Jerzy Lipiec

A review of the usefulness of relative bulk density values in studies of soil structure and compaction

The state of compactness is an important soil structure and quality attribute, and there is a need to find a parameter for its characterization that gives directly comparable values for all soils. The use of some relative bulk density value for this purpose, particularly the degree of compactness (Hakansson, 1990), is discussed in this review. The degree of compactness has been defined as the dry bulk density of a soil as a percent of a reference bulk density obtained by a standardized uniaxial compression test on large samples at a stress of 200 kPa. The bulk density should be determined at standardized moisture conditions, to prevent problems caused by water content variations in swelling/shrinking soils. The degree of compactness (D) makes results of soil compaction experiments more generally applicable. Whereas the bulk density or porosity optimal for crop growth vary greatly between soils, the optimal D-value is virtually independent of soil composition. Critical limits of penetration resistance (3 MPa) and air-filled porosity (10%, v/v) are similarly related to the D-value and matric water tension in most soils. As the D-value increases above the optimal, the tension range offering non-limiting conditions becomes increasingly limited. The D-value of the plough layer induced by a given number of passes by a certain vehicle is similar in all soils, provided the moisture conditions are comparable. The degree of compactness facilitates modelling of soil and crop responses to machinery traffic. Although this parameter was primarily introduced for use in annually disturbed soil layers, its use may be extended to undisturbed soil layers.

Quantification of compaction effects on soil physical properties and crop growth

Abstract A quantitative description of soil compaction effects is required to improve soil management for reducing compaction problems in crop production and environment. Our objective is to provide a review of indices and methods used to quantify the effects of compaction on soil physical properties and crop growth. The paper starts with the description of available methods to quantify stress and displacement under traffic. The following few sections deal with methods and parameters used to characterise the effect of compaction on soil strength, oxygen, water, heat and structural arrangement with consideration of spatial variability. The effect of soil compaction on macroporosity and associated water movement, aeration and root growth is discussed. One section is devoted to integrated systems to measure simultaneously more than one soil physical property. Potential of some advanced developments in computer-assisted tomography (CAT) and nuclear magnetic resonance (NMR) for non-destructive 3D quantification of soil structure, roots and root water uptake as affected by soil compaction is indicated. Finally, some techniques useful for quantifying root and shoot growth, and water uptake in relation to soil compaction are discussed. The models available allow assessment of compaction effects on some behavioural soil properties based on the inherent properties and bulk density of soil. Additional research is required on the effect of compaction on soil structural discontinuities that substantially affect many soil functions and root growth in the whole profile.

Effects of soil compaction and tillage systems on uptake and losses of nutrients

Abstract In the framework of research on the environmental consequences of soil compaction, the impact of soil compaction and tillage systems on uptake and losses of nutrients, in particular nitrogen, are discussed. Evidence is presented to indicate interactive relationships between the amount of soil compaction, root growth, soil water and soil aeration status, and nutrient supply and uptake by plants. The importance of soil structure and pore size distribution in influencing the transport of nutrients in compacted soil is illustrated. Emphasis is given to the negative effects of soil compaction on components of the environment due to nutrient leaching, surface runoff and gaseous losses to the atmosphere.

Soil physical properties and growth of spring barley as related to the degree of compactness of two soils

Abstract The relationships between the degree of compactness of soil and soil penetration resistance, air-filled porosity, temperature and root development, leaf area index (LAI) and yield of spring barley were studied. The data were obtained from field experiments on a silty loam and a loamy sand, with five wheel-compaction treatments prior to sowing in 1986–1989. An increase in the degree of compactness resulted in higher penetration resistance, lower air-filled porosity and smaller daily temperature fluctuations, a greater accumulation of roots in the topsoil and shallower rooting depth. The LAI and grain yields decreased sharply when the degree of compactness exceeded ≈88%.

Effect of drought and heat stresses on plant growth and yield: a review

Abstract Drought and heat stresses are important threat limitations to plant growth and sustainable agriculture worldwide. Our objective is to provide a review of plant responses and adaptations to drought and elevated temperature including roots, shoots, and final yield and management approaches for alleviating adverse effects of the stresses based mostly on recent literature. The sections of the paper deal with plant responses including root growth, transpiration, photosynthesis, water use efficiency, phenotypic flexibility, accumulation of compounds of low molecular mass (eg proline and gibberellins), and expression of some genes and proteins for increasing the tolerance to the abiotic stresses. Soil and crop management practices to alleviate negative effects of drought and heat stresses are also discussed. Investigations involving determination of plant assimilate partitioning, phenotypic plasticity, and identification of most stress-tolerant plant genotypes are essential for understanding the complexity of the responses and for future plant breeding. The adverse effects of drought and heat stress can be mitigated by soil management practices, crop establishment, and foliar application of growth regulators by maintaining an appropriate level of water in the leaves due to osmotic adjustment and stomatal performance.

Critical soil bulk density and strength for pea seedling root growth as related to other soil factors

Bulk density and soil strength are two major soil physical factors affecting root growth of pea seedlings. This study was conducted to determine the influence of soil texture, organic carbon content and water content on critical bulk density and strength. Soil from the plough layer (PL) and beneath the sub-soil (SUB) was used. By soil packing and adjusting the water content between 30% and 100% of field water capacity (FWC) a wide range of bulk density (1.3-1.7 Mg m -3 ) and strength (0.24-6.66 MPa) were obtained. Pea (Pisum sativum L.) was grown in the packed cores of 100 cm 3 for 72 h at 20°C. Regression models were developed to explain root growth in terms of bulk density, soil strength, silt and clay (<60 μm) content, organic carbon, and water content. The regression curve of root growth as a function of soil strength showed that 40% of maximum root length can be regarded as an indicator of very poor root growth. By substituting this value into the root growth equations we calculated a critical bulk density and strength in terms of fraction<60 μm, organic carbon percentage and water content. The values of critical bulk density in both layers and of critical soil strength in the sub-soil increased with a decreasing content of fraction<60 μm. Irrespective of fraction<60 μm content, the critical bulk density and strength decreased as soil water content decreased. Critical soil strength was more sensitive than critical bulk density to changes in fraction<60 μm content and water content. This study provides data and a method for predicting critical bulk density and soil strength in relation to other soil properties for pea seedling root growth.

