The role of phosphorus and boron in supporting legume pasture growth
¹Instituto Superior Politécnico do Cuanza Sul (ISPCS), Rua 12 de Novembro, Sumbe P.O. Box 82, Angola
²Centro de Investigação de Montanha (CIMO), Instituto Politécnico de Bragança, Campus de Santa Apolónia, 5300-253 Bragança, Portugal
³Laboratório para a Sustentabilidade e Tecnologia em Regiões de Montanha, Instituto Politécnico de Bragança, Campus de Santa Apolónia, 5300-253 Bragança, Portugal
⁴Terraprima – Serviços Ambientais, Centro de Negócios do Porto Alto, Fracção S, Avenida das Nações Unidas, nº 97, 2135-199 Samora Correia, Portugal
⁵MARETEC − Marine, Environment and Technology Centre, LARSyS, Instituto Superior Técnico, Universidade de Lisboa, Av. Rovisco Pais, 1, 1049-001 Lisbon, Portugal
*Correspondence: angelor@ipb.pt
Abstract:
Soil 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.
Key words:
%Ndfa, annual ryegrass, biological nitrogen fixation, dry matter yield, Mediterranean pastures, subterranean clover