The quantification of soil structure by image analysis

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Evaluation of methods for inferring air and water properties of soils from field morphology

The accurate characterization of soil water and air properties is difficult in soil survey because of logistic constraints. Less reliable surrogates are commonly used to estimatethese properties. The surrogates provide a method for moving from measures that tendto be static and semi-empirical to those characterizing soil processes. The utility of fourschemes for predicting air-filled porosity, available water capacity and saturated hydraulicconductivity on the basis of field-determined soil morphology has been assessed using datafrom a limited number of profiles with features commonly encountered in Australia. Noneof the systems provided statistically significant predictions of available water capacity andthe results for air-filled porosity were moderate (McKeagueet al.(1986), r2=0-58; Halletal.(1977), r2=0-64; Williams efal.(1991), r2=0-70). Encouragingly, the Hollis and Woods (1989) system generated good predictions of field-saturated hydraulic conductivity (r2= 0.77). It is concluded that better measurement methods and programs of data collection are needed for both the properties used as surrogates (e.g.morphology) and those for which predictions are required (e.g. air and water properties)

Four Pillars of digital land resource mapping to address information and capacity shortages in developing countries

Like many developing countries, the Philippines has a shortage of land resource information at sufficiently fine scales for effective land-use planning. The country is also short of capacity to acquire such information with a declining number of soil surveyors and limited capability and resourcing of soil analytical laboratories. Digital land resource mapping (DLRM) provides an opportunity to address these shortages. A project in the Cabulig watershed (220km2) of Northern Mindanao developed operational protocols by combining existing technologies to form a DLRM framework based on four 'pillars'.1)Statistically-based sampling strategy to ensure unbiased coverage of the range of landscape positions, and remove the need for expert judgement in sample site selection in the field.2)Simplified site protocols that concentrate on soil specimen collection rather than soil description and classification.3)Rapid soil analysis by mid-infrared (MIR) to estimate soil attributes for all layers at every site after developing local calibrations using conventional laboratory analysis.4)Statistical spatial prediction to map a range of soil attributes using piece-wise linear regression modelling with bootstrap aggregation. Overall, this framework can enable more efficient use of scarce pedological expertise and laboratory facilities by devolving many tasks to local, non-expert teams. An added benefit is that the local teams acquire soil literacy and can help with on-going interpretation and application of the survey results. We also discuss how we addressed some of the practical issues that arise with conducting soil survey in the context of a developing country and in a remote survey area with rugged terrain

Tráfego de máquinas agrícolas e alterações de bioporos em área sob pomar de laranja Agricultural machinery traffic and alterations in biopores under an orange orchard

O estudo micromorfológico permite observar detalhadamente todas as modificações causadas na estrutura e no espaço poroso do solo, impostas pelo cultivo e pelo tráfego de máquinas agrícolas. Este trabalho testou a hipótese de que a compactação causada pelo tráfego de máquinas influi, diferencialmente, na forma e na distribuição das classes de poros, os quais podem ser utilizados como indicadores da qualidade do solo. O objetivo deste trabalho foi avaliar e quantificar, por meio de estudos micromorfológicos, as modificações na porosidade oriunda da atividade biológica (bioporos) em um Latossolo Vermelho-Amarelo sob pomar de laranja submetido ao tráfego de máquinas. Amostras indeformadas foram coletadas na superfície (0-12 cm) de uma área sob pomar de laranja, abrangendo as posições: entrerodado (ER), rodado (R) e projeção da copa (PC), utilizado, como testemunha, um perfil sob mata. Os resultados mostraram que o aumento na diversidade de poros está diretamente relacionado com os processos de degradação da estrutura do solo e que o estudo da ocorrência das classes de poros mostrou-se mais eficiente na identificação da compactação do solo em estádios iniciais que os dados de densidade do solo.<br>Soil micromorphological studies enable a detailed observation of the modifications in soil pore structure and space imposed by cultivation and agricultural machinery traffic. This study tested the hypothesis that compaction caused by machinery affects the form and class distribution of pores in a distinct way and that such alterations can be used as soil quality indicators. The objectives of this study were to evaluate and quantify, through micromorphological studies, the modifications in porosity caused by biological activity (biopores) in a Red-Yellow Latosol (Oxisol) under an orange orchard subjected to machinery traffic. Undisturbed samples were collected from the surface soil layer (0-12 cm) in the following positions: in-between wheel tracks (ER), wheel tracks (R) and plant canopy projection (PC). For comparison purposes, samples were also collected from a soil profile under natural vegetation. Results showed that the increase in pore diversity is directly related to the process of soil structure degradation. The study of pore classes was more effective to identify soil compaction in its initial state than soil density data

Hydro-physical characterization of soils under tropical semi-deciduous forest

The study of the hydro-physical behavior in soils using toposequences is of great importance for better understanding the soil, water and vegetation relationships. This study aims to assess the hydro-physical and morphological characterization of soil from a toposequence in Galia, state of São Paulo, Brazil). The plot covers an area of 10.24 ha (320 × 320 m), located in a semi-deciduous seasonal forest. Based on ultra-detailed soil and topographic maps of the area, a representative transect from the soil in the plot was chosen. Five profiles were opened for the morphological description of the soil horizons, and hydro-physical and micromorphological analyses were performed to characterize the soil. Arenic Haplustult, Arenic Haplustalf and Aquertic Haplustalf were the soil types observed in the plot. The superficial horizons had lower density and greater hydraulic conductivity, porosity and water retention in lower tensions than the deeper horizons. In the sub-superficial horizons, greater water retention at higher tensions and lower hydraulic conductivity were observed, due to structure type and greater clay content. The differences observed in the water retention curves between the sandy E and the clay B horizons were mainly due to the size distribution, shape and type of soil pores