Soil Physical Quality Indicators Research Articles

Alterações na qualidade física de um latossolo amarelo sob pastagem

Indicadores de qualidade física do solo representam uma importante ferramenta no estudo das alterações que ocorrem no solo em função de ações de uso e manejo. Objetivou-se com este estudo utilizar o intervalo hídrico ótimo (IHO) e o índice-S (declividade da curva de retenção de água no solo no ponto de inflexão) para quantificar as alterações físicas do solo promovidas pelo sistema de pastagem, tendo como referência um solo sob mata. O estudo foi realizado em um Latossolo Amarelo distroférrico típico sob mata nativa e pastagem, onde foram coletadas amostras deformadas e indeformadas nas profundidades de 0-5 e 25-30 cm, utilizadas para determinação do carbono orgânico do solo e análises físicas. Os valores de índice-S, com exceção do solo sob mata (0-5 cm), estiveram abaixo do limite sugerido para separar solos com boa e pobre qualidade estrutural. O IHO foi fortemente reduzido no solo sob pastagem, chegando a atingir valor zero. O principal fator limitante para a disponibilidade de água foi a resistência à penetração, que exceto em mata (0-5 cm), atuou como limite inferior do IHO em todas as áreas e profundidades avaliadas. Os indicadores de qualidade física do solo, IHO e índice-S, apresentaram conformidade quanto à avaliação da qualidade física dos solos estudados e indicaram as alterações físicas promovidas no solo sob sistema de pastagem.

Soil physical quality of the Indo-Gangetic plains and black soil region.

Understanding the physical quality of soil that influences its hydraulic behaviour helps in formulating appropriate water management strategies for sustainable crop production. Saturated hydraulic conductivity ( K s ) is a key factor governing the hydraulic properties of soils. K s can be estimated through various techniques. In the present article we have developed and validated the regression models to predict K s of the soils of the Indo- Gangetic Plains (IGP) and the black soil regions (BSR) under different bioclimatic systems. While particle size distribution was found to be a key factor to predict K s of the BSR soils, organic carbon was found useful for the IGP soils. Moreover, the models for K s of both soils were strengthened by putting in CaCO 3 and exchangeable sodium percentage content. It seems there is ample scope to study the interaction process for revising K s to desired levels through management practices in these two important food-growing zones. An index of soil physical quality, derived from the inflection points of the soil moisture characteristic curves could well explain the impact of management practices on soil physical quality.

Soil evolution after land-reshaping in mountains areas (Aosta Valley, NW Italy)

Mountain agriculture needs to face several limitations related to climate and topography. Land levelling, reshaping, and terracing are widely adopted in Europe, in order to ease mechanization and make agriculture more profitable. However, while the economic and productive benefits of these operations are well known, the effects on soil chemical and physical properties are not always assessed, and need constant monitoring over time. Intense soil rebuilding has been carried out in Aosta Valley (NW Italian Alps) to improve the accessibility and mechanization, including irrigation, of mountain grasslands.In this research we considered 3 study sites established in grasslands subject to soil rebuilding practices. The aim was to investigate the effects of land-reshaping operations on soil chemical and physical properties, by comparing changes in some selected soil properties such as organic C and soil laboratory indexes for quantifying soil structural resistance.The soil profiles generally showed a simpler morphology after rebuilding. Soil structure and consistency, that are recognized as soil physical quality indicators, after a sharp negative effect of the disturbance (i.e. decrease in liquid limit, increased soil aggregates loss) generally showed a trend towards the restoration of the characteristics of the original soils in the medium or long-term time span. Despite the limited sample size, the results represent a first attempt to assess the effects of a technique which is being more and more applied in a mountain region, such as the Aosta Valley Region, where manufactured soils are a significant part of agricultural land. The main findings of our research indicated that: (1) structure and consistency of soils (i.e. aggregate loss, LL, PL) can be used as indicators of soil quality in response of anthropogenic soil disturbance due to land-reshaping operations, as they reflect the evolution of soil properties after intense disturbance; (2) after disturbance, soil recovery was relatively quick, despite the strong deterioration of the physical quality in the immediate (∼6–12 months) aftermath of the operations.

