Conversion of Munsell color coordinates to Cie-L*a*b* system: Tables and calculation examples

The widely used Munsell optical system is unsuitable for the statistical treatment of data for assessing the role of pigments in soil color. The CIE-L*a*b* system is more efficient for this purpose. This article contains a table for converting data on soil color from one scale to the other based on the example of oxisols (Brazil) and pale (Yakutia) and alluvial (Spain) soils. The advantages of the CIE-L*a*b* system for characterizing soil color have been shown.     

Using soil survey information to characterize the soil-water state*

Uses of soil for a wide variety of purposes are largely governed by interactions between soils and climatic conditions. The soil-water state at any given moment depends on the hydraulic properties of the soil horizons, the weather and soil drainage. Emphasis in this presentation is on the manner in which the soil-water state is being characterized in the context of land evaluation. Land evaluation is concerned with the assessment of land performance when used for specified purposes (FAO, 1976). Current and future developments in land evaluation are discussed, emphasizing the particular input of soil survey when using computer simulation models for the soil-water regime. The soil-water regime plays a key role in land evaluation, as it governs the soil-water state at any given time during the year.     

土壤制图中土壤类型配色模型构建与应用

在全国1∶5万土壤图集制图中,土壤类型的配色既需表现土类等高级类型的分布特征,也要表现土属等较低级类型的差别。我国土壤低级类型众多,且1∶5万基本比例尺图幅达2万余幅,采用传统人工设色方法进行土壤制图,不仅效率低,而且难以保持图幅间土壤颜色的协调一致性。针对这一技术难题,本研究采用图幅间相似配色方法和人机交互的设计思想,通过建立1个多层级管理色库、人工设置土壤类型的Q配色单元及其多个近似色系(色组),建立了Q配色单元的避让选色和区域土壤特征分析等5个组件模型,构建了土壤类型配色模型(SCO-Model)。该模型在大比例尺土壤制图中不仅反映了区域土壤的总体分布特征,也表达了土壤类型间的差异,特别是实现了大比例尺土壤制图中土壤类型的快速智能配色,大大提高了制图效率。     

A DGGE-cloning method to characterize arbuscular mycorrhizal community structure in soil

Although arbuscular mycorrhizal fungi (AMF) are crucial for ecosystem functioning, characterizing AMF community structure in soil is challenging. In this study, nested polymerase chain reaction (PCR) and denaturing gradient gel electrophoresis (DGGE) were combined with cloning of fungal 18S ribosomal gene fragments for the rapid comparison of AMF community structure in soil. Reference AMF isolates, representing four major genera of AMF, were used to develop the method. Sequential amplification of 18S rDNA fragments by nested PCR using primer pairs AM1-NS31 and Glo1-NS31GC followed by DGGE analysis yielded a high-resolution band profile. In parallel, 18S rDNA fragment clone libraries were constructed and clones screened by DGGE. Sequence identity was inferred by matching the electrophoretic mobility of the sample fingerprint bands to that of bands from individual clones. The effectiveness of this approach was tested on soil samples from different ecosystems, yielding reproducible, complex DGGE band patterns specific to each site. The coupling of PCR–DGGE with clone library analysis provides a robust, reliable, and precise means to characterize AMF community structure in soils.     

Aggregation indices to characterize structural breakdown of dry soil samples by air slaking

The objectives of this study were to develop a simple test to assess air slaking effects on structural breakdown of dry soils and with the help of the test, to verify whether observations made by Gath (1995) on artificial soil samples are also valid for undisturbed soil samples. The proposed slaking test and the derived aggregation indices allow for an indirect assessment of the effect of air slaking. It is possible to use the test as a means of grouping soil structure with respect to slaking susceptibility. Thus, soil samples with clay contents < 10% and granular or weakly coherent structure are practically completely dispersed upon immersion. Soils with > 30% clay are well aggregated in angular blocks and prisms, and slaking will stop at a microaggregate level. Loess soils, which usually have a range of 10 to 30% clay content and coherent to subangular blocky structure show an intermediate behaviour. Finally, the results obtained here using undisturbed soil samples are in line with those obtained by Gäth (1995), indicating that at a given water content rate of water uptake as influenced by hydraulic conductivity, sample size and bulk density is a major factor controlling effects of air slaking. However, when comparing samples of different origin, increase in clay content is the principal factor that reduces slaking effects.     

