Exploring the spatial relations between soil physical properties and apparent electrical conductivity

Relations between the apparent electrical conductivity of the soil (ECa) and top- and sub-soil physical properties were examined for two arable fields in southern England (Crowmarsh Battle Farms and the Yattendon Estate). The spatial variation of ECa and the soil properties was explored geostatistically. The variogram ranges showed that ECa varied on a similar spatial scale to many of the soil physical properties in both fields. Several features in the map of kriged predictions of ECa were also evident in maps of the soil properties. In addition, the correlation coefficients showed a strong relation between ECa and several soil properties. A moving correlation analysis enabled differences in the relations between ECa and the soil properties to be examined within the fields. The results indicated that relations were inconsistent; they were stronger in some areas than others. A regression of ECa on the principal component scores of the leading components for both fields showed that the first two components accounted for a large proportion of the variance in ECa, whereas the others accounted for little or none. For Crowmarsh topsoil sand and clay, loss on ignition and volumetric water measured in the autumn had large correlations on the first component, and for Yattendon they were large for topsoil sand and clay, and autumn and spring volumetric water. The cross-variograms suggested strong coregionalization between ECa and several soil physical properties; in particular subsoil sand and silt at Crowmarsh, and subsoil sand and clay at Yattendon. The structural correlations from the linear model of coregionalization confirmed the strength of the relations between ECa and the subsoil properties. Nevertheless, no one property was consistently important for both fields. Although a map of ECa can indicate the general patterns of spatial variation in the soil, it is not a substitute for information on soil properties obtained by sampling and analysing the soil. Nevertheless, it could be used to guide further sampling. (c) 2005 Elsevier B.V. All rights reserved.

Effect of manure application on crop yield and soil chemical properties in a long-term field trial of semi-arid Kenya

The sustainability of cereal/legume intercropping was assessed by monitoring trends in grain yield, soil organic C (SOC) and soil extractable P (Olsen method) measured over 13 years at a long-term field trial on a P-deficient soil in semi-arid Kenya. Goat manure was applied annually for 13 years at 0, 5 and 10 t ha(-1) and trends in grain yield were not identifiable because of season-to-season variations. SOC and Olsen P increased for the first seven years of manure application and then remained constant. The residual effect of manure applied for four years only lasted another seven to eight years when assessed by yield, SOC and Olsen P. Mineral fertilizers provided the same annual rates of N and P as in 5 t ha(-1) manure and initially ,gave the same yield as manure, declining after nine years to about 80%. Therefore, manure applications could be made intermittently and nutrient requirements topped-up with fertilizers. Grain yields for sorghum with continuous manure were described well by correlations with rainfall and manure input only, if data were excluded for seasons with over 500 mm rainfall. A comprehensive simulation model should correctly describe crop losses caused by excess water.

Modeling plant transpiration under limited soil water: comparison of different plant and soil hydraulic parameterizations and preliminary implications for their use in land surface models

Accurate estimates of how soil water stress affects plant transpiration are crucial for reliable land surface model (LSM) predictions. Current LSMs generally use a water stress factor, β, dependent on soil moisture content, θ, that ranges linearly between β = 1 for unstressed vegetation and β = 0 when wilting point is reached. This paper explores the feasibility of replacing the current approach with equations that use soil water potential as their independent variable, or with a set of equations that involve hydraulic and chemical signaling, thereby ensuring feedbacks between the entire soil–root–xylem–leaf system. A comparison with the original linear θ-based water stress parameterization, and with its improved curvi-linear version, was conducted. Assessment of model suitability was focused on their ability to simulate the correct (as derived from experimental data) curve shape of relative transpiration versus fraction of transpirable soil water. We used model sensitivity analyses under progressive soil drying conditions, employing two commonly used approaches to calculate water retention and hydraulic conductivity curves. Furthermore, for each of these hydraulic parameterizations we used two different parameter sets, for 3 soil texture types; a total of 12 soil hydraulic permutations. Results showed that the resulting transpiration reduction functions (TRFs) varied considerably among the models. The fact that soil hydraulic conductivity played a major role in the model that involved hydraulic and chemical signaling led to unrealistic values of β, and hence TRF, for many soil hydraulic parameter sets. However, this model is much better equipped to simulate the behavior of different plant species. Based on these findings, we only recommend implementation of this approach into LSMs if great care with choice of soil hydraulic parameters is taken

