Vanderlei Rodrigues da Silva

Suscetibilidade à compactação de um latossolo vermelho-escuro e de um podzólico vermelho-amarelo

Soil compaction of the agricultural soils is a result of soil machine interactions, which influence physical and biological soil properties and their relations with crop growth and yield. The objective of this study was to determine the compression index, the preconsolidation pressure and the soil strain of a Haplortox (LE) and a Paleudalf (PV), with different initial state of compaction and water saturation. Undisturbed soil samples were collected in two soils and at two depths, at no tillage and conventional tillage, at several locations and different times to obtain a natural variation of bulk density, corresponding to different initial levels of compactness and water saturation. For the uniaxial compression test, successive static loads of 12.2; 25; 50; 100; 200; 400 and 800 kPa were used, during five minutes for each load. This was determined at previous tests, where 99% of the soil strain had occurred at the time. Soil strain showed differentiated behaviors for each soil. For soil Haplortox, under low water saturation ( 60%) water saturation, whereas for the intermediate saturation (30 to 60%) the model was linear. The compression index correlated negatively with the initial bulk density and with water saturation in PV. For high initial bulk density (> 1.45 Mg m-3), the Haplortox had greater susceptibility to compaction when water saturation was near 70%, whereas when the same soil had low compaction (bulk density < 1.30 Mg m-3), the major susceptibility occurred under lower water saturation (near 50%). Multiple regression equations for preconsolidation pressure, using initial bulk density and water saturation, had low determination coefficient (0.28 for PV and 0.32 for LE), although significant, which indicates the need for incorporation of more variables in these models.

Densidade do solo, atributos químicos e sistema radicular do milho afetados pelo pastejo e manejo do solo

A integracao lavoura-pecuaria e uma alternativa de renda dos produtores no sul do Brasil. Entretanto, o pisoteio animal e, ou, o preparo de solo podem compacta-lo, prejudicando o crescimento radicular e a produtividade das plantas. Estudaram-se os efeitos do pisoteio animal em regime de pastejo continuo durante o inverno/primavera e do impacto do plantio direto e do preparo convencional de solo no estado de compactacao, atributos quimicos e distribuicao radicular. Em Podzolico Vermelho-Amarelo de textura superficial franca, foi implantada uma pastagem de estacao fria composta por aveia (Avena strigosa Schreb) e azevem (Lolium multiflorum L.). A carga animal variou conforme o crescimento da pastagem. Em dezembro de 1996, foi implantada a cultura do milho (Zea mays L.) para a producao de silagem, usando os seguintes tratamentos: plantio direto na area nao pastejada, plantio direto apos o pastejo, preparo convencional de solo na area nao pastejada e preparo convencional de solo apos pastejo. As avaliacoes apresentadas neste estudo sao referentes ao terceiro ano de cultivo, no qual houve um periodo de pastejo de 107 dias. Aos 45 dias da emergencia do milho, foram abertas trincheiras (100 x 40 cm) para visualizar a distribuicao do sistema radicular e coletar amostras de solo, a cada 5 cm, para caracterizacao quimica e determinacao da densidade do solo e de raizes. Ao longo do perfil (0-40 cm), o desenho da distribuicao de raizes indicou maior quantidade de raizes no preparo convencional de solo, concordando com os resultados de densidade de raizes. O pisoteio animal nao teve efeito sobre as caracteristicas fisicas, possivelmente pelo fato de o residuo da pastagem permanecer proximo a 1,0 Mg ha-1 de materia seca. A densidade do solo no plantio direto, na camada de 5-10 cm, foi de 1,41 Mg m-3, tanto na area pastejada como na nao pastejada. No preparo convencional de solo, esses valores foram de 1,15 Mg m-3, na area pastejada e de 1,12 Mg m-3, na area nao pastejada. A produtividade de graos de milho (4,55 Mg ha-1) e de silagem (34,66 Mg ha-1) nao foi afetada pelo pastejo ou pelo preparo do solo. O sistema de manejo do solo teve maior influencia na densidade do solo do que o pisoteio animal, considerando o controle da carga animal ajustado ao crescimento da pastagem.

