Índice de cone, capacidade de suporte de carga e teor de água de quatro solos da Fazenda Lageado, Botucatu/SP : correlações r mapas de isocompactação

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Métodos probabilístico e determinístico para diagnóstico da necessidade de subsolagem de solos agrícolas

This paper presents two techniques to evaluate soil mechanical resistance to penetration as an auxiliary method to help in a decision-making in subsoiling operations. The decision is based on the volume of soil mobilized as a function of the considered critical soil resistance to penetration in each case. The first method, probabilistic, uses statistical techniques to define the volume of soil to be mobilized. The other method, deterministic, determines the percentage of soil to be mobilized and its spatial distribution. Both cases plot the percentage curves of experimental data related to the soil mechanical resistance to penetration equal or larger to the established critical level and the volume of soil to be mobilized as a function of critical level. The deterministic method plots showed the spatial distribution of the data with resistance to penetration equal or large than the critical level. The comparison between mobilized soil curves as a function of critical level using both methods showed that they can be considered equivalent. The deterministic method has the advantage of showing the spatial distribution of the critical points.

Penetration resistance in a latosol under different moisture and penetration speeds

The soil penetration resistance has been used to represent the compaction situation and several authors have attempted to relate the cone index (CI) with the bulk density. The importance of using the CI as source of information for decisions in agricultural activities, livestock and forestry manner, has become increasingly larger, which requires more knowledge about the penetrometers and penetrographs behavior. This study aimed to verify, in controlled laboratory conditions, the influence of soil water content and cone penetration rate to obtain the cone index, when density variation occurs. The soil was compacted by compression through a universal press cylinder which was specially designed to produce the test specimens. Bulk densities were determined from samples taken from the test specimens and their moisture content. The CI values obtained were between 0.258 and 4.776 MPa, measured in 4 moistures and 7 soil densities with 3 penetration speeds. It was concluded that the determination of IC is strongly influenced by the soil moisture but the penetration speed variation, used in this study, was not sufficient to influence the IC determination. However, the decrease in soil water content may increase the sensitiveness to detect a variation in bulk density by the use of cone index.

Soybean root growth and crop yield in reponse to liming at the beginning of a no-tillage system

Analyzing the soil near crop roots may reveal limitations to growth and yield even in a no-tillage system. The purpose of the present study was to relate the chemical and physical properties of soil under a no-tillage system to soybean root growth and plant yield after five years of use of different types of limestone and forms of application. A clayey Oxisol received application of dolomitic and calcitic limestones and their 1:1 combination in two forms: surface application, maintained on the soil surface; and incorporated, applied on the surface and incorporated mechanically. Soil physical properties (resistance to mechanical penetration, soil bulk density and soil aggregation), soil chemical properties (pH, exchangeable cations, H+Al, and cation exchange capacity) and plant parameters (root growth system, soybean grain yield, and oat dry matter production) were evaluated five years after setting up the experiment. Incorporation of lime neutralized exchangeable Al up to a depth of 20 cm without affecting the soil physical properties. The soybean root system reached depths of 40 cm or more with incorporated limestone, increasing grain yield an average of 31 % in relation to surface application, which limited the effect of lime up to a depth of 5 cm and root growth up to 20 cm. It was concluded that incorporation of limestone at the beginning of a no-tillage system ensures a favorable environment for root growth and soybean yield, while this intervention does not show long-term effects on soil physical properties under no-tillage. This suggests that there is resilience in the physical properties evaluated.

Soil Compaction Curve of an Oxisol Under Sugarcane Planted After In-row Deep Tillage

ABSTRACT Soil tillage that maintains the productivity of sugarcane plantations, providing an area for the root development and without traffic on crop rows, has given rise to new technologies in rural areas. The purpose of this study was to evaluate the soil physical properties in two sugarcane plantations, one of which was prepared with deep tilling and the other with conventional tillage. The experiment was conducted in Lençóis Paulista, São Paulo State. Soil penetration resistance and relative density were analyzed. The cone index was lower in deep-tilled soil without traffic in all layers, than in deep-tilled soil with traffic and in conventional tillage. In both tillage treatments, the relative density values were acceptable in the 0.00-0.15 m soil layer, but considered detrimental for sugarcane development in the 0.15-0.30 and 0.30-0.45 m layers.

Correlation of physical and chemical attributes of soil with sugarcane yield

The objective of this work was to evaluate the correlation between sugarcane yield and some physical and chemical attributes of soil. For this, a 42‑ha test area in Araras, SP, Brazil, was used. Soil properties were determined from samples collected at the beginning of the 2003/2004 harvest season, using a regular 100x100 m grid. Yield assessment was done with a yield monitor (Simprocana). Correlation analyses were performed between sugarcane yield and the following soil properties: pH, pH CaCl2, N, C, cone index, clay content, soil organic matter, P, K, Ca, Mg, H+AL, cation exchange capacity, and base saturation. Correlation coefficients were respectively ‑0.05, ‑0.29, 0.33, 0.41, ‑0.27, 0.22, 0.44, ‑0.24, trace, ‑0.06, 0.01, 0.32, 0.14, and 0.04. Correlations of chemical and physical attributes of soil with sugarcane yield are weak, and, per se, they are not able to explain sugarcane yield variation, which suggests that other variables, besides soil attributes, should be analysed.

