Maria de F. C. Barros

Correção de solos salino-sódicos pela aplicação de gesso mineral

With the objective of quantifying the parameters that determine the effectiveness of gypsum in the reclamation of saline-sodic soils in the Irrigated Perimeter of Custodia located in the State of Pernambuco, Brazil, with the purpose of increasing the available areas for irrigated agriculture, an experiment was carried out in soil columns installed at the Soil Mechanics and Residue Recovery Laboratory at the Universidade Federal Rural de Pernambuco. The treatments were arranged in a randomized blocks and a factorial scheme of two soils and six levels of mined gypsum equivalent to 25, 50, 75, 100, 125 and 150% of gypsum requirements of the soil determined by Schoonover M-1 laboratory method, incorporated to the first 5 cm of the soil column, with three replications. The evaluated components were the electrical conductivity, the sodium adsorption ratio (SAR) and the soluble cations of the saturation extract. The level of gypsum equivalent to 100% of the gypsum requirement showed to be most effective at reducing the SAR of the extract, reducing soil contents of sodium in the soil.

Aplicacao de gesso e calcario na recuperacao de solos salino-sodicos do Estado de Pernambuco

An experiment was carried out in soil columns with the objective of evaluating the effect of application of gypsum and limestone on reclamation of the saline-sodic soils in the Irrigation district of Custodia, PE. The treatments were arranged in a randomized block design in a factorial scheme of four soils, two methods for applications of gypsum and gypsum plus limestone (applied on surface and incorporated into the first five cm of the soil column), two combinations of the chemical amendments (100% gypsum plus 0% limestone and 80% gypsum plus 20% limestone), calculated on the basis of gypsum requirement of soil and four granulometry gypsum strips (2.0-1.0; 1.0-0.5; 0.5-0.3 and < 0.3 mm) with three replications. The gypsum amount determined by the method of Schoonover M-1, under laboratory conditions, shows to be adequate in the displacement of the exchangeable sodium of the soil exchange complex. The efficiency of the gypsum as well as the gypsum plus lime mixture in reclamation of the soils shows to be superior, when the amendments are incorporated into the first 5 cm of the soil columns. Among the gypsum granulometry, the finest fractions, (0.5-0.3 mm and < 0.3 mm), presented better performance in replacing the exchangeable sodium of the exchange complex.

Ponto de murcha permanente fisiológico e potencial osmótico de feijão caupi cultivado em solos salinizados

Com o objetivo de avaliar o ponto de murcha permanente fisiologico, a umidade foliar e o potencial osmotico no feijoeiro caupi, sob duas condicoes de estresses (salino e salino + hidrico), foram conduzidos dois experimentos em casa de vegetacao na Universidade Federal Rural de Pernambuco (Recife, PE, Brasil). O delineamento experimental adotado foi o inteiramente casualizado, em arranjo fatorial 2 x 4, sendo duas classes texturais de solos (franco-arenoso e franco-argiloso) e quatro niveis de salinidade do solo, equivalentes as condutividades eletricas do extrato de saturacao do solo 4, 8 e 12 dS m

Comportamento hídrico e crescimento do feijão vigna cultivado em solos salinizados

Soil salinization reduces the capacity of plants to absorb water, and in general causes decrease in plant growth. Plant responses to salt stress are better correlated with osmotic potential compared to electrical conductivity of soil saturation extract. In order to evaluate the effect of salt stress on growth, water use and leaf osmotic potential of cowpea [Vigna unguiculata L. (Walp.)], an experiment was carried out in a greenhouse of the Federal Rural University of Pernambuco (Recife-PE, Brazil). The Treatments were in a factorial arrangement of 2 x 4, comprising of two soil textures and four levels of soil salinity (4, 8 and 12 dS m-1 at 25 °C, and the control without salt addition) with five replications. It was concluded that soil salinity causes reduction in water consumption, leaf osmotic potential, plant height, number of leaves and dry biomass of shoot of cowpea.

Características físicas de solos salino-sódicos do semiárido pernambucano em função de diferentes níveis de gesso

This study aimed to evaluate the efficiency of application of different levels of gypsum requirement on physical characteristics of saline-sodic soils of the region of semiarid of Pernambuco. The study was conducted in the Laboratory of Soil Mechanics and Waste Utilization of the Federal Rural University of Pernambuco. Treatments were arranged in a randomized block design with a factorial arrangement of two soils (S1 and S2) and five levels of gypsum requirement (50, 100, 150, 200 and 250%) determined by the method of Schoonover M-1, incorporated in the first 12.5 cm of the soil column, with five replications. The use of increasing levels of gypsum for the correction of saline-sodic soils provided greater water infiltration rate of the soil. The level of 100% of the gypsum requirement promoted lower degree of dispersion and more stability of soils aggregates. During the experiment it was observed that from the level of 150% of gypsum requirement occurred loss of colloids (mineral and/or organic).

