Effects of soil bulk density and water regimen on root growth and uptake of phosphorus by ryegrass

Cornish, PS; So, H. B.; McWilliam, JR

doi:10.1071/ar9840631

Cited by 47 publications

(25 citation statements)

References 21 publications

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“…This is a direct consequence of the decrease in root growth and probably in diffusion coefficient of P, due to high tortuosity. The results are in agreement with previous reports (Castilo et al, 1982;Cornish et al, 1984;Dolan et al, 1992). However, increasing soil compaction increased P uptake per unit length of root.…”

Section: Discussionsupporting

confidence: 83%

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The effect of soil compaction on growth and P uptake by Trifolium subterraneum: interactions with mycorrhizal colonisation

et al. 1996

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The effects of vesicular-arbuscular mycorrhizal (VAM) colonisation on phosphorus (P) uptake and growth of clover (Trifolium subterraneum L.) in response to soil compaction were studied in three pot experiments. P uptake and growth of the plants decreased as the bulk density of the soil increased from 1.0 to 1.6 Mg m -3. The strongest effects of soil compaction on P uptake and plant growth were observed at the highest P application (60 mg kg-1 soil). The main observation of this study was that at low P application (15 mg kg -l soil), P uptake and shoot dry weight of the plants colonised by Glomus intraradices were greater than those of non-mycorrhizal plants at similar levels of compaction of the soil. However, the mycorrhizal growth response decreased proportionately as soil compaction was increased. Decreased total P uptake and shoot dry weight of mycorrhizal clover in compacted soil were attributed to the reduction in the root length. Soil compaction had no significant effect on the percentage of root length colonised. However, total root length colonised was lower (6.6 m pot-l) in highly compacted soil than in slightly compacted soil (27.8 m pot-z). The oxygen content of the soil atmosphere measured shortly before the plants were harvested varied from 0.18 m3m -3 in slightly compacted soil (1.0 Mg m -3) to 0.10 m3m -3 in highly compacted soil (1.6 Mg m-3).

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Section: Discussionsupporting

confidence: 83%

“…However, increasing soil compaction increased P uptake per unit length of root. This may be attributed to the increased mass of P within the root depletion zone resulting from compacting the soil (Cornish et al, 1984). Moreover, the increased root diameter may increase P uptake per unit length of root from compacted soil.…”

Section: Discussionmentioning

confidence: 99%

The effect of soil compaction on growth and P uptake by Trifolium subterraneum: interactions with mycorrhizal colonisation

et al. 1996

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“…In the case of hard soil, there may be a depletion of the small reservoir of water and nutrients available to a root system which has explored a small volume of soil. Poor growth in soft soil may have been due to the depletion of immobile nutrients in the immediate vicinity of the root, as a consequence of the low soil mass per unit volume (Cornish et al, 1984), or because the movement of water and nutrients into the root was impeded by poor root-soil contact (Herkelrath et al, 1977;. Our theoretical calculations suggest that, in wet soil, the supply of water to barley leaves would not be greatly affected by either the very soft or hard soil treatment (Figure 7), although the assumptions that the calculations were based on would be difficult to test, and direct water potential or turgor measurements were not made.…”

Section: Discussionmentioning

confidence: 99%

Soil structure and plant growth: Impact of bulk density and biopores

Stirzaker

Passioura

Wilms³

1996

Plant Soil

265

163

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Compacted soils are not uniformly hard; they usually contain structural cracks and biopores, the continuous large pores that are formed by soil fauna and by roots of previous crops. Roots growing in compacted soils can traverse otherwise impenetrable soil by using biopores and cracks and thus gain access to a larger reservoir of water and nutrients. Experiments were conducted in a growth chamber to determine the plant response to a range of uniform soil densities, and the effect of artificial and naturally-formed biopores. Barley plants grew best at an intermediate bulk density, which presumably represented a compromise between soil which was soft enough to allow good root development but sufficiently compact to give good root-soil contact. Artificial 3.2 mm diameter biopores made in hard soil gave roots access to the full depth of the pot and were occupied by roots more frequently than expected by chance alone. This resulted in increased ~plant growth in experiments where the soil was allowed to dry. Our experiments suggest that large biopores were ~ not a favourable environment for roots in wet soil; barley plants grew better in pots containing a network of narrov~ biopores made by lucerne and ryegrass roots, responded positively to biopores being filled with peat, and some pea radicles died in biopores. A theoretical analysis of water uptake gave little support to the hypothesis that water supply to the leaves was limiting in either very hard or very soft soil. The net effect of biopores to the plant would be the benefits of securing extra water and nutrients from depth, offset by problems related to poor root-soil contact in the biopore and impeded laterals in the compacted biopore walls.

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“…This could be significant for nutrient uptake, particularly for slowly diffusing nutrients like phosphorous where uptake is a function of root extension rate (Cornish et al, 1984). Slow root growth should reduce P uptake from the soil matrix.…”

Section: Discussionmentioning

confidence: 99%

“…1) leaving gas-filled porespace of 12%. Now, the average diameter of seminal roots of ryegrass is 0.3 mm (Cornish et al, 1984) which is the effective diameter of pores drained at 1 kPa suction. Thus, potentially 12% of the porespace was accessible to ryegrass roots of 0.3 mm diameter without the need for deforming the soil.…”

Section: Discussionmentioning

confidence: 99%

Soil macrostructure and root growth of establishing seedlings

Cornish

1993

Plant Soil

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The importance of macrostructure to root growth of ryegrass (L. perenne) seedlings sown on the soil surface was studied in two soils in which the macrostructure had resulted mainly from root growth and macro-faunal activity. Sets of paired soil cores were used, one of each pair undisturbed and the other ground and repacked to the field bulk density.Undisturbed and repacked soils were first compared at equal water potentials in the range -1 . 9 to -3 0 0 kPa. At equal water potential, the undisturbed soil always had the greater strength (penetration resistance), and root growth was always greater in the repacked soil with no macrostructure than it was in the soil with macrostructure intact. At equal high strength (low water potentials) it appeared that root growth was better when soils were structured. When strength was low (high water potentials), root growth was better in the unstructured soil.Soils were then compared during drying cycles over 21 days. The average rate at which roots grew to a depth of 60 mm, and also the final percentage of plants with a root reaching 60 mm depth, was greatest in repacked soils without macrostructure. The species of vegetation growing in the soil before the experiment affected root growth in undisturbed soil; growth was slower where annual grasses and white clover had grown compared with soil which had supported a perennial grass.It appears that relatively few roots locate and grow in the macrostructure. Other roots grow in the matrix, if it is soft enough to be deformed by roots. Roots in the matrix of a structured soil grow more slowly than roots in structureless soil of equal bulk density and water potential. The development of macrostructure in an otherwise structureless soil, of the type studied, is of no advantage to most roots. However, once a macrostructure has developed, the few roots locating suitable macropores are able to grow at low water potential when soil strength is high. The importance of macrostructure to establishing seedlings in the field lies in rapid penetration of at least a few roots to a depth that escapes surface drying during seasonal drought.

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Effects of soil bulk density and water regimen on root growth and uptake of phosphorus by ryegrass

Cited by 47 publications

References 21 publications

The effect of soil compaction on growth and P uptake by Trifolium subterraneum: interactions with mycorrhizal colonisation

The effect of soil compaction on growth and P uptake by Trifolium subterraneum: interactions with mycorrhizal colonisation

Soil structure and plant growth: Impact of bulk density and biopores

Soil macrostructure and root growth of establishing seedlings

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