Development of an automated bench top electronic penetrometer

The aim of this study was to develop a an automated bench top electronic penetrometer (ABEP) that allows performing tests with high rate of data acquisition (up to 19,600 Hz) and with variation of the displacement velocity and of the base area of cone penetration. The mechanical components of the ABEP are: a supporting structure, stepper motor, velocity reducer, double nut ball screw and six penetration probes. The electronic components of ABEP are: a "driver" to control rotation and displacement, power supply, three load cells, two software programs for running and storing data, and a data acquisition module. This penetrometer presented in compact size, portable and in 32 validation tests it proved easy to operate, and showed high resolution, high velocity in reliability in data collection. During the validation tests the equipment met the objectives, because the test results showed that the ABEP could use different sizes of cones, allowed work at different velocities, showed for velocity and displacement, were only 1.3% and 0.7%, respectively, at the highest velocity (30 mm s-1) and 1% and 0.9%, respectively for the lowest velocity (0.1 mm s-1).

Spatial variability of soil penetration resistance influenced by season of sampling

O objetivo deste trabalho foi analizar a distribuição espacial da compactação do solo e a influência da umidade do solo na resistência à penetração. Esta última variável foi descrita pelo índice de cone. O solo estudado foi Nitossolo e os dados de índice de cone foram obtidos usando um penetrômetro. A resistência do solo foi avaliada a 5 profundidades diferentes, 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm e mais de 40 cm, porém o conteúdo de umidade do solo foi medido a 0-20 cm e 20-40 cm. As condições hídricas do solo variaram nas diferentes amostragems. Os coeficientes de variação para o índice de cone foram 16,5% a 45,8% e os do conteúdo de umidade do solo variaram entre 8,96% e 21,38%. Os resultados sugeriram elevada correlação entre a resistência do solo, estimada pelo índice de cone e a profundidade do solo. Sem embargo, a relação esperada com a umidade do solo não foi apreciada. Observou-se dependência espacial em 31 de 35 séries de dados de índice de cone e umidade do solo. Esta dependência foi ajustada por modelos exponenciais com efeito pepita variável de 0 a 90% o valor do patamar. em séries de dados o comportamento foi aleatório. Portanto, a técnica das distâncias inversas foi utilizada para cartografar a distribuição das variáveis que não tiveram estrutura espacial. Na krigagem constatou-se uma suavização dos mapas comparados com esses das distâncias inversas. A krigagem indicadora foi utilizada para cartografar a variabilidade espacial do índice de cone e recomendar melhor manejo do solo.

Estimation and evaluation of dynamic properties as indicators of changes on soil structure in sugarcane fields of São Paulo State - Brazil

The indiscriminate management and use of soils without moisture control has changed the structure of it due to the increment of the traffic by agricultural machines through the years, causing in consequence, a soil compaction and yield reduction in the areas of intensive traffic. The purpose of this work was to estimate and to evaluate the performance of preconsolidation pressure of the soil and shear stress as indicators of changes on soil structure in fields cropped with sugarcane, as well as the impact of management processes in an Eutrorthox soil structure located in São Paulo State. The experimental field was located in Piracicaba's rural area (São Paulo State, Brazil) and has been cropped with sugarcane, in the second harvest cycle. The soil was classified by Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA) [Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA), 1999. Centro Nacional de Pesquisa de Solos. Sistema Brasileiro de Classificao de Solos, Empresa Brasileira de Pesquisa Agropecuária (EMBRAPA), Brasilia, 412 pp.] as an Eutrorthox. Undisturbed samples were collected and georeferenced in a grid of 60 m x 60 m from two depths: 0-0.10 m (superficial layer - SL) and in the layer of greatest mechanical resistance (LGMR), previously identified by cone index (CI). The investigated variables were pressure preconsolidation (sigma(p)), apparent cohesion (c) and internal friction angle (phi). The conclusions from the results were that the SLSC was predicted satisfactorily from up as a function of soil moisture; thus, decisions about machinery size and loading (contact pressures) can be taken. Apparent cohesion (c), internal friction angle (phi) and the Coulomb equation were significantly altered by traffic intensity. The sigma(p), c and phi maps were shown to be important tools to localize and visualize soil compaction and mechanical resistance zones. They constitute a valuable resource to evaluate the traffic impact in areas cropped with sugarcane in State of São Paulo, Brazil. (C) 2008 Elsevier B.V. All rights reserved.