Incorporação de gesso para correção da salinidade e sodicidade de solos salino-sódicos

Aiming to evaluate the effect of gypsum on the modification of chemical properties of saline-sodic soils collected in the Irrigated Perimeter of Ibimirim-PE, an experiment was carried out in soil columns installed at the Soil Mechanics and Residue Recovery Laboratoy at the Universidade Federal Rural de Pernambuco. The treatments were arranged in a completely randomized design with factorial arrangement of two soils (S1 and S2) and seven levels of gypsum requirement (50, 75, 100, 125, 150, 175 and 200%) determined by the Laboratory Method Schoonover-M1. The gypsum was incorporated in to the soils, in three replications, totaling 42 experimental units. The parameters evaluated were: electrical conductivity (EC), soluble cations and sodium adsorption ratio (SAR) in the saturation extract of soil. The level of the 100% of gypsum requirement caused decreased in sodicity values of SAR under 13 (mmol L-1)1/2, presenting itself as an effective method in reducing the levels of sodium in areas affected by salt. The water depth equivalent to three times of the volume of pores (3VP) decreased the EC of saturation extract to values < 4 dS m-1, being so indicated for soil salinity correction.

Growth of cowpea plants inoculated with Rhizobium in a saline-sodic soil after application of gypsum

Two experiments were carried out with the aim of evaluating the growth of cowpea cultivated in saline-sodic soils corrected with gypsum: one experiment in the laboratory, to identify the best level of gypsum for the correction of the saline-sodic soils of the state of Pernambuco, Brazil; and the other in a greenhouse, after correction of the soils. As the test plant, the cowpea cultivar pele de moca, inoculated with Rhizobium strain BR3267 was used. The experiments were arranged in a randomised block design in a 2 x 5 factorial arrangement, two soils and five levels of the gypsum requirement (GR), equivalent to 50, 100, 150, 200 and 250% of the GR of the soil, as determined by the Schoonover M-1 method, with five replications. The following were evaluated: electrical conductivity of the soil saturation extract (EC), soil exchangeable sodium and percentage of soil exchangeable sodium (ESP), number of nodules (NN), nodule dry weight (NDW), shoot dry weight (SDW), shoot height (PH) and nitrogen concentration (N) in the shoots. Application of 100% of the GR, followed by the enough water for leaching, was effective for the correction of soil sodicity. The application of increasing levels of soil GR resulted in an increase in the number of nodules, dry weight of the nodules and shoots, and the height and levels of N absorbed by the plants in soil S2. In soil S1, the use of levels of 200 and 250% of soil the GR caused a decrease in all the variables under study.

Dispersão de argilas em solos afetados por sais

To estimate clay dispersion the water dispersible clay is determined in the laboratory. This analysis may not correspond to reality in saline and saline-sodic soils, with high concentrations of salts in the solution. In this context, the dispersed clay was determined, using solutions of different electrical conductivities (0; 0.3; 0.6; 0.9 and 1.2 dS m-1) in seven representative soils of the State of Pernambuco, with the exchangeable-sodium-percentage adjusted in the range of 5-30%. The results showed that there was an increase of dispersed clay directly related to the increase in the exchangeable sodium percentage and the decrease of the electrical conductivity of the solution. The response to treatments was more pronounced in soils with higher proportions of more active clays compared to those with more iron oxides. The determinations of the water dispersible clay are accomplished with deionized or distilled water. However, in soils affected by salts, it is concluded that the determinations should be carried out with solutions of electrical conductivity different from 0 dS m-1 using solutions with values similar to those determined in the saturation extract.

Uso de resíduos de gesso como corretivo em solo salino-sódico

One of the hugest problems faced by the civil construction sector is the final destination of residues, especially gypsum, which presents recycling restrictions. However, these residues present a high amount of calcium in their composition, and can be alternatively used for replacing mined gypsum as a saline-sodic soil corrective. This study aimed at evaluating the efficiency of gypsum residues from the civil construction, when compared to mined gypsum, for correcting a saline-sodic soil. A randomized blocks design was used, in a factorial arrangement consisting of two kinds of corrective (gypsum residue and mined gypsum) and five leaching depths (0.5, 1.0, 1.5, 2.0 and 2.5 times the soil pores volume), with three replications. Electric conductivity, soluble cations and sodium adsorption ratio were evaluated in the soil saturation extract. The use of gypsum residue proved to be effective in leaching salts and soluble sodium in saline-sodic soil, and can be recommended as a calcium source for recovering from sodicity.