Mechanical stresses on an expanding cylindrical root analog in antigranulocytes media

Richards, B G; Greacen, EL

doi:10.1071/sr9860393

Cited by 61 publications

(35 citation statements)

References 14 publications

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“…First, in an homogeneous soil considered as an elasto-plastic medium, finite-element analyses have shown that a radial increase of the root will relieve axial stress ahead of the root tip [113][114][115]. This mechanism which reduces the axial resisting pressure of the soil helps the root to continue to grow straight along its axis.…”

Section: C) Does Root Thickening Optimize Penetration?mentioning

confidence: 99%

Physical root–soil interactions

2017

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Abstract. Plant root system development is highly modulated by the physical properties of the soil and especially by its mechanical resistance to penetration. The interplay between the mechanical stresses exerted by the soil and root growth is of particular interest for many communities, in agronomy and soil science as well as in biomechanics and plant morphogenesis. In contrast to aerial organs, roots apices must exert a growth pressure to penetrate strong soils and reorient their growth trajectory to cope with obstacles like stones or hardpans or to follow the tortuous paths of the soil porosity. In this review, we present the main macroscopic investigations of soil-root physical interactions in the field and combine them with simple mechanistic modeling derived from model experiments at the scale of the individual root apex.2

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Section: C) Does Root Thickening Optimize Penetration?mentioning

confidence: 99%

Physical root–soil interactions

2017

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“…These are root dimensions (length, diameter, surface area) which affect the requirements of carbon (Eissenstat 1992), nutrient and water uptake (Barber and Silberbush 1984), ability to penetrate into soil (Richards andGreacen 1986, Materechera et al 1991) and capacity to maximize root to soil contact area ).…”

Section: Efficiency Of Root Systemmentioning

confidence: 99%

“…Gill and Bolt 1955, Misra et al 1986). Radial expansion of a root behind the tip causes a lowering of external mechanical impedance ahead of the elongating root (Abdalla et al 1969, Richards andGreacen 1986).…”

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Effect of soil compactness on the growth and quality of carrot

Pietola¹

1995

AFSci

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Field experiments were performed in Southern Finland on three soil types: fine sand (1989-1991), clay (1989) and mull (1990-1991). The following soil mechanical treatments were applied to autumn ploughed land: soil loosening by ridge preparation (ridge distance 45 cm), rotary harrowing (to a depth of 20 cm, clay 15 cm), and soil compaction track by track by a tractor weighing 3 Mg (1 or 3 passes, wheel width 33 cm) before seed bed preparation. One plot was untreated. These treatments were set up in April (on clay in May) under moist soil conditions. Sprinkler irrigation (one application of 30 mm) was applied to clay and fine sand when soil moisture in top soil had decreased to around 50% of plant-available water capacity. PVC cylinders (r = 15 cm, h = 60 cm) were fixed in the experimental areas during the growing periods. At harvest, these cylinders were removed for specific analysis of tap and fibrous roots of carrot. Length and width of fibrous roots were quantified by image analysis in the USA. The impacts of soil loosening and partial compaction were determined by measuring soil physical parameters to a depth of 25 cm in mineral soils, and to greater depths in organic soil. Dry bulk densities of the plough layers increased with increasing tractor passes by 8%, 10% and 13% for fine sand, mull and clay soils, respectively. The lowest dry soil bulk density in the plough layer was obtained by rotary harrowing to a depth of 20 cm. Comparison of gamma ray transmission and gravimetric analysis indicated that dry soil bulk density was slightly lower when determined by gravimetric analysis. Increased soil bulk densities were reflected by increased water retention capacity (matric suction ≤ 10 kPa) and greater penetrometer resistance. Relatively similar increases in bulk density increased the penetrometer resistance much less in mull than in fine sand. In contrast, greater bulk densities in the mull soil affected soil air composition adversely by decreasing the O2 content to 10% when the subsoil had high wetness. In other soils, the lowest soil oxygen contents of 16-18% were recorded in early summer (compacted clay) and during periods of vigorous plant growth (fine sand) when soil water contents were high. Even though the highest degree of soil compactness (D) in a plough layer approached 93 (gravimetric) in all soils, only clay soil was compacted to a soil macro-porosity below 10% (pore diameter > 30 μm). Soil compaction promoted crop establishment and early growth as compared with loose soil beds. Optimum soil compactness for carrot yield (D = 82) was observed only in clay field where excess loosening or compaction affected yield quantity adversely at different stages of growth. During biomass accumulation, excessive penetrometer resistances limited tap root growth in compacted fine sand without irrigation. Water applications promoted shoot growth, but did not affect final shoot and tap root yield. Among the three soil types tested in this study, compaction of mull soil had the least effect on carrot growth and external quality. This paper presents evidence that the internal quality of carrots is only slightly affected by changes in soil physical properties, while the adverse effects of soil compaction on carrot external quality (short, deformed and conical tap roots with greater maximum diameters) are clear. Even though compacted clay soil greatly limited the biomass accumulations in the tap root, which had a high crude fibre content, the carotene (10 mg/100 g carrots) and sugar contents (5%) reached acceptable levels. The lowest carotene contents (4 mg/100 g carrots) were observed in loose mull, following a cool late summer in 1990. The effect of irrigation on carotene content varied from one year to another. High sugar and carotene contents appeared to respond to the high below-ground absorption surface. The fibrous root system of carrots, consisting of mostly very fine roots (diameter 0.15 mm), had total lengths of 150 m in loose fine sand at a soil depth of 0-50 cm (rotary harrowed), 200 m and 300 m in fine sand and mull soils subjected to 3 passes by a tractor wheel. The maximum dry weight (60 μg), length (1.2 cm) and surface area (0.05 cm2) of the fibrous root system per soil volume (cm3) were observed in compacted or irrigated soil to a depth of 30 cm, and also in relation to tap root dry weight. This suggests a capacity of carrot plant for high below-ground absorption potential and optimal biochemial maturation of tap root tissue even when surface soils are compacted. This is supported by higher leaf area, as the early shoot growth was promoted by partial soil compaction. Soil compaction affected the soil physical properties and carrot external quality in agreement with previous studies. Carotene and sugar contents appeared to be unaffected or were slightly increased in riper and firmer carrots of compacted soils. This is consistent with the earlier information about the internal quality of carrot which is shown to be highly dependent on genetic factors and developmental stage of carrot. The present study emphasizes the surface area of carrot fibrous root system as a beneficial factor for maintaining high levels of carotene and sugar contents in tap roots after partial soil compaction.