Micromorphological analysis to characterize structure modifications of soil samples submitted to wetting and drying cycles

The physical characteristics of the soil surface are of extreme importance in relation to energy and matter transfer processes between the atmosphere and the soil. Soil internal structure changes can be due to natural or artificial causes and one important natural process is the alternation of wetting and drying (W–D) processes, which induce swelling and shrinking of soil particles, causing modifications in pore size and shape. To study the consequence of these W–D events on possible modifications in pore size distribution, pore number, and pore shape of soil samples collected in metal rings pore image analysis was used. Samples were taken from profiles of three soils of different characteristics, named as Geric Ferralsol (GF), Eutric Nitosol (EN), and Rhodic Ferralsol (RF). Confined volumetric samples (50 cm³) were submitted to none (T₀), three (T₁), and nine (T₂) subsequent W–D cycles. Image cross sections of resin impregnated soil permitted the micrometric and macrometric characterization of changes in soil structure induced by sequences of W–D cycles. Duncan's statistical test indicated that there were significant differences (α = 0.05) among treatments for all soil samples. General conclusions indicate that total pore area increased for all soils after repeated W–D processes, specifically 19.0 to 28.9% for GF, 5.9 to 11.7% for EN, and 13.0 to 17.2% for RF. Main changes of pore diameter occurred in pores larger than 500 μm, and minor changes were observed in the total number of these pores. It is demonstrated that soil samples undergo important changes in their structures after repeated W–D cycles. The information presented here is very important for the evaluation of soil water retention curves and other soil hydric properties, because soil samples used in these procedures are collected in rings and frequently submitted to several W–D cycles.     

Using time domain reflectometry to characterize cattle and pig slurry infiltration into soil

Abstract. The rate and extent to which cattle or pig slurry infiltrates into soil after application is one of the important factors determining the rate and extent of subsequent ammonia (NH₃) volatilization. Better characterization of the infiltration process is required to improve predictive models of NH₃ losses after land spreading. This paper describes a laboratory system using time domain reflectometry to measure slurry infiltration into soil columns. This system enabled semi-continuous, non-destructive infiltration measurements to be made, assessing the influence of slurry type, dry matter (DM) content, soil type and soil water tension. Differences were noted in the infiltration behaviour of cattle and pig slurries. For cattle slurry, DM content (range 1.7–7.1%) was the main influencing factor. Infiltration rate rapidly decreased with increasing DM content and there was no influence of soil type or water tension. For pig slurry, all of the slurry infiltrated into a sandy clay loam soil within the first hour, regardless of DM content (range 1.5–4.7%), whereas only 60% infiltrated into a clay loam soil over the same time period (slurry DM content 2.1%).     

Use of the fluorescent antibody technique to characterize equilibrium survival concentrations of Bradyrhizobium japonicum strains in soil

Summary The ability of Bradyrhizobium strains to survive saprophytically in soil was studied by means of fluorescent antibodies (FA). It was found that the recovery rate may be considered a constant value although the limit of detection by the FA technique is approximately 10³ bacteria g^–1 soil. By studying the survival kinetics of B. japonicum strains introduced into soils, we observed that whichever soil-strain combination was tested in a given soil during the incubation all the different populations of a strain reached the same survival balance level, generally about 10³–10⁴ Bradyrhizobium g^–1 soil. When we reintroduced strains into a soil containing rhizobia of the same specificity, the new inhabitants reached the same equilibrium level as that of the initial population. The balance threshold level does not appear to be a very sensitive way to classify, strains on their saprophytic ability. We suggest that survival kinetics should be characterized by the rate at which the population reaches equilibrium.     

土壤墒情自动测报系统在绿洲农业区的应用

目前对采用水文干旱方法,即通过监视农田墒情的变化来建立抗旱决策信息系统研究还很少,文章阐述在干旱灌区建立土壤墒情监测预报和灌溉决策信息系统的重要性,提出适用于干旱灌区的土壤墒情监测方法和作物灌水预报模型,对土壤墒情自动测报及灌溉决策系统的信息传输、结构及功能作了详细论述。研究表明,通过计算机信息技术对农田墒情、气象信息、灌溉用水以及农业生产等综合信息实行一体化系统管理,提高了灌溉管理水平,节约了水资源。研究成果在干旱、半干旱地区具有参考和应用价值。     

Chemical fractionation to characterize changes in sulphur and carbon in soil caused by management

Classical chemical fractionation of soil sulphur (S) into HI‐reducible S and carbon‐bonded S does not separate S in soil into fractions that have differing mineralization potentials. Other techniques are needed to separate organic S into more labile and less labile fractions of biological significance, irrespective of their bonding relations. We have sequentially fractionated soil S and carbon (C) into their ionic forms released onto ion‐exchange resins and organic S and C extracted in alkali of increasing concentration. We evaluated the technique on pasture and arable soils that had received various fertilizer and cultivation treatments. Total S and C were greater in the soil of the fertilized pasture than in that of the unfertilized pastures. Continuous arable cropping decreased total soil S and C, whereas restoration to pasture caused an accumulation. Resin, 0.1 m NaOH, 1 m NaOH and residual fractions accounted for between 1–13%, 49–69%, 4–16% and 19–38% of total soil S and between 5–6%, 38–48%, 5–7% and 46–53% of total soil C, respectively. Among different S and C fractions, the size of the 0.1 m NaOH and residual fractions changed more with the change in land use and management. The 0.1 m NaOH fraction had a narrower C:S ratio (50–75:1) than did the residual fraction (96–141:1). The significant degree of change in these two fractions, caused by differences in land management, indicates that they may be useful indicators of change in ‘soil quality’.     