Temporal dynamics of the physical quality of an Andisol under a grazing system subjected to different pasture improvement strategies

The south of Chile presents adequate conditions for the development of pastoral ecosystems in volcanic soils. The improvement strategies of these pastures consider soil tillage and fertilization. Andisols have special physical properties, however, their ability to support high stress levels affecting the soil physical quality should be defined. The aim of this study was to evaluate the evolution of the effect of different pasture improvement strategies on the physical quality of an Andisol. The study was carried out in the Estación Experimental Agropecuaria Austral (39°46′ S, 73°13′ W), on a Duric Hapludand. Four treatments were randomly distributed corresponding to a mixed binary species (T1: Lolium perenne L.+Trifolium repens L.), a multiple species mixture (T2: Bromus valdivianus Phil., L. perenne, Dactylis glomerata L. and T. repens) both of which were tilled, and another two that had no mechanical intervention of the soil, which was degraded naturalized pasture without fertilization (T3) and, finally, one that represented a naturalized degraded pasture with fertilization (T4). Additionally, a naturalized, degraded pasture without intervention was analyzed, which corresponded to the initial situation (IS) of the pasture. Undisturbed samples were taken between 1 and 10cm in December 2010 and October 2011. The bearing capacity of the soil (BC), the water retention curve (WRC), the saturated hydraulic conductivity (Ks) and the air conductivity (kl) were determined. Soil physical quality indicators were derived such as plant available water (PAW), pore continuity indexes (C2 and C3) and the S index for physical quality. The tillage of the soil separated the pastures, grouping them into either disturbed (T1 and T2) or non-disturbed (T3 and T4). In general, parameters that were derived from the pore volume never reached the critical levels (e.g., PAW>20%, S Index>0.035) proposed in the literature. On the other hand, parameters that define the functionality of the porous system (kl), showed differences in one order of magnitude between pastures that maintained their structure (T3 and T4) compared to the tilled ones (T1 and T2), so that for T4 the pore continuity index (C2 and C3) increased by 300% and the volume of blocked pores (ϵb) did not reach 1%. At the same time, properties that define the performance of the pores evolved positively over time in a more intense manner in pastures that maintained their structure (T3 and T4). However, this does not mean that in the long term these pastures would not present conditions of physical degradation.

SAWCal: A user-friendly program for calculating soil available water quantities and physical quality indices

Conventional plant available water (PAW), least limiting water range (LLWR), integral water capacity (IWC) and integral energy (EI) are different approaches to quantify the soil water availability for plants. The PAW, the soil water between field capacity (FC) and permanent wilting point (PWP), is based merely on the soil matric potential. The LLWR in addition considers oxygen deficit and high soil penetration resistance limitations for plant growth excluding some of the restrictions of the PAW concept. The IWC approach adapts better with natural phenomena since it considers that the impacts of soil physical limitations on water uptake by plants are gradual and not in a cut-off form. Nevertheless, its calculation is laborious and time-consuming. The EI quantifies the energy required by plants to remove a unit amount of water from the soil over the available water range. As more attention is given to new soil available water (SAW) approaches nowadays, developing an algorithm and computer graphical user interface (GUI) for calculation of these indices (especially the IWC) would help to popularize the approaches’ application. Here we report the development of a software called SAWCal (Soil Available Water Calalculator) for calculating PAW, LLWR, IWC, and EI and related quantities. It also calculates the soil physical quality index (S), the slope of the water retention curve at its inflection point, proposed by Dexter (2004a,b,c). This software only needs the parameters of soil water retention and soil penetration resistance models. The C#, being an evolution of C++, as an object-oriented programming (OOP) was employed to develop the program. The parameters of single-porosity van Genuchten (1980) and dual-porosity Durner (1994) models are used to characterize the water retention and hydraulic conductivity functions for the soils with uni- and bi-modal pore size distributions, respectively. For establishing a continuous function of soil penetration resistance vs. matric suction, SAWCal uses a modified van Genuchten (1980) model or a power model depending on the user’s choice. When needed, the integration is performed numerically. SAWCal is a help-assisted user-friendly GUI to guide the user step-by-step through the procedures. It is also possible to export the program outputs in ASCII format compatible with MS Office and text-editing programs. The software is provided as a free supplementary material to this paper.

