Vilson Antonio Klein

DENSIDADE E DISTRIBUIÇÃO DO DIÂMETRO DOS POROS DE UM LATOSSOLO VERMELHO, SOB DIFERENTES SISTEMAS DE USO E MANEJO

Toda acao antropica ocasiona alteracoes no ambiente. Estudar as alteracoes que o manejo do solo para fins agricolas provoca nas propriedades fisicas de um Latossolo Vermelho constituiu o objetivo deste trabalho. Amostras de solo com estrutura indeformada foram coletadas ao longo do perfil, ate 1 m de profundidade, em tres sistemas de uso e manejo: mata, sequeiro e irrigado. Essas foram submetidas a diferentes tensoes para determinar a curva de retencao de agua e para avaliar a distribuicao do diâmetro dos poros. No campo, determinou-se a porosidade de aeracao em periodos subsequentes a inundacao de uma parcela, em relacao a porosidade total do solo calculada. Os resultados indicaram que o manejo influiu na densidade do solo ate a profundidade de 0,4 m e, em consequencia dessas alteracoes, foram afetadas a distribuicao do diâmetro dos poros e a porosidade de aeracao; verificou-se que densidades superiores a 1,2 Mg m-3 acarretaram deficiencia na aeracao do sistema radicular por um periodo superior a 24 h.

Rendimento da soja e intervalo hídrico ótimo em latossolo vermelho sob plantio direto escarificado

O intervalo hidrico otimo (IHO) e um metodo que integra varios fatores que afetam o desenvolvimento das plantas, e corresponde ao intervalo de umidade do solo no qual nao ocorre restricao de aeracao (porosidade de aeracao minima de 0,10 m3 m-3) nem de resistencia mecânica a penetracao das raizes (RP) dentro da faixa de agua disponivel as plantas, isto e, entre a capacidade de campo (CC) e o ponto de murcha permanente (PMP). O objetivo deste trabalho foi determinar o IHO em um Latossolo Vermelho sob plantio direto (PD) e plantio direto escarificado (PDE), bem como o rendimento de graos de soja. Avaliou-se a densidade do solo, o IHO, a variacao da umidade do solo durante o ciclo da soja e o rendimento de graos. Os resultados indicaram que a densidade do solo foi menor no PDE, o que acarretou maior amplitude do IHO. A densidade critica, na qual IHO = 0, foi semelhante entre o PD e o PDE. Durante o ciclo da cultura da soja, em varios momentos, a sua umidade ficou fora do IHO, quando assumida RP limitante de 2 MPa. Como o rendimento de graos da soja nao apresentou diferenca significativa, deduz-se que a RP de 2 MPa nao e limitante para a soja.

Água disponível em um Latossolo Vermelho argiloso e murcha fisiológica de culturas

To estimate available soil water to plants it is necessary to measure field capacity (FC) and permanent wilting point (PWP). The objective of this study was to compare soil moisture at FC and PWP measured by different methods. The soil used was a tropical Oxisol (Haplorthox). The FC was measured under field conditions, using the internal drainage method and in laboratory using porous plate funnel. The PWP was quantified in laboratory as the soil moisture at -1.5 MPa matric potential measured by pressure plate apparatus (Richards chamber) and by WP4 dewpoint Potentia Meter. The physiological PWP was measured using corn and sunflower plants, when they had three leaf pairs and showed irreversible wilting. The soil moisture for PWP based on the physiological method was smaller than soil moisture measured with the pressure plate apparatus; however, soil moisture for sunflower wilting was similar while for corn it was greater than that obtained with the WP4. The available water decreased with increase in water tension considered for estimating FC and with the WP4 method, but similar to one quantified with the physiological method. Thus, the WP4 allowed for adequate estimation of PWP and available water to plants in a clay soil.

Avaliação de diferentes manejos de solo e métodos de semeadura em área sob sistema de plantio direto

Aiming to evaluate the response of corn to different soil tillage systems and seeding methods under no tillage, a field trial was conducted at the Faculdade de Agronomia da Universidade de Passo Fundo, RS, in 1993-94. Four treatments (no tillage system; disk plow + disking; chisel plow + disking and prototype chisel plow) and two seeding types (hoe type planter and offset double disk) were used. Grain yield of com and soil density were evaluated after corn harvesting. Corn yield was significantly affected by hoe type planter, mainly for the no till treatment. The soil density results showed more compaction on the surface layers on the no tillage treatment, howewer no difference among treatments was observed for deeper soil layers. It was concluded that narrow knife used on the planter eliminates soil compaction problems, proportioning better rooting of plante.

Propriedades físico-hídricas do solo sob plantio direto escarificado e rendimento da soja

Under no-tillage (NT) system, the soil is susceptible to changes in its structure caused by minimum soil disturbance and machine traffic. The effect of these changes on plant growth depends on climatic conditions. Sporadic soil chiseling under the NT system has been used as an option to minimize the effects of soil compaction, particularly in periods of water shortage. The aim of the present study is to analyze the changes in the soil physical and hydraulic properties under the NT system and the chiseled no-tillage (CNT) system, as well as the effect of two types of no-till drills on soybean yield. This experiment was carried out in an area in which NT had been used for six years and part of which had been chiseled. Organic matter content, bulk and particle density, relative density, soil mechanical resistance to penetration, soybean yield components, and soybean grain yield were evaluated. The results indicated that soil chiseling under NT does not affect soil organic matter content and decreases bulk and particle density, relative density, and soil mechanical resistance to penetration. Soybean grain yield components were not affected by soil management or by the use of seed drills. Soybean grain yield was not affected by soil management, but was positively affected by the use of hoe-type drills under NT.