基于多源数据的盐碱地精确农作管理分区研究

为了便于对盐碱地实施变量管理和精确农作，以海涂围垦区盐碱土为研究对象，以NDVI数据、盐分数据以及作物产量数据作为分区变量，对一面积为15 hm²的盐碱地农田进行了基于多个数据源的精确农作管理分区研究。利用模糊c均值聚类方法进行分类分区，引入了模糊聚类指数(FPI)和归一化分类熵(NCE)作为最佳分区数目的判断标准，通过单项方差分析对分区结果进行比较和评价。研究发现，对本研究区，最佳的分区数目为三个。不同管理分区之间土壤化学性质(EC1:5,有机质，速效磷，速效钾，全氮，碱解氮以及阳离子交换量)的均值都存在着统计意义上的显著差异性，其中子区3具有最高的肥力水平和作物生产能力而子区1最低。利用所选取的三个变量，模糊c均值聚类算法可以较好地进行精确农作管理分区划分。分区结果不但可以指导采样, 而且可以作为变量管理的决策单元用于田间变量管理作业中,为精确农业变量投入的实施提供有效手段和决策依据。     

Rapid,objective measurement of soil color with a tristimulus colorimeter

Abstract

The color of 100 soil sanples collected in Florida and Brazil was measured conventionally with Munsell color charts and with a tristimulus colorimeter (Minolta Chroma Meter 200) progranmed to record reflected color in Munsell notation. The instrument‐derived color readings were highly reproducible and more precise than the visual determinations. It appears that the Chroma Meter 200, an instrument usually used for fruit and juice color measurenent, can be used to get objective soil color measurenents, free of individual color perception differences, and with better interpolated values.     

Quantitative evaluation of the microbial nutrient sink in soil in relation to a model system for soil fungistasis

A quantitative approach was devised to evaluate the influence of soil microbial activity as a sink for nutrients exuded by fungal spores as a factor in soil fungistasis. The approach was based on measuring the CO₂ evolved from microbial respiration of ¹⁴C-labelled exudates from conidia of Cochliobolus victoriae incubated on soil. The amount of exudate lost by spores on soil was greater than the amount lost by spores incubated on a bed of sand undergoing leaching at a flow rate of 110 ml h^?1. where restriction of germination was similar to that on soil. Increasing flow rates in the leaching system increased spore exudation and reduced germination. Germination of C. victoriae conidia on membrane filters floated on distilled water decreased as the volume of water increased. The results indicate that the microbial nutrient sink of soil is sufficient to impose soil fungistasis.     

Evaluation of a method to characterize the phenolic profile of organic and conventional tomatoes

The present study aims to compare the phenolic profiles of organic and conventional tomatoes bought in the market. For the quantification and identification of individual polyphenols, liquid chromatography coupled to mass spectrometry in tandem mode (LC-MS/MS) was carried out. Confirmation of the compounds previously identified on the triple-quadrupole was accomplished by injection in the high-resolution system (QToF-MS). In this way, 34 compounds were identified in tomato fruits. Recoveries of targeted polyphenols exceed 78% for conventional and organic tomatoes, respectively. The method intraday precision ranged between 3 and 5%, whereas the interday one was below 12%. Comparing the analyses of tomatoes from conventional and organic production systems demonstrated statistically higher levels (P < 0.05) of phenolic compounds in organic tomatoes. This methodology allowed finding differences in the bioactive components of organic and conventional tomatoes not previously reported.     