Land Use Impact on Soil Physical Quality and Soil Structure in Three Highland Watersheds of Ethiopia

Continuous monitoring of soil physical quality is essential in determining sustainability of land use in natural and managed ecosystems particularly; mountainous systems such as the Ethiopian highlands, where soil deterioration and degradation can become major threats to ecosystem and productivity. This study focused on assessment of soil physical quality (SPQ) by comparing values of soil indicator properties to their corresponding ‘ideal ranges’ established in literature and determining soil structural stability and aggregate associated carbon as influenced by land use types. It further employs factor analysis to identify appropriate SPQ indicators and soil structural indices that are dominantly influenced by each land use type in the three watersheds (namely; Jeldu, Diga and Fogera) of the Ethiopian highlands. Surface soil samples were collected from four adjacent agricultural land use types (namely; Grass fallow, Tree fallow, Homestead and Continuous field cropping) within each of the three watersheds for study of Dexter “S” index, aggregate associated carbon and aggregate stability and other SPQ indicators. Results revealed that soils were only adequate in Relative Field Capacity and Plant Available Water Capacity in all watersheds. The soils of the watersheds still maintained good physical quality but there are strong indications of low soil structural resilience and tendency to degrade. Factor analysis grouped SPQ indicators and structural indices into three factors: (Factor 1) structural stability (with soil organic carbon, aggregate associated organic carbon and aggregate size being the most dominant soil quality indicators); no dominant attribute for Factor 2 and Factor 3 is mainly soil texture (with clay being the most dominant). Soil improvement programme in the watersheds lies in management practices that will promote proper management of organic carbon as it is the principal SPQ indicator that influenced variation in other soil attributes.

Temporal changes of soil physical quality under two residue management systems

AbstractAlthough crop residue management is known to affect near‐surface soil physical quality, little is known about the temporal variability of these indicators over short time intervals. This study evaluates the temporal changes of nine indicators of soil physical quality. These are organic carbon content, structural stability index, bulk density, macroporosity, air capacity, relative field capacity, plant available water capacity, Dexter's S‐index and saturated hydraulic conductivity. A second set of soil physical indicators, based on the distribution of soil pore volume, was also evaluated. The indicators were determined in three different times during the growing cycle of winter durum wheat cultivated within a long‐term field research carrying out in Southern Italy and comparing two types of crop residue management, that is, burning (B) and soil incorporation (I). Only the bulk density changed over time for both treatments, although the air capacity also changed for the incorporation of wheat residues. Residual effects of the autumnal soil tillage and soil compaction were a common source of variability, irrespective of which treatment was used. Based on the existing guidelines for evaluating the physical quality of these agricultural soils, optimal or near‐optimal values were detected in about half of the cases under consideration. This suggests that both B and I create sufficiently good conditions for crop growth during the crop cycle. The comparison between observed and optimal soil pore distribution function was always poor. The pore volume distributions showed lower densities of small pores and relatively higher densities of large pores than the proposed optimal distribution. This study also suggests that the considered optimal or references curves probably cannot be applied successfully to a wide range of agricultural soils.

Long-term tillage, water and nutrient management in rice–wheat cropping system: Assessment and response of soil quality

