Montesquieu da Silva Vieira

Saline water and liquid bovine manure in seedlings formation of guava cultivar Paluma

The salinity of the soils and of the waters, in a lot of arid and semi-arid areas of the Brazilian northeast constitutes a serious obstacle for the system of agricultural production. During the period from November 2007 to February 2008 an experiment was carried out in order to evaluate the effects of the irrigation water salinity and liquid bovine manure during the seedlings formation of guava cv. Paluma. The treatments were distributed in a randomized block design, in a factorial scheme 5 x 2, referring to levels of water salinity (0.5, 1.0, 2.0, 3.0 and 4.0 dS m-1) in soil without and with liquid bovine manure in six replications and six plants per plot. Soil salinity was markedly elevated with an increasing salinity of irrigation water reflecting on decline of plant growth in height, stem diameter, leaf area, growth of roots and biomass production by guava plants, but with less intensity in plants with liquid bovine manure. The plants under irrigation with saline water and the organic product exceeded those treatments without the product at 86.9, 72.4, 11.0, 252.4, 351.0 and 39.7% of growth in height, stem diameter, length of roots, leaf area and biomass of roots and shoots respectively.

EFICIÊNCIA DE EXTRATORES DE POTÁSSIO DISPONÍVEL EM SOLOS DO ESTADO DA PARAÍBA COM GRAUS DE DESENVOLVIMENTO PEDOGENÉTICO DIFERENTES

Potassium availability for plants depends on the contents of the K forms present in the soils (non exchangeable, exchangeable and soluble K), which vary according to the degree of pedogenetic development of soils. The objective of this study was to evaluate K availability in soils with different degrees of pedogenetic development, based on the extraction of K from the soils with different extractants and with corn plants. Samples of the surface layer (0-30 cm) were collected from 12 representative soils in the state of Paraiba, of which six were more and six less developed. To the three replications of all 12 soils, five K doses (0; 50; 100; 200, and 300 mg dm-3) were applied in the form of KCl in solution and incubated for 21 days. Following, a sub-sample of 0.2 dm-3 of each soil was taken to determine the content of available K by the extractors Mehlich-1, Mehlich-3 and ion exchange resin. Then, corn was grown on the soils in a greenhouse for 30 days and the dry matter production and K plant content evaluated. The extractants Mehlich-1, Mehlich-3 and ion exchange resin extracted similar K amounts in the more developed soils. In the group of less developed soils, the extractants Mehlich-1 and Mehlich-3 extracted not very different K amounts, but much greater amounts than by ion exchange resin, especially in the soils with higher clay content and a larger proportion of 2:1 minerals. Unlike the extractants Mehlich-1 and Mehlich-3, ion exchange resin was not well-related with the exchangeable K content in the less developed soils. In this soil group, Mehlich-1 correlated best with the plant K content. In most soils the dry matter production of the plant did not increase with increasing K doses, but in all soils the K plant content increased in response to K fertilization.

Formas de potássio em solos representativos do Estado da Paraíba

Os solos do Estado da Paraiba apresentam grande diversidade de caracteristicas quimicas, fisicas e mineralogicas, acarretando em variacoes nos teores e formas de K disponiveis no solo. Objetivou-se com este trabalho avaliar os teores de K nao-trocavel, K trocavel e K soluvel em doze solos do Estado da Paraiba, na ausencia e na presenca de fertilizacao potassica, e correlaciona-los com as caracteristicas quimicas, fisicas e mineralogicas desses solos. O estudo constou de 60 tratamentos, sendo 12 solos e cinco doses de K (0; 50; 100; 200 e 300 mg dm-3) na forma de cloreto de potassio, com tres repeticoes. Apos receberem os tratamentos, os solos foram incubados por um periodo de 21 dias, e em seguida, uma sub-amostra de 0,2 dm3 de cada solo foi retirada para determinacao dos teores de K nao-trocavel, K trocavel e K soluvel. Os solos formados sob clima semiarido foram os solos que apresentaram as maiores reservas de K nao-trocavel. Solos com maior proporcao de mica e minerais do tipo 2:1 na fracao argila apresentaram os maiores teores de K nao-trocavel e K trocavel. Independente do grupo de solos, os teores de silte apresentaram correlacao elevada com os teores de K nao-trocavel e de K trocavel. Nos solos mais desenvolvidos, nao foi evidenciada fixacao de K proveniente do fertilizante. Porem, nos solos menos desenvolvidos, a fixacao de K ficou evidenciada pela pequena quantidade de K recuperada pelo extrator acetato de amonio nos solos mais argilosos e, principalmente, naqueles com predominância de minerais do tipo 2:1 e mica.