Application of a low-cost database to soil erosion and soil conservation studies in the Awash Basin,Ethiopia

In large-scale land resource planning exercises, Geographical Information Systems (GIS) form a valuable means of storing, retrieving, displaying, and analysing spatially-referenced data, as well as enabling the simulation of the consequences of various alternative development options. However, at this scale only generalized policies for the allocation of finance can be made, and the implementation of those policies will invariably require detailed evaluation at the local level. This suggests that expenditure on the central planning process itself should be limited, with funds reserved for later site studies. The form of GIS adopted centrally should also lend itself to easy use and interpretation by policymakers and planners. These requirements suggest that GIS development using proprietary off-the-shelf database management software may be preferable to high-technology GIS software. This paper outlines the development of such a GIS, based on dBase-III-plus and its internal programming language, in the analysis of problems of soil erosion and soil conservation in the large (110,000 km²) drainage basin of the Awash River in Ethiopia. The methodology employed involves the FAO modification of the Universal Soil Loss Equation, which clearly lacks a secure process basis, but is appropriate for the scale of planning involved and the quality of calibration data available. The GIS is used to map patterns of soil erosion, to identify target areas for conservation on the basis of criteria of sensitivity to land use change, and to assess the costs and benefits of conservation work in those areas. It is suggested that the simple form of GIS involved in this study has much to offer environmental managers in developing countries in the rapid development of plans for soil conservation.     

彩色红外遥感航片在滑坡调查中的应用

晋西三川河流域黄土区的滑坡,可根据“滑床”、“稳定性”和“滑坡体体积”三个指标分类、命名。调查滑坡可以1:100,000MSS彩色合成卫片,1:50,000和1:100,000地形图以及地质、地貌、水系、植被和土壤侵蚀等图件作为主要信息源。然后,通过日视判读从彩色红外遥感航片上确定滑坡分布、滑坡类型、滑坡稳定性和滑坡的规模等。分析结果说明,滑坡作的面积与其长度、宽度之间有很高的相关性,用DBASEⅢ数据库管理系统支配,把网格化的滑坡类型分布图的有关数据输入计算机,可计算出滑坡个数、面积和滑塌量,得到滑坡分布密度等10幅专题图件,为该流域的整治与开发提供滑坡方面的信息。     

Contribution of red alder to soil nitrogen input in a silvopastoral system

Studies on Alnus rubra Bong. (red alder) were carried out to assess its potential for use as a component of a silvopastoral system. Comparison was between two treatments: red alder at 400 stems ha⁻¹ (silvopasture) and red alder at 2,500 stems ha⁻¹ (forestry control). δ¹⁵N values close to zero were recorded in all red alder plant parts except for root nodules, indicating that a large proportion of N in red alder was fixed from the atmosphere. Overall, it was estimated that there was 63.45 kg N ha⁻¹ fixed N accumulated in red alder trees, and the rate of N fixation was estimated at 30.95 kg ha⁻¹ year⁻¹ in the silvopasture treatment. The total amount of N that could potentially be added to the soil in the silvopasture treatment as a result of decomposition of senescent leaves, roots, and dead nodules was estimated at 40.56 kg ha⁻¹ year⁻¹. Of the total N added to the soil, 27.1 kg ha⁻¹ year⁻¹ was due to N fixation from the atmosphere. These results show that red alder has a potential to improve and maintain soil fertility in a silvopastoral system.     

Correlation of lycopene measured by HPLC with the L, a, b color readings of a hydroponic tomato and the relationship of maturity with color and lycopene content

Tomatoes (Lycopersicon esculentum cv. Laura) were separated, according to the ripening stage, by a sensory panel into seven groups, and color was measured on the tomato surface with a Minolta Chroma meter. The L, a, b, hue, chroma, and lycopene content were plotted against the maturity stages of the tomatoes, and several good correlations were found. The a/b ratio and the lycopene content were the parameters that allowed six of seven maturity groups in the tomato to be statistically distinguished. The lycopene content, measured by HPLC, was also correlated with the color measurements, and the a, a/b, and (a/b)(2) color factors produced the best regressions. An estimation of the lycopene content in tomatoes can be achieved by using a portable chroma meter, with a possible field usage application. Equations to calculate the lycopene content of tomatoes based on the color readings are reported.     

Application of a soil core method to investigate the effect of oxygen concentration on denitrification

The effect of O₂ concentration on denitrification rate was investigated in sandy loam and clay loam soils. Oxygen at different concentrations and acetylene were recirculated through freshly-collected soil cores. Denitrification rates under anaerobic conditions with argon as the recirculating gas were also determined. The effect of O₂ on denitrification rate among cores could then be normalized by expressing the data as percent of the anaerobic rate. Denitrification rates were less than 2% of the anaerobic rate for O₂ concentrations greater than 3%, but greatly increased at concentrations below 0.5% O₂. For individual cores the denitrification rate increased 2- and 4-fold as the O₂ content of the recirculating gas was decreased from 20 to 5%. The pattern of denitrification rate versus O₂ concentration was very similar to that generated from the theoretical model of K. A. Smith, which describes the proportional anaerobic volume of soil aggregates as a function of O₂ concentration. A soil gas sampling probe is described which uses porous Gortcx tubing buried in horizontal soil layers. The recirculating gas in the denitrificating assay 4system could then be adjusted to match the soil O₂ content measured at the time of sampling.