Renato Lemos dos Santos

Produção de capim elefante e movimentação de cátions em função de gesso mineral

The use of gypsum in context of exchangeable acidity in subsurface has provided the improvement of root environment, positive influence on crop yields. Therefore, the aim of this study was to evaluate the potential of the mined gypsum from the Araripe region in increasing the exchangeable Ca and also the reduction of exchangeable Al in subsurface, and increase in biomass production of varieties of elephant grass. The experiment was composed of three varieties of elephant grass, such as, Cameroon, Gramafante and Roxo in the presence and absence of mined gypsum through a factorial arrangement (3 x 2), with treatments arranged in 4 randomized blocks. The levels of Ca2+, S-SO42-, Al3+ and also its saturation were not affected by the application of mined gypsum in the soil subsurface layer. The application of mined gypsum reduced the pH of the soil subsurface layer. The growing of Cameroon variety promoted the increase in soil pH, reducing the Al saturation. The Cameroon and Gramafante had high dry matter yields, but only the Cameroon variety presented response to application of gypsum, which reached 33 Mg ha-1.

Extração e eficiência de uso de nutrientes em capim-elefante na presença de gesso

O cultivo de capim-elefante (Pennisetum purpureum Schum) na regiao do Polo Gesseiro do Araripe, localizada a oeste do Estado de Pernambuco, no Nordeste do Brasil, pode ser uma alternativa viavel de energia, em especial quando se realiza a correcao da fertilidade do solo. O objetivo deste trabalho foi avaliar o efeito do gesso no estado nutricional, na composicao mineral, na producao de biomassa e na extracao e eficiencia de nutrientes de variedades de capim-elefante na Chapada do Araripe, Estado de Pernambuco. Para isso, foram cultivadas tres variedades de capim-elefante - Cameroon, Gramafante e Roxo - na presenca e ausencia de gesso em blocos casualizados em arranjo fatorial (3 x 2), com quatro repeticoes. Os capins-elefante Cameroon e Gramafante apresentaram elevadas producoes de materia seca, porem apenas a variedade Cameroon mostrou resposta a aplicacao de gesso, tendo alcancado 33 Mg ha-1. O capim-elefante Gramafante foi mais eficiente no uso de Ca que as variedades Cameroon e Roxo.

Sampling of Sugarcane Leaves in Field Experiments to Determine the Activity of Nitrate Reductase

ABSTRACT Nitrogen (N) assimilation depends on nitrate reductase activity (NRA). Leaf sampling methods in field experimentation with sugarcane and analytical procedures are essential for the determination of the maximum activity (MA) of the enzyme. Thus, in five tests, it was possible to determine which period of the crop cycle should be used for leaf collection, the most adequate leaf for collection, the ideal number of leaves to be collected, the period of the day in which the enzyme has MA and which analytical procedures can be optimized. The evaluation of NRA in sugarcane should occur between 95 and 100 days after planting (DAP) and can be performed in any green leaf. In field experiments, it is recommended the collection of 15 leaves, which must occur between 12:00 and 12:30 h, with later incubation of the leaf tissues for 430 min, without vacuum application.

SOLOS FLORESTAIS EM FRAGMENTO DE FLORESTA URBANA NA MATA DE DOIS IRMÃOS, RECIFE, PERNAMBUCO, BRASIL

The forest remnant that composes ‘Parque Estadual Dois Irmaos’ (PEDI) is regarded as one of the largest urban forest fragments in Brazil. There are reports of frequent occurrence of healthy fall trees in the park, in natural conditions, which may compromise its natural balance and its function as an urban forest fragment. Probably, this phenomenon is associated to the chemical and physical properties of the soils comprising PEDI. So, this research aimed to evaluate PEDI soils chemical and physically, identifying, mapping and analyzing the soils in the occurrence of falling tree areas at the research locus. Twelve points of sampling in a representative area of PEDI were mapped, where deformed samples were collected at depths 0-0.10; 0.10-0.30 and 0.30-0.60 m, and not deformed samples at depths 0-0.05 and 0.10-0.15 m. The chemical attributes and part of the physical attributes were determined in the deformed samples. And other physical attributes were determined in the undisturbed samples. The soils of PEDI were low in natural fertility. They have acid reaction and high concentrations of Al 3+ to 0.60 m, and this can create chemical barriers that damage the growth of the plant roots and may be the cause of the frequent tree falling in the park. The soils were classified as clayed to very clayed, very permeable to vertical and lateral water movement. They had high variability in hydraulic conductivity and sharp decrease of water volumetric content in applying small stresses in surface layers as well as higher water retention by soil in Oxisol subsurface. In order to extend the information and create a database for future studies, it is suggested the monitoring of the most vulnerable species to fall, and analyzing other chemical and physical properties of PEDI soils, also opening profiles to understand tap root dynamics.