Soil strength as affected by combine wheel traffic and two soil tillage systems

A resistencia mecânica do solo a penetracao pode limitar o crescimento do sistema radicular e a produtividade das plantas. O estudo objetivou avaliar a resistencia mecânica do solo a penetracao nas zonas de trafego e entre trafego de uma colhedora de graos, em dois sistemas de manejo do solo e duas condicoes de umidade do solo. Os tratamentos foram: plantio direto, nao trafegado pelas rodas da colhedora e no rastro do pneu dianteiro da colhedora; na area com preparo do solo, nao trafegado pelas rodas da colhedora e no rastro do pneu dianteiro da colhedora. Determinaram-se a resistencia mecânica do solo a penetracao com um penetrografo, realizando leituras eletronicas de resistencia a cada 0,15cm de profundidade, e a umidade do solo, ate uma profundidade de 40cm, em duas condicoes de umidade do solo (seco e umido), num Latossolo Vermelho-Escuro, argiloso. Nesses mesmos locais, foram coletadas amostras para determinacao da umidade do solo. O peso distribuido no eixo dianteiro da colhedora foi de 5,0Mg, sendo a area de contato com o solo igual a 0,283m2, exercendo uma pressao de contato com o solo de 0,0884MPa. Com maiores conteudos de agua no solo, a resistencia mecânica a penetracao foi baixa (menor que 2MPa) entre os diferentes tratamentos, nao limitando o crescimento radicular. Porem, na segunda avaliacao, quando o solo estava mais seco, verificou-se que o trafego da colhedora causou compactacao na camada de 5 a 17cm. O conteudo de agua do solo influenciou os valores absolutos de resistencia mecânica a penetracao. Valores de resistencia mecânica a penetracao considerados como criticos ao desenvolvimento das plantas (maiores que 2,0MPa) foram observados, principalmente, para o sistema de plantio direto. Os maiores valores de resistencia a penetracao foram encontrados no sistema de plantio direto que apresentou maior estado de compactacao na camada de 7,5 a 17,0cm. O sistema de plantio direto possui um estado de compactacao mais elevado, causado pelo acumulo de pressoes mecânicas a que o solo e submetido anualmente. Entretanto, a produtividade da cultura da soja nao diferiu entre os sistemas de manejo do solo, permanecendo em torno de 3,15Mg ha-1.

Variabilidade espacial da resistência do solo à penetração em plantio direto

The objective of this work was to characterize the spatial variability of soil resistance to penetration (RP) in no tillage farming, identifying the degree of soil compaction. The RP was determined directly in the field, in systematic way in three soils types. The first experimental area was in Santa Maria, in Hapludalf, with 120g clay kg-1 in the layer of 0-20cm. The second, located in Cruz Alta, in a Haplortox, with 500g clay kg-1 in the 0-20cm layer and the third experimental area located in Colonel Barros, in a Hapludox, with 600g clay kg-1 in the 0-20cm layer. The values of RP were analyzed by descriptive statistics and for geoestatistical techniques. In the three soils, the technique of the krigeagem was used to make surface maps, identifying three classes of RP, the one that, we called degree compaction (EC). In Hapludalf, smallest EC was considered the values of RP among 0.58MPa to 0.88MPa, the middleman EC among 0.89MPa to 1.18MPa and largest EC, values of RP between 1.19MPa and 1.50MPa. In Haplortox, in the smallest EC the values of RP were selected varying among 1.70MPa to 2.22MPa, the middleman EC, RP among 2.23MPa to 2.75MPa and, in largest EC, values of RP among 2.76MPa to 3.20MPa. In Hapludox the values of RP in smallest EC were among 0.20MPa to 1.59MPa, in the middleman EC among 1.60MPa to 2.10MPa and in largest EC, among 2.11MPa to 2.80MPa. In the three areas, the distribution of the soil degree compaction decreased of the headboard area (larger EC) for the center of the farming (smaller EC).