Highly productive rice (Oryza sativa L.) and wheat (Triticum aestivum L.) systems are crucial for millions of rural and urban poor in the Indo-Gangetic Plains (IGP) of south Asia. Our objectives were to identify important biological, chemical and physical indicators of soil quality and incorporate them into a unified soil quality index (SQI) that could be used to help select best management practices for important cropping systems. Two tillage, three water management and nine nutrient management treatments were evaluated. Principal component analysis (PCA) was used to identify critical indicators and their relative weighting for a soil quality index (SQI) that was developed using the Soil Management Assessment Framework (SMAF). Two primary goals – productivity (PCASQI-P) and environmental protection (PCSQI-EP) were established. For the productivity goal, seven indicators were evaluated for their contribution to nutrient cycling, two for physical stability and support, and three for water relations. The environmental quality goal used the same functions and indicators plus three additional indicators affecting filtering and buffering, and one reflecting biodiversity and habitat. The hypothesis of the study was that the set of sensitive indicators would vary under contrasting tillage, nutrient and water management which could be encompassed to develop unified soil quality indices for assessing management induced changes in rice–wheat cropping system. The results confirmed that management goal strongly influenced indicator selection and that variations in those indicators can provide early warning against deterioration of soil quality. Puddling and irrigating rice after three days of drainage and using no tillage and two irrigations for wheat emerged as promising management for improved soil quality. Applying 25% of the recommended fertilizer N dose using farm-yard manure (FYM) for rice and domestic sewage sludge for wheat also improved soil quality. We conclude that the procedure used for indexing soil quality in this study could not only be extended to neighboring areas of Indo-Gangetic Plain but also validated and expanded for use in south and south–east Asian countries with similar soils and cropping systems.

Evaluation of Soil Physical Quality under Amendments and Hydrogel Applications in a Soybean–Wheat Cropping System

A field study was conducted in alluvial sandy loam soil to assess the impact of amendments and hydrogel application on soil hydrophysical properties. Soil physical environment was characterized and quantified using soil physical quality index (S). The main treatments include farmyard manure (FYM) and tank soil applied at 5 t ha−1 and no amendment, and subtreatments included three rates of hydrogel: 5, 2.5, and 0 kg ha−1. Hydrogel was applied at 5–7 cm deep just below the seed in rows. Results revealed that FYM along with gel application at 5 kg ha−1 significantly increased mean weight diameter, field capacity moisture content, plant-available water content and relative field capacity, retention pores (Ret P), water-stable structural units, and structural coefficient and reduced transmission pores (TP), penetration resistance, and saturated hydraulic conductivity (Ks). Significantly greater values of S in hydrogel-treated plots and close associations of S with other soil physical parameters were obtained.

Determination of soil available water for plants: Consistency between laboratory and field measurements

This study was conducted to investigate the consistency between laboratory and field measurements of plant available water (PAW), least limiting water range (LLWR), integral water capacity (IWC) and soil physical quality index (S). It was also intended to propose quick and reliable method(s) for calculation of these indices. The S, PAW, LLWR and IWC of twenty soils were calculated using laboratory and field measurements. The consistency among four laboratory and two field schemes was evaluated to calculate soil available water (SAW). In the laboratory, soil hydraulic properties were determined using sand box and pressure plate apparatuses. Soil penetration resistance (Q) was measured using a cone micro-penetrometer. In the field, soil hydraulic and mechanical properties were determined and/or predicted using the data collected by tensiometers “Tens” or tension/disk infiltrometer “Disk”, and field cone penetrometer, respectively. The SAW and S values were calculated using all laboratory data “Total” which was regarded as benchmark for evaluation of the other schemes. The “SB/FC/PWP” scheme represents laboratory measurements of soil water retention by sand box (SB), field capacity (FC) and permanent wilting point (PWP), and “0/FC/PWP” scheme represents only saturated water content (0), FC and PWP measurements. In general, differences were observed between the water retention curves of different schemes. Also the laboratory-measured Q values were considerably greater than those measured in the field at similar water contents. These dissimilarities caused significant differences between SAW and S values calculated by different schemes. However, there was good compatibility between SAW and S values calculated by “SB/FC/PWP”, “0/FC/PWP” schemes and “Total” scheme suggesting these schemes as the reliable and quick schemes for SAW determination. We also found good compatibility between LLWR and IWC values calculated by “Tens” and “Total” schemes. Using “Tens” scheme, LLWR and IWC could be determined/calculated in the field in about ten days.