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“…Soil strength, as measured by a PEN (units = 1 kg•cm -2 = 98.1 kPa = 0.0981 MPa = 14.2 psi), is related crudely to soil resistance as encountered by roots. Maximum root pressure of many plants to expand in soil lies between 0.9-1.3 MPa (Richards and Greacen 1986). Sands et al (1979) report that root penetration of radiata pine (Pinus radiata D. Don) in sandy soils in South Australia was severely restricted at 3.0 MPa resistance.…”

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Precision, accuracy, and efficiency of four tools for measuring soil bulk density or strength.

Miller¹,

Hazard²,

Howes³

2001

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AuthorsMonitoring soil compaction is time consuming. A desire for speed and lower costs, however, must be balanced with the appropriate precision and accuracy required of the monitoring task. We compared three core samplers and a cone penetrometer for measuring soil compaction after clearcut harvest on a stone-free and a stony soil. Precision (i.e., consistency) of each tool at depths of 0-10, 10-20, and 20-30 cm was determined from two adjacent samples at 21 or more sampling points in each harvested location. Because one bulk density (D b ) sampler provided a continuous sample of each decimeter depth, it was designated as the standard; thereby, the relative accuracy and bias of the two shorter core samplers could be calculated. Both shorter samplers overestimated D b as determined by the standard. At least 15 penetrometer samples could be taken and processed in the time required for three D b samples to the same 30-cm depth. Precision of measurements taken by the cone penetrometer, however, was clearly less than that with any of the D b samplers. Based on time requirements and precision of each tool, we examined the efficiency of double sampling (using a combination of penetrometer and core sampler) for estimating D b . Results from the stone-free soil indicated an advantage in both precision and efficiency in applying double-sampling theory to estimate D b rather than sampling exclusively by the more time-consuming core samplers.Keywords: Bulk density, measurement precision, relative accuracy, cone penetrometer, soil strength. SummarySoil bulk density (D b ) is the ratio of mass of dry solids to bulk volume of soil. Bulk density, expressed as Mg•m -3 or g•cc -1 , is commonly used to measure soil compaction. An increase in D b indicates that movement of air and water within the soil has been reduced, and that the soil may be less favorable for plant growth or be more likely to erode. Soil compaction also can be indicated by a penetrometer (PEN), a device forced into the soil to measure its resistance to vertical penetration. Soil strength, as measured in kPa by a PEN, is related crudely to soil resistance as encountered by roots. Because PEN readings can be strongly dependent on soil moisture content, field sampling for comparative purposes should be done when soils are near field capacity.Our general objective was to compare precision and efficiency of four tools conventionally used to monitor soil compaction. We compared three bulk density samplers and a cone penetrometer for measuring soil compaction over a range of sampling conditions in two young forests. Both stands had been planted after clearcutting and yarding by crawler tractors (D-8) in winter on wet silt loam soils. Both study locations were sampled during the spring rainy season; therefore, soils were probably at or near field capacity. Sampling points for each tool were assigned by subdividing each potential sampling plot, a 25-x 100-cm rectangle, into four equal-sized squares and randomly allocating a tool to each square. Two subsamples (replica...

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Mechanical stresses on an expanding cylindrical root analog in antigranulocytes media

Cited by 61 publications

References 14 publications

Physical root–soil interactions

Physical root–soil interactions

Effect of soil compactness on the growth and quality of carrot

Precision, accuracy, and efficiency of four tools for measuring soil bulk density or strength.

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