Atributos físicos e rendimento de grãos de trigo, soja e milho em dois Latossolos compactados e escarificados

Soil compaction affects structural quality in areas under no-tillage systems and reduce crop yield, particularly in clayey soils. The objective of this study was to evaluate the impact of three compaction states on crop yield and soil physical attributes in two Oxisols under no-tillage and chiseling. The soil bulk density (Ds), soil resistance to penetration (Rp) and crop yield of the wheat, soybean and corn were determined. One Oxisol (LVd) has 550g kg -1 of clay and other (LVdf) 610g kg -1 clay, located in Rio Grande do Sul plateau. The experiment was run from 1999 to 2001 in a commercial crop field mapped with respect to soil resistance to penetration. Three states of compaction were separated and mapped: a) EC1- higher compaction state located at the head of crop site; b) EC2medium state of compaction and; c) EC3 lower state of compaction toward central part of the site. To serve as no compacted area a plot was chiselled. The highest values of Ds (1.62 e 1.54Mg m -3 ) and Rp (3.4 e 3.8MPa), respectively for LVd and LVdf, cultivated under no-tillage system, were found in the layer of 0.07-0.12m. The systematic mobilization by chiseling mechanisms of the planters reduced Ds in 26% on LVd e 15% on LVdf, compaction in the layer of 0.00-0.05m in relation the depth of 0.07-0.12m. The highest soil compaction state (EC1) in relation the lower state of compaction (EC3) in the two Oxisols decreased crop yield of wheat in 18% and 34%, respectively for LVd e LVdf and corn in 24% on LVdf, but not of soybean. The soil chiseling increased corn and wheat grain yield in relation to the three states of soil compaction.

Nonpoint source pollution by swine farming wastewater in bean crop

In order to verify the environmental impact of the application of swine farming wastewater in bean crop, an experiment was set up in the Experimental Farm of PUCPR - Toledo, PR, Brazil. Runoff and soil samples were collected at the end of the experiment. Four wastewater treatments were utilized during the experiment (50, 100, 150 and 200 m3 ha-1) and the without wastewater as the control. The results demonstrate that (i) the amounts of potassium, phosphorus, and nitrogen in runoff are exponential, (ii) that phosphorus has a seven-fold polluting potential compared to potassium and three-fold compared to nitrogen, and (iii) that the mobility of potassium in the soil profile is the largest, followed by those of nitrogen and phosphorus.

Variabilidade espacial de Planossolo e produtividade de soja em várzea sistematizada: análise geoestatística e análise de regressão

Spatially-defined soil and plant properties contribute to better planning of experiments and commercial fields. This research had as objective the study of spatial variability of some physical and chemical properties of the soil and their relationship with soybean productivity. The experiment was conducted in the agricultural year of 2000, at the Federal University of Santa Maria, RS, Brazil, on land-leveled paddy soil. An area of 160 x 88m was sampled at an interval of 8 x 8m, resulting in 240 sampling points. The plant properties studied were soybean yield and plant height. Several chemical and physical properties of the topsoil (0 to 0.15m) and subsoil (0.15 to 0.30m) were determined. Geostatistical analysis was done only for the soil layer that presented correlation with the plant properties (0-0.15m), and the space dependence of the attributes was evaluated by scaled semivariograms. Except for soybean production, particle density and flocculation degree, all soil properties presented moderate (0.64 to 0.75) to strong (>0.75) space dependence. The production of soybean was influenced by space variability of the analyzed soil properties. The spatial variability of the soil physical and chemical properties in land-leveled paddy soil affected the production of soybean. The properties were classified in two different categories, based on semivariogram model and range: (i) exponential model and range smaller than 40m and (ii) gaussian model and range smaller than 67m. A gaussian model with range smaller than 45m described the spatial variation of soybean yeild.