Uni and multivariate analyses of soil physical quality indicators of a Cambisol from Apodi Plateau – CE, Brazil

Considering that the conventional tillage changes the soil physical properties in a negative way, and that the use of multivariate statistics provides better perception and interpretation of the interactions between the variables involved in the changes than the univariate does, this study aimed to evaluate soil physical quality indicators through statistical techniques and then infer about the physical quality of the soils. The studied area has been cultivated with pineapple for eight years. Water is supplied through a drip irrigation system and the soil is classified as Cambisol. In order to evaluate soil physical quality, disturbed and undisturbed soil samples were collected in these layers for physical analyses: granulometry, dispersed clay, soil bulk and particle densities, organic carbon, aggregate stability, mean weight diameter and resistance to penetration. A completely randomized design was considered with split-plot treatments 2×3×5 (two soil scenarios: under cultivation and secondary forest; three soil layers: 0.0–0.1, 0.1–0.2 and 0.2–0.3m; five replicates). Statistical tests were used: Kolmogorov–Smirnov to verify data normality, F for variance analysis and Tukey for comparing treatment means, all at 5% of probability. Cluster analysis, principal component analysis and factor analysis were used to better analyze the dataset of the studied variables. As a conclusion, it was refuted the hypothesis of worse physical quality for the soil under conventional pineapple cultivation comparing it to the soil under secondary forest. The multivariate statistical techniques were essential to better understand the set of studied variables and their interaction with soil uses, thus being possible to determine objectively which attributes discriminated each soil use situation and the respective layers. It was also possible to find results not shown by univariate analysis. Therefore, multivariate analysis is recommended as an auxiliary tool in studies to evaluate soil physical quality.

Revisiting the S-index for soil physical quality and its use in Brazil

The S-index was introduced in 2004 in a publication by A.R. Dexter. S was proposed as an indicator of soil physical quality. A critical value delimiting soils with rich and poor physical quality was proposed. At present, Brazil is world leader in citations of Dexter's publication. In this publication the S-theory is mathematically revisited and extended. It is shown that S is mathematically correlated to bulk density and total porosity. As an absolute indicator, the value of S alone has proven to be incapable of predicting soil physical quality. The critical value does not always hold under boundary conditions described in the literature. This is to be expected because S is a static parameter, therefore implicitly unable to describe dynamic processes. As a relative indicator of soil physical quality, the S-index has no additional value over bulk density or total porosity. Therefore, in the opinion of the author, the fact that bulk density or total porosity are much more easily determined than the water retention curve for obtaining S disqualifies S as an advantageous indicator of relative soil physical quality. Among the several equations available for the fitting of water retention curves, the Groenevelt-Grant equation is preferable for use with S since one of its parameters and S are linearly correlated. Since efforts in soil physics research have the purpose of describing dynamic processes, it is the author's opinion that these efforts should shift towards mechanistic soil physics as opposed to the search for empirical correlations like S which, at present, represents far more than its reasonable share of soil physics in Brazil.

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.

Use of penetrometers in agriculture: a review

Soil physical quality can be easily and quickly evaluated by using simple equipment to identify levels of soil compaction. Hence, it is necessary to know the variables responsible for changes in the soil penetration resistance (SPR). The aim of this review is to identify the main factors related to the various equipment used for assessing SPR as a soil physical quality indicator in agriculture. This literature review describes the different types of equipment used and its relationship with SPR. A wide range of procedures, devices, and equipments are available. Much of variability in SPR results is related to the equipment model, cone angle and diameter, and penetration rate. Usually, restrictions to root growth are correlated with SPR values above 2-3 MPa. However, comparisons of SPR values obtained under different soil moisture regimes in the same soil type have provided conflicting results of difficult interpretation. In order to minimize these problems, there is a need for standardization of measurement procedures and interpretation, and/or correction of SPR values according to a soil water content of reference.

Spatial Variability of Physical Soil Quality Index of an Agricultural Field

A field investigation was carried out to evaluate the spatial variability of physical indicators of soil quality of an agricultural field and to construct a physical soil quality index (SQIP) map. Surface soil samples were collected using10 m×10 m grid from an Inceptisol on Ganges Tidal Floodplain of Bangladesh. Five physical soil quality indicators, soil texture, bulk density, porosity, saturated hydraulic conductivity (KS), and aggregate stability (measured as mean weight diameter, MWD) were determined. The spatial structures of sand, clay, andKSwere moderate but the structure was strong for silt, bulk density, porosity, and MWD. Each of the physical soil quality indicators was transformed into 0 and 1 using threshold criteria which are required for crop production. The transformed indicators were the combined into SQIP. The kriged SQIPmap showed that the agricultural field studied could be divided into two parts having “good physical quality” and “poor physical soil quality.”