Avaliação do contato pneu-solo em três modelos de pneus agrícolas

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)

Produtividade da soja e resistência mecânica à penetração do solo sob sistema plantio direto no cerrado brasileiro

A resistência mecânica à penetração do solo pode influenciar, negativamente, o crescimento radicular da soja, afetando, sobremaneira, sua produtividade. No ano agrícola 2008/2009, no município de Selvíria (MS), no Cerrado brasileiro, foi analisada a produtividade da soja, em função da resistência mecânica à penetração de um Latossolo Vermelho distroférrico, no sistema de semeadura direta. O objetivo foi selecionar, entre os atributos pesquisados do solo, aquele com a melhor correlação, linear e espacial, para explicar a variabilidade da produtividade da soja. Foi instalada uma malha geoestatística, para a coleta de dados do solo e da planta, com 120 pontos amostrais, em área de 8,34 ha e declive homogêneo de 0,055 m m-1. Dessa forma, visando-se a auxiliar futuros trabalhos voltados à agricultura de precisão, os quais venham a utilizar os mesmos atributos do presente estudo, os valores dos alcances da dependência espacial a serem empregados deverão estar compreendidos entre 38,1 m e 114,7 m. do ponto de vista linear, a resistência mecânica à penetração do solo, quando avaliada na camada 0,10-0,20 m, apresentou boa correlação exponencial inversa com a produtividade de grãos de soja. Entretanto, do ponto de vista espacial, o número de vagens por planta apresentou-se como bom indicador da produtividade de grãos de soja.

Correlação linear e espacial entre o rendimento de grãos do feijoeiro e a resistência mecânica à penetração em um Latossolo Vermelho distrófico

A resistência mecânica à penetração apresentada pelo solo exerce grande influência sobre o desenvolvimento vegetal, uma vez que o crescimento das raízes, assim como o rendimento das culturas, varia de forma inversamente proporcional ao seu valor. No ano agrícola de 2001/2002, na Fazenda Experimental de Ensino e Pesquisa da Faculdade de Engenharia/UNESP - Campus de Ilha Solteira, foram analisados o rendimento de grãos do feijoeiro (PG) e a resistência mecânica à penetração (R), de um Latossolo Vermelho distrófico. O objetivo foi apurar diretrizes relacionadas com o aumento da produtividade agrícola em questão, estudando a correlação linear e a espacial entre a PG e a R. Foi instalada uma rede geoestatística para a coleta dos dados do solo e da planta, estabelecida com espaçamentos de 5 x 5 m e 2,5 x 2,5 m, que continham 120 pontos amostrais distribuídos numa área de 1.875 m². A correlação linear entre a PG e a R foi praticamente nula, uma vez que, dependendo das profundidades estudadas do solo, apresentou coeficientes de correlação (r) menores do que 0,20. A análise geoestatística apresentou boa estrutura de dependência espacial, tanto para a PG quanto para a R, quando analisadas isoladamente. Entretanto, a análise espacial conjunta de tais atributos apresentou-se inconsistente. Assim, com o aumento da resistência mecânica à penetração, em determinada região do solo ocorreu ora aumento, ora diminuição do rendimento de grãos do feijoeiro.

Avaliação da resistência do solo à penetração em diferentes solos com a variação do teor de água

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Performance of low/correct pressure radial ply tires

Extensive field testes were conducted using the UCD single wheel tester employing three large radial ply tractor tires in two different soils, four different soil conditions, two axle load levels, and three levels of tire inflation pressures in order to quantify the benefits of using low/correct inflation pressures. During these tests slip, net traction, gross traction, and dynamic axle load were recorded. Furthermore, soil moisture content, cone index, and dry bulk density data were obtained at test locations. The results of the analysis showed a significant increase in net traction and traction efficiency when low/correct inflation was used. Benefits of using low/correct pressure was higher in tilled soil conditions.

Correlação da produtividade do feijão com a resistência à penetração do solo sob plantio direto

The soil mechanical resistance to penetration (PR) has great influence on vegetative development as the root growth and the crop productivity change in inverse proportion. Thus, the objective of this research was to study correlation between the bean grain productivity and the PR in an Oxisol cultivated for four years in no-tillage system at FEIS/UNESP. The attributes PR and yield were determined in a regular grid with 119 sample points. The PR was determined in the layers of 0-0.05, 0.05-0.10, 0.10-0.15, 0.15-0.20 and 0.25-0.30 m. The results were submitted to procedures of descriptive statistics, linear correlation and geostatistic analysis. The linear correlation between the yield and PR was practically null, as in all soil layers investigated it showed determination coefficients (R2) smaller than 0.03 and not significant. The geostatistic analysis showed moderate structure of spatial dependency for PR in the layers of 0.05-0.10 and 0.10-0.15 m, and strong for yield; however, the conjugate spatial analysis of such attributes showed no correlation, therefore, the spatial variability of PR did not influence the yield.