P. K. T. Jacomine

Funções de pedotransferência para predição da umidade retida a potenciais específicos em solos do estado de Pernambuco

Pedotransfer functions are equations used to estimate soil properties of difficult determination, based on other, more easily obtained soil properties. In spite of the considerable number of equations available to predict moisture retention to specific matrix potentials, these should not be used indiscriminatley,since most of them were developed in temperate climate soils, using data obtained by method that differ from the ones used in Brazilian laboratories. The objectives of this study were: (a) to develop pedotransference functions to estimate water retention at potentials between -33 and -1,500 kPa and water availability, using particle size distribution and global density data from soils of Pernambuco State, and (b) to compare the prediction efficiency of the new equations with similar equations available in literature. A database of 467 soil horizons from 98 soil profiles was used to develop the equations. The profiles were grouped, according to the Brazilian Soil Classification System, in 27 third category level classes (great group) The obtained equations showed worthwhile determination coefficients and low prediction standard error. Data grouping according to clay fraction, approximated development rate or textural class, did not improve the prediction capacity of the pedofunctions. The equations proposed in other works presented high prediction errors and are not recommended for soils of Pernambuco State.

Classificação de solos planossólicos do Sertão do Araripe (PE)

Soils with a planic B horizon underlying a textural B horizon and, therefore, not regarded as Planosols in the Brazilian System of Soil Classification (SIBCS) were characterized and classified. Three representative soil profiles were selected in the county of Ouricuri, Araripina micro-region, within the Sertao Zone of Pernambuco State, an area with a high density of planossolic soils. Soil profiles were morphologically described and disturbed samples taken from each horizon for physical and chemical analyses. Undisturbed samples were collected to determine bulk density. Results showed that the soils, formed by the contribution of two parent materials (sediments and crystalline rocks), demonstrate this double origin with two distinct sections. The top on is formed by A, BA, Bt, and/or Btf horizons, and the bottom one by 2Btbn and 2BCn horizons. The topsoil horizons have colors of higher chromas, lower clay contents, smaller bulk density, higher hydraulic conductivity, and a lower clay activity compared to the subsoil horizons, characterized by high bulk density, low chromas and very low hydraulic conductivity, limiting the downward movement of water. The soils were classified in the SIBCS as: Sodic Planossolic Eutric Argiluvic Plinthosol (profile 1); Solodic Planossolic Eutric Yellow Argisol (profile 2) and Sodic Planossolic Plinthic Eutric Yellow Argisol (profile 3). Changes in the definition of the planic B horizon were suggested to allow the inclusion of the studied soils as follows: a planic B horizon must not obligatorily underlie an A or E horizon nor present an abrupt particle size alteration as long as it presents abrupt transition that is a very clear rupture with the previous A, E or Bt horizon.

Structural quality of polyacrylamide-treated cohesive soils in the coastal tablelands of Pernambuco

Water-soluble polymers are characterized as effective flocculating agents due to their molecular features. Their application to soils with horizons with structural problems, e.g, a cohesive character, contributes to improvements in the physical quality and thus to the agricultural suitability of such soils. The purpose of this study was to evaluate the structural quality of soils with cohesive horizons of coastal tablelands in the State of Pernambuco treated with polyacrylamide (PAM) as chemical soil conditioner. To this end, three horizons (one cohesive and two non-cohesive) of a Yellow Argisol (Ultisol) were evaluated and to compare cohesive horizons, the horizon of a Yellow Latosol (Oxisol) was selected. The treatments consisted of aqueous PAM solutions (12.5; 50.0; 100.0 mg kg-1) and distilled water (control). The structural aspects of the horizons were evaluated by the stability (soil mass retained in five diameter classes), aggregate distribution per size class (mean weight diameter- MWD, geometric mean diameter - GMD) and the magnitude of the changes introduced by PAM by measuring the sensitivity index (Si). Aqueous PAM solutions increased aggregate stability in the largest evaluated diameter class of the cohesive and non-cohesive horizons, resulting in higher MWD and GMD, with highest efficiency of the 100 mg kg-1 solution. The cohesive horizon Bt1 in the Ultisol was most sensitive to the action of PAM, where highest Si values were found, but the structural quality of the BA horizon of the Oxisol was better in terms of stability and aggregate size distribution.

Pedogênese de planossolos em topossequência do agreste pernambucano

Os Planossolos assumem, na regiao do Agreste do Estado de Pernambuco, grande importância economica, tanto pela sua magnitude de ocupacao quanto pela utilizacao intensiva, especialmente com atividades agropecuarias. Aspectos como dualidade ou retrabalhamento do material de origem e natureza dos processos envolvidos na formacao das marcantes diferenciacoes texturais e nas concentracoes de Na e de sais sao pontos importantes a serem esclarecidos. Este trabalho teve como objetivo avaliar o processo de pedogenese dos Planossolos no Agreste de Pernambuco, com base nos resultados das analises fisicas, quimicas, mineralogicas, macromorfologicas e, especialmente, micromorfologicas. Foram estudados tres perfis de solos com marcante contraste textural, em trincheiras abertas ao longo de uma topossequencia de solos. Realizaram-se analises fisicas, quimicas, mineralogicas e macro e micromorfologicas. Verificou-se que os solos sao autoctones e que os nitidos contrastes texturais, devido a argilizacao dos horizontes Bt, parecem ser, principalmente, o resultado de uma combinacao de processos e nao uma simples eluviacao-iluviacao (lessivagem). Entre esses processos estao incluidos a intemperizacao de biotitas, com formacao in situ de argilas, e as perdas dessa fracao, devido a movimentacoes laterais por arraste mecânico ou dissolucoes. A combinacao exata desses processos, bem como a acumulacao de Na, foi fortemente influenciada pelo posicionamento dos solos no relevo.