Faixa de umidade menos limitante ao crescimento vegetal e sua relação com a densidade do solo ao longo do perfil de um latossolo roxo

When a soil is managed, its structure is affected, usually increasing the bulk density, decreasing the porosity and modifying the distribution of porous diameter distribution. This investigation was carried out with the objective of evaluating the effect of soil bulk density on water availability to the plants. The experiment was conducted in Guaira (SP), Brazil in an Oxisol (typic Acrorthox). Three adjacent areas under different management systems were selected: no-tillage-non-irrigated, no-tillage-irrigated and natural forest. Undisturbed soil samples were collected at soil depth increments of 0.1m up to 1.0m depth. These samples were submitted to different tensions to determine the water retention and, subsequently the penetration resistance. The least limiting water range concept was used, to calculate the available water, which is based not only on field capacity and permanent wilting point, but also on the limiting resistance to penetration and the limiting aeration porosity. Results indicated that the increase of the soil bulk density up to 1.11Mg m-3, increases the soil water storage and also the available water to the crops; higher values of bulk density decrease the soil water availability.

Textura do solo e a estimativa do teor de água no ponto de murcha permanente com psicrômetro

The determination of the available water to plants is essential to right irrigation management and definition regarding the use in agricultural soils. The main factors that exert influence on retention and availability of water to plants are texture and soil structure. The aim of this study was to quantify the influence of the texture on water retention in the condition of permanent wilting point (PWP) of plants (-1,5MPa) using a WP4-T Dewpoint Potentia Meter. The texture of 100 soil sample and soil moisture at PWP was determined. Results indicated that, in potentials higher than -1,0MPa, WP4-T seemed not very precise, therefore its use is not recommended in this condition. PWP increased from 0,059 to 0,29g g-1, while the clay content increased from 120 to 779g kg-1. It was obtained a good adjustment of the results of water content at PWP based on clay content of soil, being that 91% of variation in water content at PWP could be attributed to variation in clay content. It was concluded that WP4-T is an equipment that can be used to determine PWP and the equation PWP (g g-1)=0,0003 * Clay(g kg-1)+0,0118 can be used to estimate PWP.

Indicadores da qualidade física de um Latossolo Vermelho distrófico típico sob plantio direto escarificado

The assessment of the physical quality of agricultural soils has taken on added importance, especially in areas under no tillage, as important changes to soil structure occur as a result of this type of management. Soil resistance to penetration (RP), the least limit water range (LLWR) and relative density (RD) have been used as evaluation parameters. The aim of this study was to assess and model RP as a function of soil moisture and density and to determine the LLWR as a function of RD under two management systems. Samples of soils under no tillage (NT) and chiseled no tillage (CNT) for six months and whose structure had been preserved were collected at a depth of 0 to 5cm. In the laboratory, RP was assessed using an electronic penetrometer and each management system was statistically adjusted to Busscher’s equation. In CNT soils, RP was lower for the same density and moisture, and lower than the PD, whereas the difference in RP was larger between the two management systems when soil moisture in the field was lower. The LLWR was higher under CNT up to an RD of 0.9. Results allow us to conclude that RP is a sensitive parameter for determining the physical quality of the soil and that CNT significantly reduced RP and increased the LLWR, providing favorable conditions for root growth for a longer time period.

Crescimento de mudas de gipsofila em diferentes substratos

Floriculture is one of the branches in horticulture that has expanded in the last years because of its profitability. The study and the use of substrates for producing young plants are important, once the gypsophila production depends on young plants quality. Considering that the quality of a substrate is the result of its chemical and physical properties, the characterisation of these properties was made. This trial was carried out to evaluate the growth of Gypsophila paniculala cv. Bristol Fairy plants in different substrates. The experimental design was a randomised complete blocking split-plot scheme with six treatments (substrates) and four replicates. Each plot consisted of 22 plants, totalizing 588 young plants. The following physical chemical analyses were performed: dry density, total porosity, aeration space, available water, water easily available, pH, electric conductivity and cations capacity change. Plant development was evaluated on a weekly basis and the following parameters were measured: survival rate, root volume, fresh and dry matter of aerial part and root. Substrates with higher levels of water easily available optimised the Gypsophila paniculata acclimatization. The best results for young plants production were obtained with the substrates FE1(perlite + peat) and FE4 (pine of husks + perlite + peat).

Matéria orgânica e atributos físicos de um Latossolo Vermelho após aplicações de dejeto de suínos

Swine farming generates great amount of manure that can be used as fertilizer in crops and pastures. The continuous application of swine waste may change the physical attributes of the soil. The present study aimed to verify the influence of 0, 48, 96, 144, 192 and 240 m3 ha-1 year-1 of pig slurry applications in a four-year time span on Oxisol in a perennial pasture. The mean content of dry matter in pig slurry was 1.72%. Soil samples of undisturbed and disturbed structures were collected in 0-0,05; 0,05-0,10; 0,10-0,15; 0,15-0,20; 0,20-0,25;0, 25-0,30 m layers. Organic matter content, texture, water dispersible clay, soil density, maximum bulk density, relative density, mechanical resistance to penetration, total porosity and macro, micro and criptopores volume, soil permeability to air, soil aggregates stability were evaluated. Organic matter content was the only attribute to show some interaction between dose and layer. The evaluated parameters were not influenced by application of different doses of pig slurry with dry matter of 1.72% for a period of four years in an Oxisol.