Variabilidade espacial da produtividade de sorgo e atributos físicos em um Planossolo.

O cultivo do sorgo (Sorghum bicolor L. Moench) para produção de silagem vem aumentado na região Centro-Oeste do Brasil. A capacidade produtiva desta cultura pode ser influenciada pelos atributos físicos do solo, como resistência do solo à penetração - RP; densidade do solo - DS; umidade gravimétrica – UG e umidade volumétrica – UV, os quais estando com valores adequados ao desenvolvimento do sistema radicular, interferem positivamente na produtividade da cultura. Objetivando-se estudar a variabilidade espacial e correlações lineares entre a produtividade do sorgo para forragem e atributos físicos do solo, realizou-se um experimento em um Planossolo na cidade de Miranda, MS. As variáveis analisadas foram biomassa verde da forragem (MVF), RP, UG, UV e DS, coletadas aleatoriamente, em área demarcada com o uso de um receptor GPS, sendo amostrados 51 pontos com espaçamentos irregulares. Os atributos estudados (solo e planta), além de terem correlação espacial, apresentaram variabilidade dos dados entre média e alta e seguiram padrões espaciais bem definidos, com alcance entre 130,0 e 352,0 m. A RP e UG foram bons indicadores da qualidade física do solo, quando destinado à produtividade da MVF de sorgo.

Intervalo hídrico ótimo para avaliação da degradação física do solo

A influência do sistema de uso e manejo na qualidade física do solo tem sido tema de destaque em razão de seus impactos ambientais e agronômicos. O intervalo hídrico ótimo (IHO) é um moderno indicador da qualidade física que potencialmente pode apresentar os mecanismos e processos de perda ou recuperação da qualidade física do solo, por causa do seu uso e manejo. Diante disso, o objetivo deste trabalho foi quantificar a influência de diferentes sistemas de uso e manejo no IHO de um Latossolo Vermelho distrófico, textura franco-arenosa, composto por 170, 40 e 790 g kg-1 de argila, silte e areia, respectivamente. Foram selecionadas quatro áreas, sob os seguintes sistemas de uso e manejo do solo: mata nativa; pastagem cultivada por mais de 20 anos; citros por mais de 10 anos, antecedido por 10 anos de pastagens; e cultivo com culturas comerciais (milho, sorgo, aveia e mandioca), por cerca de 15 anos, após 10 anos de pastagem cultivada. Foram coletadas 48 amostras indeformadas, em cada área, no centro da camada de 0-0,10 m de profundidade. As amostras foram submetidas a potenciais de -10 a -15.000 hPa, em que foram determinadas a curva de retenção de água, a curva de resistência do solo à penetração e, posteriormente, a densidade do solo (Ds) e o IHO. A Ds foi influenciada pelos sistemas de uso e manejo do solo na sequência cultivo = citros > pastagem > mata nativa. A relação entre IHO e Ds foi linear e negativa, à exceção da mata nativa que na faixa de Ds entre 1,35-1,55 Mg m-3 apresentou relação positiva. Valores de Ds, em que o IHO = 0, associados com severa degradação física do solo, foram de 1,75 e 1,80 Mg m-3, nos solos sob citros e cultivo, respectivamente; a proporção desses valores foi de 21 % para o solo sob citros e 18 %, para o sob cultivo. A perda de qualidade física do solo foi menos acentuada no solo sob pastagem, quando comparado com os solos sob citros e cultivo, sendo a diminuição do IHO menos acentuada com o aumento da Ds. O menor valor de Ds em que iniciou a redução do IHO foi tomado como densidade do solo de alerta (Ds a). A Ds a foi de 1,55 Mg m-3 e pode ser utilizada como valor de referência no processo de recuperação da qualidade física do solo, válida para solos com textura, uso e manejo semelhante ao deste estudo.