Community Level Physiological Profiles (CLPP), Characterization and Microbial Activity of Soil Amended with Dairy Sewage Sludge

The aim of the present work was to assess the influence of organic amendment applications compared to mineral fertilization on soil microbial activity and functional diversity. The field experiment was set up on a soil classified as an Eutric Cambisol developed from loess (South-East Poland). Two doses of both dairy sewage sludge (20 Mg·ha−1 and 26 Mg·ha−1) and of mineral fertilizers containing the same amount of nutrients were applied. The same soil without any amendment was used as a control. The soil under undisturbed native vegetation was also included in the study as a representative background sample. The functional diversity (catabolic potential) was assessed using such indices as Average Well Color Development (AWCD), Richness (R) and Shannon–Weaver index (H). These indices were calculated, following the community level physiological profiling (CLPP) using Biolog Eco Plates. Soil dehydrogenase and respiratory activity were also evaluated. The indices were sensitive enough to reveal changes in community level physiological profiles due to treatment effects. It was shown that dairy sewage amended soil was characterized by greater AWCD, R, H and dehydrogenase and respiratory activity as compared to control or mineral fertilized soil. Analysis of variance (ANOVA) and principal component analysis (PCA) were used to depict the differences of the soil bacterial functional diversity between the treatments.

Influences of degree of compactness and matric water tension on some important plant growth factors

The degree of compactness (D) has been defined earlier as the dry bulk density of a soil in percent of a reference bulk density obtained by a standardized uniaxial compression test on large samples at a stress of 200 kPa. It was primarily aimed for use in annually disturbed soil layers. Field experiments have demonstrated its usefulness for characterizing the state of compactness from a crop production point of view, but knowledge is lacking regarding the relation between D and various plant growth factors. While the bulk density or porosity optimal for crop growth has varied considerably between soils, the optimal D-value has been virtually independent of soil texture. This led to a hypothesis that critical limits of penetration resistance (3 MPa) and air-filled porosity (10%, v/v) are similarly related to the D-value in most soils. With the objective to test this hypothesis, the positions of these limits as functions of the D-value and the matric water tension were studied in four soils with clay content ranging from 70 to 220 g kg−1. In all of them, the positions of the critical limits were similar. The higher the D-value, the more limited was the tension range offering adequate conditions for crop growth, the higher was the water tension (the lower the water content) at which aeration became critical, and the lower was the water tension (the higher the water content) at which penetration resistance became critical. The effects of critical soil conditions were reflected in increased stomatal resistance of plants grown in soil with a high D-value. The results provide basic information for modeling the relationships between soil compactness and plant growth.

Review of modelling crop growth, movement of water and chemicals in relation to topsoil and subsoil compaction

Soil compaction influences crop growth, movement of water and chemicals in numerous ways. Mathematical modelling contributes to better understanding of the complex and variable effects. This paper reviews models for simulating topsoil and subsoil compaction effects. The need for including both topsoil and subsoil compaction results from still increasing compactive effect of vehicular pressure which penetrates more and more into the subsoil and which is very persistent. The models vary widely in their conceptual approach, degree of complexity, input parameters and output presentation. Mechanistic and deterministic models were most frequently used. To characterise soil compactness, the models use bulk density and/or penetration resistance and water content data. In most models root growth is predicted as a function of mechanical impedance and water status of soil and crop yield-from interactions of soil water and plant transpiration and assimilation. Models for predicting movement of water and chemicals are based on the Darcy/Richards one-dimensional flow equation. The effect of soil compaction is considered by changing hydraulic conductivity, water retention and root growth. The models available allow assessment of the effects of topsoil and subsoil compaction on crop yield, vertical root distribution, chemical movement and soil erosion. The performance of some models was improved by considering macro-porosity and strength discontinuity (spatial and temporal variability of material parameters). Scarcity of experimental data on the heterogeneity is a constraint in modelling the effects of soil compaction. Suitability of most models was determined under given site conditions. Few of the models (i.e. SIBIL and SIMWASER) were found to be satisfactory in modelling the effect of soil compaction on soil water dynamics and crop growth under different climate and soil conditions.

Measurement of plant water use under controlled soil moisture conditions by the negative pressure water circulation technique

Abstract A negative pressure water circulation system was developed so as to supply water quantitatively to a water-consuming soil column while maintaining the matric potential of soil water constant. The system consisted of a vacuum chamber with an air pressure gauge, a vacuum pump with a magnetic valve, a water reservoir with a scale, a motor for the circulation of water, a porous ceramic tube, and Tygon tubes to connect the components. Usefulness of the technique for the measurement of the water uptake by intact roots was tested for maize growing on a clayey soil. The soil packed in polyvinyl chloride cylinders (7.5 cm i.d. and 5 cm deep) was treated as follows; non-compacted (bulk density 1.0 g·cm-3), compacted (BD 1.3 g·cm-3), compacted plus 20 holes 1.2 mm in diameter, and compacted plus 20 holes 2.0 mm in diameter. The ceramic tube which supplied water circulating under the pressure of -9.7 (experiment I) or -24.3 kPa (experiment II) was embedded in the center of the treated soil. Maize seedlings w...