Impact of successive sugarcane harvests and trash management practices on soil microbiological properties

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)

Spatial variability of soil physical properties in two management systems in sugarcane crop

O objetivo deste trabalho foi caracterizar a variabilidade espacial da densidade do solo (Ds), teor de água no solo (θ) e porosidade total (Pt) em dois sistemas de manejo da colheita da cana-de-açúcar, com queima e sem queima, em um Latossolo Vermelho, na camada de 0-0,20 m. A área de estudo está localizada no município de Rio Brilhante-MS, na Usina Eldorado. A parcela de cada talhão apresentou malha com comprimento de 180 m e largura de 145,6 m, perfazendo 90 pontos distribuídos na forma de uma grade de nove colunas por dez linhas, com pontos distanciados 20 m de seu vizinho. Foram coletadas amostras de solo na camada de 0-0,20 m, nos anos agrícolas de 2007/2008 e 2008/2009. O sistema de colheita com queima apresentou maior densidade em relação ao mecanizado, nos dois períodos de análise. O teor de água no solo, assim como a porosidade, teve aumento proporcional com relação à diminuição da densidade do sistema de colheita com queima para com o mecanizado.

Influence of organic-mineral fertilization of an oxisol on soil chemical properties and Bracharia brizantha production

A utilização de fertilizante organomineral da indústria produtora dos aminoácidos lisina e treonina pode melhorar a fertilidade de solos tropicais. O presente trabalho teve como objetivo avaliar a influência de diferentes dosagens do fertilizante organomineral denominado Ajifer L-14 nos atributos químicos e no aumento de produção de forragem de um Latossolo Vermelho do noroeste paulista. O delineamento utilizado foi em blocos casualizados, com sete tratamentos e quatro repetições. Os tratamentos foram: T1- testemunha (sem aplicação de Ajifer L-14); T2- testemunha com vegetação natural; T3- adubação mineral de acordo com a necessidade da cultura e a análise do solo (usando 1,35 kg de ureia, 2,20 kg de superfosfato simples e 0,51 kg de KCl por parcela, o que corresponde a 60 kg de N, 40 kg de P2O5 e 30 kg ha-1 de K2O, respectivamente); T4- adubação com Ajifer L-14 de acordo com a recomendação da análise química do solo (40 L parcela-1, o que corresponde a 60 kg ha-1 N); T5- adubação com Ajifer L-14 em dosagem 50 % acima da recomendação (60 L parcela-1, o que corresponde a 90 kg ha-1 N; T6- adubação com Ajifer L-14 em dosagem 50 % abaixo da recomendação (20 L parcela-1, o que corresponde a 30 kg ha-1 N); T7- adubação com Ajifer L-14 em dosagem 25 % acima da recomendação (50 L parcela-1, o que corresponde a 75 kg ha-1 N); e T8- adubação com Ajifer L-14 em dosagem 25 % abaixo da recomendação (30 L parcela-1, o que corresponde a 45 kg ha-1 N). Nas profundidades de 0,0-0,1 e 0,1-0,2 m, avaliaram-se os seguintes atributos químicos do solo:, teor de matéria orgânica (MO), pH, K+, Ca2+, Mg2+, capacidade de troca catiônica (CTC), acidez potencial e saturação por bases. A aplicação do fertilizante organomineral não influenciou os atributos químicos do solo. Na análise de regressão, houve relação polinomial entre as doses de aplicação do fertilizante organomineral e a produção de massa seca e proteína bruta de Bracharia brizantha.