Реєстр еталонних параметрів фізичної якості орних ґрунтів України

The algorithm has been developed and creation of the register for standard physical parameters of the mane arable soils has been started on the basis of a multipurpose database of relational type “Ukrainian soil properties”. Soils are positioned in space of provinces of nature-agricultural zoning of Ukraine. The purpose of work is an estimation of soil physical quality. Calculations of the integrated index of soil physical quality are carried out according to the way developed by authors. The method is based on definition of soil physical quality on 7 basic physical properties. Nature-agricultural zoning is a spatial basis, and a province – the smallest spatial unit. Soil physical quality for different types has been compared in borders of each province by relative criteria. Key words: soil physical quality index; standard; nature-agricultural zoning; province.

Implications of plant cover in the structure of a clayey oxisol under no-tillage

Knowledge of indicators of soil physical quality is of paramount importance for better understanding of soil-plant relationships. These indicators include the bulk density and soil resistance to penetration. The objective of this study was to evaluate the use of four cover crop species in the process of reducing the soil density and its resistance to penetration in areas managed under no-tillage system. The species denominated “revitalizers” of the soil structure were considered as treatments: Dolichos lab lab , Mucuna aterrimum, Sorghum bicolor and Mucuna aterrima , in addition to the witness (without cultivation). Soil samples were taken from the bulk density 0.0 to 0.1, 0.1 to 0.2, and of 0.2 to 0.3 m depth under two collection conditions, row and inter-row. Soil resistance to penetration was determined by penetrometer, with electronic data storage. We considered two experimental designs 5 × 3 × 2 and 5 × 4 × 2 factorial with five treatments (four species of area coverage and fallow); three depths of soil bulk density and four depths for penetration resistance, two conditions of collection. The statistical data provided was based on the analysis of variance and the treatment means were compared by the Tukey test at 5% significance. The evaluated species, specially the S. bicolor, the D. lab lab and the M. aterrima , presented a promissory effect for the improvement of the structural state of the soil in comparison to the area without cultivation. Keywords : Compaction, soil resistance, bulk density African Journal of Biotechnology Vol. 12(24), pp. 3807-3810

Physical quality of a podzolic soil following 19 years of irrigated minimum-till kikuyu-ryegrass pasture

Dairy production from planted pastures is one of the main farming systems in the southern Cape region of South Africa. Large tracts of natural rangeland were converted to planted pastures for increased fodder production. To sustain these agro-ecosystems, the physical condition of soil needs to be protected. The objective of this study was to assess the impact that conversion of natural rangeland to planted pastures had on the physical condition of a sandy soil after 19 years. An irrigated minimum-till kikuyu (Pennisetum clandestinum)-ryegrass (Lolium spp.) pasture soil was compared with a virgin fynbos soil. Physical indicators of soil quality were measured at 0–100mm, 100–200mm and 200–300mm depth intervals. The planted pasture was highly productive, in comparison to the natural vegetation. Clay content was similar (P≤0.01) between sites within the 0–100mm and 100–200mm depths and comparison of indicators between sites and interpretation thereof should be unbiased for those depths. Penetration resistance and to a lesser extent also bulk density of the planted pasture soil showed that conversion of virgin soil to minimum-till pastures adversely affected soil physical resistance by increased compaction. Aggregate stability (water stable aggregate percentage) was higher (P≤0.05) in the 0–100mm and 100–200mm layers of virgin soil and the soil microstructure was adversely affected with a lower water stable aggregate percentage in planted pasture soil compared to that of the virgin soil. Infiltration rate did not differ between sites. In comparison to fynbos vegetation, planted pasture increased water holding capacity of the 0–100mm layer by 5.0% (P≤0.01), but did not affect (P>0.01) water holding capacity in the 100–200mm and 200–300mm layers. Conversion of virgin soil to minimum-till kikuyu-ryegrass pasture degraded the dynamic physical condition of a podzolic soil over 19 years in terms of physical resistance and soil microstructure strength, but enhanced water holding capacity and maintained infiltration rate.