Soil water dynamics related to the degree of compaction of two brazilian oxisols under no-tillage

Soil water properties are related to crop growth and environmental aspects and are influenced by the degree of soil compaction. The objective of this study was to determine the water infiltration and hydraulic conductivity of saturated soil under field conditions in terms of the compaction degree of two Oxisols under a no-tillage (NT). Two commercial fields were studied in the state of Rio Grande do Sul, Brazil: one a Haplortox after 14 years under NT; the other a Hapludox after seven years under NT. Maps (50 x 30 m) of the levels of mechanical penetration resistance (PR) were drawn based on the kriging method, differentiating three compaction degrees (CD): high, intermediate and low. In each CD area, the infiltration rate (initial and steady-state) and cumulative water infiltration were measured using concentric rings, with six replications, and the saturated hydraulic conductivity (K(θs)) was determined using the Guelph permeameter. Statistical evaluation was performed based on a randomized design, using the least significant difference (LSD) test and regression analysis. The steady-state infiltration rate was not influenced by the compaction degree, with mean values of 3 and 0.39 cm h-1 in the Haplortox and the Hapludox, respectively. In the Haplortox, saturated soil hydraulic conductivity was 26.76 cm h-1 at a low CD and 9.18 cm h-1 at a high CD, whereas in the Hapludox, this value was 5.16 cm h-1 and 1.19 cm h-1 for the low and high CD, respectively. The compaction degree did not affect the initial and steady-state water infiltration rate, nor the cumulative water infiltration for either soil type, although the values were higher for the Haplortox than the Hapludox.

Critical limits of soil penetration resistance in a rhodic Eutrudox

Soil penetration resistance is an important indicator of soil physical quality and the critical limit of 2 MPa has been widely used to characterize the soil physical quality, in both no-tillage and conventional systems. The aim of this study was to quantify the influence of different tillage and cropping systems on the soil penetration resistance in a Rhodic Eutrudox. The experiment was carried out in a 5 × 2 factorial, completely randomized block design (tillage systems vs cropping systems), with four replications. The tillage systems consisted of: conventional tillage disk harrow; minimum tillage with annual chiseling; minimum tillage with chiseling every three years; no-tillage for 11 consecutive years; and no-tillage for 24 consecutive years. The factor cropping systems was represented by: crop rotation and crop succession. The soil penetration resistance (SPR) was determined in 20 soil samples per treatment and layer (0.0-0.10; 0.10-0.20 and 0.20-0.30 m) for each soil matric potential: -6, -10, -33, -100, -500 kPa. The SPR was determined at a volumetric soil water content equivalent to the fraction of plant-available water of 0.7. There were no differences of soil penetration resistance between the two cropping systems. Differences in soil penetration resistance among tillage systems were related to the matric potential at which the samples were equilibrated. The critical SPR limit of 2 MPa normally used for conventional tillage should be maintained. However, this value of 2 MPa is inappropriate for the physical quality characterization of Rhodic Eutrudox under no-tillage and/or minimum tillage with chiseling. Regardless of the cropping systems, the critical SPR limit should be raised to 3 MPa for minimum tillage with chiseling and to 3.5 MPa for no-tillage.

Variabilidade espacial de propriedades físico-hídricas do solo, da produtividade e da qualidade de grãos de trigo em Argissolo Franco Arenoso sob plantio direto 1

Spatial varibility of soil physico-hydrical properties is related to soil genesis and management, and affect crop production. The objectives of this study were to identify and to relate spatial variability of saturated hydraulic condutivity (K(qs)), soil mechanical resistance (R), soil texture, and A horizont depth, of a Typic Hapludalf under no-till, with wheat yield and hectoliter weight. This experiment was conducted in the winter of 1999, on a 1.51 ha no-till wheat field. Soil and plant characterization was done on five transects with 100m in the East-West direction, with sampling points 10m apart. Values of R for the depths of 5cm, 7.5cm, 10cm and 15cm and A horizont depth showed normal distribution. Spherical model semivariograms were adjusted for K(qs), R in the 30cm depth, clay content, and A horizont depth. Exponential model for R in the 2.5cm and 5cm depths, clay and silt content, and wheat yield and hectoliter weight. For the 7.5cm, 10cm, 12.5cm, 15cm and 17.5cm depths, R semivariograms showed pure nugget effect; in these depths the machinery traffic and previous soil management effects are prominent. Wheat yield and hectoliter weight did not correlate with K(qs) and R. When evaluating the spatial variability in R for soil layers deeper than 5cm, the distance between samples points should be smaller than 10m.