Recovery of soil physical properties by green manure, liming, gypsum and pasture and spontaneous native species

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

Recovery of soil microbiological properties in a degraded area planted with Corymbia citriodora and Leucaena leucocephala

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

Prediction and spatial variability of soil dynamic properties in sugar cane fields of São Paulo State Brazil

The objective of this work was to model and diagnose the spatial variability of soil load support capacity (SLSC) in sugar cane crop fields, as well as to evaluate the management impact on São Paulo State soil structure. The investigated variables were: pressure preconsolidation (sigma(p)), apparent cohesion () and internal friction angle (). The conclusions from the results were that the models and spatial dependence maps constitute important tools in the prediction and location of the mechanical internal strength of soils cultivated with sugar cane. They will help future soil management decisions so that soil structure sustainability will not be compromised.

Doses and sources of nitrogen fertilizer and their effects on soil chemical properties and forage yield of Brachiaria brizantha cv. Xaraes

Forage plants, particularly the Brachiaria genus, are the main source of nutrients for cattle and are at times the only feed offered. The concentration of elements in the plant is related to the soil, fertilization, climate, season, variety, and cultural practices. An experiment on dystrophic Red-Yellow Latosol soil in Aracatuba, São Paulo was performed to evaluate the effects of the doses and sources of nitrogen fertilizers on the chemical properties of the soil and the dry matter yield of the grass Brachiaria brizantha cv. Xaraes. A randomized block design was employed involving three replicates in a 3 x 3 factorial, with three doses (100, 200 and 400 kg ha(-1) year(-1)) and three sources (Ajifer (R) L40, ammonium sulfate and urea) of nitrogen and a control treatment without nitrogen (zero). The greatest effects on the chemical properties of the soil as a function of nitrogen fertilization in the Xaraes grass were observed in the topsoil. The use of Ajifer (R) L40 and ammonium sulfate as sources of nitrogen had similar effects, with an increase in the sulfur content and a reduction in the soil pH at the superficial layer. The use of the fertilizers Ajifer (R) L40, ammonium sulfate and urea did not affect the micronutrient contents, except for Fe and Mn, and did not alter the sodium concentration or electrical conductivity of the soil. The dry matter yield of Xaraes grass was similar for all three nitrogen sources.

Specific depth cone resistivity measurements to determine soil engineering properties

The University of British Columbia (UBC) began performing piezocone penetration tests (CPTU) with electrical resistivity measurements (RCPTU) in 1989. Since then, RCPTU research at UBC has focused on obtaining geo-environmental parameters such as fluid resistivity and soil engineering properties such as porosity and degree of saturation from measurements of bulk soil electrical resistivity using the empirical relationship proposed by Archie (1942). Within this framework, the paper illustrates and discusses important design and calibration issues for resistivity modules such as the use of isolated circuitry to achieve linear calibrations over large ranges of resistivity. The suitability of RCPTU measurements for determination of geo-environmental and geotechnical parameters are assessed using typical ranges of soil and groundwater properties and methods of isolating individual factors for study are discussed. Illustrative examples of RCPTU research efforts including the environmental characterization of mine tailings, delineation of saline water intrusions in fresh water aquifers and the quality control of geotechnical ground densification are presented throughout the text. It is shown that groundwater temperature and hence ion mobility is not significantly altered by frictional heat generated during piezocone penetration and that ratio-based approaches to monitoring soil porosity can be used to eliminate the requirement for extensive groundwater sampling programs. Lastly, it is shown that RCPTU measurements above the water table can only be made using resistivity modules that are stable over a large range of resistivities and that such measurements are the most difficult to interpret because of grain surface conduction effects and generally unknown fluid resistivities.

Soil microbial properties after 5 years of consecutive amendment with composted tannery sludge

Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)