RESUMO: Em experimento de casa de vegetação, cultivou-se Brachiaria brizantha Stapf. cv. Marandu em solução nutritiva, tendo como tratamentos a solução completa, as omissões individuais de N, P, K, Ca, Mg, S e a testemunha (com omissão dos macronutrientes). Fez-se o acompanhamento da manifestação dos sintomas visuais de deficiência e, 50 dias após o transplante, avaliou-se a produção de matéria seca (MS), número de perfilhos (NP), a altura das plantas (H), bem como a composição mineral da parte aérea e das raízes. As omissões de N e P limitaram o crescimento, ao passo que a omissão de K não afetou a produção de MS e NP. A omissão de Ca não trouxe, para o período considerado, restrições na produção de MS, NP e H. Nas omissões de Mg e S as plantas tiveram fraco desempenho, superando apenas os tratamentos onde foram omitidos o N e o P. A composição mineral da parte aérea só apresentou diferenças acentuadas nos teores para os nutrientes omitidos. Sintomas visuais de deficiência foram observados para todas as omissões, sendo os primeiros manifestados através da omissão do N e do P e os últimos, através da omissão do Ca. São sugeridos estudos para melhor definição do balanço entre formas e fontes de nutrientes para a solução nutritiva quando utilizada no cultivo de plantas de Brachiaria brizantha cv. Marandu. Descritores: Brachiaria brizantha, nutrição mineral, macronutrientes, solução nutritiva, gramínea forrageira GROWTH OF Brachiaria brizantha Stapf. Cv. MARANDU IN NUTRIENT SOLUTION WITH MACRONUTRIENT OMISSIONSABSTRACT: In a greenhouse experiment Brachiaria brizantha Stapf, cv. Marandu was grown in a nutrient solution. The treatments were a complete nutrient solution, nutrient solutions with the omissions of each macronutrient (N, P, K, Ca, Mg and S) and a control (with the omission of all macronutrients). Plants were harvested 50 days after transplanting. Dry matter yield, tiller number and plant height were recorded, and nutrient concentrations in shoot and root were determined. Omissions of N and P were the most limiting for plant growth, whereas K and Ca did not affect grass growth and tillering. Mg and S omissions resulted in significant decreases in the plant parameters. Great decreases in plant nutrient concentrations were verified in the treatments with nutrient omissions in solution. Visual symptoms of deficiencies were observed for each nutrient omission treatment, with those of N and P being the first and that of Ca being the latest shown by the plants. Studies on forms and sources of nutrients for nutrient solution to be used with this grass are suggested. Key Words: Brachiaria brizantha, mineral nutrition, macronutrients, nutrient solution, forage grass INTRODUÇÃODiversas são as espécies de gramíneas forrageiras tropicais que apresentam-se como opções para a formação de pastagens no Brasil. As do gênero Brachiaria têm-se firmado pela capacidade de adaptação às diversas condições ambientais e de manejo da pastagem.A Brachiaria brizantha Stapf. cv. Marandu apareceu como mais uma opção para os pecuaristas...

Phosphorus (P) deficiency and aluminium (Al) phytotoxicity are major limitations for crop yield in acid soils. To ameliorate such limitations, agricultural management includes application of lime and P fertilisers, and the use of Al-tolerant plant genotypes. The mechanisms of Al tolerance and P efficiency may be closely related through strategies that decrease the toxicity of the Al3+ ion and increase P availability in soils. However, the effects of soils with high Al saturation on P acquisition by wheat have been little studied under field conditions. The aim of this work was to study Al–P interactions on wheat genotypes of contrasting Al tolerance when grown under field conditions in a volcanic soil with high Al saturation (32%) and low pH (5.0). A field-plot experiment was performed with winter wheat genotypes, two Al-tolerant (TCRB14 and TINB14) and one Al-sensitive (STKI14), with application of 0, 44 and 88 kg P ha–1. At the end of tillering and after physiological maturity (90 and 210 days after sowing), plants were harvested and yield and P and Al concentrations in shoots and roots were measured. Soil acid phosphatase, root arbuscular mycorrhizal (AM) colonisation, AM spore number and soil glomalin were determined. Shoot and root production and P uptake were higher in Al-tolerant genotypes than the sensitive genotype. In addition, root AM colonisation and soil acid phosphatase activity were also higher in tolerant genotypes. By contrast, Al concentration in shoots and roots was higher in the sensitive genotype with a concomitant decrease in P concentration. Grain yield of Al-tolerant genotypes was higher than of the Al-sensitive genotype with and without P fertiliser. Overall, the Al-tolerant genotypes were more effective at P acquisition from soil as well as from P fertiliser added, suggesting that plant traits such as Al tolerance, P efficiency, and AM colonisation potential co-operate in overcoming adverse acid soil conditions.