Frutos de goiaba (Psidium guayava L.): desenvolvimento e extração de nutrientes

An orchard of guava (Psidium guayava L.) located in Aliança, SP, Brazil, had its fruits picked up at 15 to 90 days of age, in 15-day intervals. The soil was an Ultisol and the three varieties studied were: Okawa n° 2, Pedro Sato and Kumagai. The fruits were dried, weighed, grounded and analysed for all the macronutrients and for the micronutrients B, Cu, Fe, Mn and Zn. The highest fruit weights were obtained at 60 days of age for the Pedro Sato and Kumagai varieties, whereas the same happened at 75 days for the Okawa n° 2 variety. Fruits harvested from Pedro Sato and Kumagai plants removed more nutrients than those from Okawa n° 2 plants. The three varieties removed macronutrients in the following increasing order: Mg, Ca, P, S, N and K. Among the micronutrients, B, Zn and Fe had the highest amounts removed by fruits, whereas Cu had the lowest.Em um pomar de goiabeira implantado em um solo Podzolizado de Lins e Marília variação Lins, situado no Município de Aliança, SP, foram coletados frutos desde os 15 dias até os 90 dias de idade, com intervalos de 15 dias, nas variedades de mesa Okawa n° 2, Pedro Sato e Kumagai. O frutos foram secados, pesados e analisados para todos os macronutrientes e para os micronutrientes B, Cu, Fe, Mn e Zn. As variedades Pedro Sato e Kumagai tiveram peso máximo dos frutos aos 60 dias e exportaram maiores quantidades dos nutrientes que a variedade Okawa n° 2, que teve peso máximo dos frutos aos 75 dias. Nas três variedades a exportação dos macronutrientes por planta e por unidade de área obedeceu a seguinte ordem crescente: Mg, Ca, P, S, N e K. Entre os micronutrientes o B, o Zn e o Fe foram os mais exportados, o Mn foi intermediário e o Cu foi o de menor exportação

Magnetotelluric Imaging of the Lithosphere Across the Variscan Orogen (Iberian Autochthonous Domain, NW Iberia)

A new magnetotelluric (MT) survey comprising 17 MT soundings throughout a 30 km long N30°W transect in the Iberian autochthons domain of NW Iberia (Central Iberian Zone) is presented. The 2-D inversion model shows the resistivity structure of the continental crust up to 10 km depth, heretofore unavailable for this region of the Variscan Orogen. The MT model reveals a wavy structure separating a conductive upper layer underlain by a resistive layer, thus picturing the two main tectonic blocks of a large-scale D2 extensional shear zone (i.e., Pinhel shear zone). The upper layer represents a lower grade metamorphic domain that includes graphite-rich rocks. The lower layer consists of high-grade metamorphic rocks that experienced partial melting and are associated with granites (more resistive) emplaced during crustal thinning. The wavy structure is the result of superimposed crustal shortening responsible for the development of large-scale D3 folds (e.g., Marofa synform), later deflected and refolded by a D4 strike-slip shear zone (i.e., Juzbado-Penalva do Castelo shear zone). The later contribution to the final structure of the crust is marked by the intrusion of postkinematic granitic rocks and the propagation of steeply dipping brittle fault zones. Our study demonstrates that MT imaging is a powerful tool to understand complex crustal structures of ancient orogens in order to design future prospecting surveys for mineral deposits of economic interest

Cultivo de Brachiaria brizantha Stapf. cv. Marandu em solução nutritiva com omissões de macronutrientes

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.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

Decomposition and nutrient release of leguminous plants in coffee agroforestry systems.

Leguminous plants used as green manure are an important nutrient source for coffee plantations, especially for soils with low nutrient levels. Field experiments were conducted in the Zona da Mata of Minas Gerais State, Brazil to evaluate the decomposition and nutrient release rates of four leguminous species used as green manures (Arachis pintoi, Calopogonium mucunoides, Stizolobium aterrimum and Stylosanthes guianensis) in a coffee agroforestry system under two different climate conditions. The initial N contents in plant residues varied from 25.7 to 37.0 g kg-1 and P from 2.4 to 3.0 g kg-1. The lignin/N, lignin/polyphenol and(lignin+polyphenol)/N ratios were low in all residues studied. Mass loss rates were highest in the first 15 days, when 25 % of the residues were decomposed. From 15 to 30 days, the decomposition rate decreased on both farms. On the farm in Pedra Dourada (PD), the decomposition constant k increased in the order C. mucunoides < S. aterrimum < S. guianensis < A. pintoi. On the farm in Araponga (ARA), there was no difference in the decomposition rate among leguminous plants. The N release rates varied from 0.0036 to 0.0096 d-1. Around 32 % of the total N content in the plant material was released in the first 15 days. In ARA, the N concentration in the S. aterrimum residues was always significantly higher than in the other residues. At the end of 360 days, the N released was 78 % in ARA and 89 % in PD of the initial content. Phosphorus was the most rapidly released nutrient (k values from 0.0165 to 0.0394 d-1). Residue decomposition and nutrient release did not correlate with initial residue chemistry and biochemistry, but differences in climatic conditions between the two study sites modified the decomposition rate constants