Improved soil fertility from compost amendment increases root growth and reinforcement of surface soil on slopes

Suzanne Donn; Ron E. Wheatley; Blair M. McKenzie; Kenneth W. Loades; Paul D. Hallett

doi:10.1016/j.ecoleng.2014.07.066

Improved soil fertility from compost amendment increases root growth and reinforcement of surface soil on slopes

Suzanne Donn, Ron E. Wheatley, Blair M. McKenzie, Kenneth W. Loades, Paul D. Hallett^*

^*Corresponding author for this work

Aberdeen Centre For Environmental Sustainability

Research output: Contribution to journal › Article › peer-review

69 Citations (Scopus)

Abstract

Vegetation such as grasses and shrubs can improve slope stability, reducing the risk of shallow failures once roots have permeated soil to enhance cohesion. However, establishment of vegetation is hindered by poor soil fertility, frequently a characteristic of disturbed soils used in engineering projects. We evaluated whether compost could improve the rate of vegetation establishment and hence soil mechanical reinforcement by plant roots and therefore protect against shallow failures. Over 1200t of material was formed into a slope 40m long×15m wide, with an experimental soil slope angle of 20°. Washings from recycled mineral fill were used for the surface soil. Five amendment treatments were replicated three times in strips of 1.5m by 8m in a randomised block design on this slope; treatments were a no compost control, standard compost addition at a rate of 35tha^-1 and a high level compost amendment at 300tha^-1, applied either to the surface or incorporated into the topsoil to 10cm.Thirteen weeks after planting an amenity grass mix, vegetation cover increased up to 6 times compared to the control for 35tha^-1 surface applied compost and similarly 20 times for 300tha^-1 compost that had been surface applied. Root length density was about 3kmm^-3 with no added compost and about 30kmm^-3 for 300tha^-1 added compost. At 35tha^-1 compost, peak shear stress of the vegetated soil at 5cm depth was not affected, but it almost doubled with 300tha^-1 compost compared to no amendment. Cohesion from plant roots was 8.1kPa for 300tha^-1, in comparison to 2.1kPa for no amendment and 2.3kPa for 35tha^-1 compost. Whereas surface application resulted in better vegetation cover, there were no differences in peak shear stress between plots with surface application or incorporation of compost. This study provided experimental evidence in the field that compost improvement to soil fertility has a positive impact on soil stabilisation by plant roots.

Original language	English
Pages (from-to)	458-465
Number of pages	8
Journal	Ecological Engineering
Volume	71
Early online date	15 Aug 2014
DOIs	https://doi.org/10.1016/j.ecoleng.2014.07.066
Publication status	Published - Oct 2014

Bibliographical note

Funding Information:
This study was funded by WRAP (Project code: OBF009-047). The James Hutton Institute receives funding from the Rural and Environment Science and Analytical Services Division (RESAS) of the Scottish Government.

Keywords

Compost
Ecoengineering
Root reinforcement
Slope
Soil physics

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10.1016/j.ecoleng.2014.07.066

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title = "Improved soil fertility from compost amendment increases root growth and reinforcement of surface soil on slopes",

abstract = "Vegetation such as grasses and shrubs can improve slope stability, reducing the risk of shallow failures once roots have permeated soil to enhance cohesion. However, establishment of vegetation is hindered by poor soil fertility, frequently a characteristic of disturbed soils used in engineering projects. We evaluated whether compost could improve the rate of vegetation establishment and hence soil mechanical reinforcement by plant roots and therefore protect against shallow failures. Over 1200t of material was formed into a slope 40m long×15m wide, with an experimental soil slope angle of 20°. Washings from recycled mineral fill were used for the surface soil. Five amendment treatments were replicated three times in strips of 1.5m by 8m in a randomised block design on this slope; treatments were a no compost control, standard compost addition at a rate of 35tha-1 and a high level compost amendment at 300tha-1, applied either to the surface or incorporated into the topsoil to 10cm.Thirteen weeks after planting an amenity grass mix, vegetation cover increased up to 6 times compared to the control for 35tha-1 surface applied compost and similarly 20 times for 300tha-1 compost that had been surface applied. Root length density was about 3kmm-3 with no added compost and about 30kmm-3 for 300tha-1 added compost. At 35tha-1 compost, peak shear stress of the vegetated soil at 5cm depth was not affected, but it almost doubled with 300tha-1 compost compared to no amendment. Cohesion from plant roots was 8.1kPa for 300tha-1, in comparison to 2.1kPa for no amendment and 2.3kPa for 35tha-1 compost. Whereas surface application resulted in better vegetation cover, there were no differences in peak shear stress between plots with surface application or incorporation of compost. This study provided experimental evidence in the field that compost improvement to soil fertility has a positive impact on soil stabilisation by plant roots.",

keywords = "Compost, Ecoengineering, Root reinforcement, Slope, Soil physics",

author = "Suzanne Donn and Wheatley, {Ron E.} and McKenzie, {Blair M.} and Loades, {Kenneth W.} and Hallett, {Paul D.}",

note = "Funding Information: This study was funded by WRAP (Project code: OBF009-047). The James Hutton Institute receives funding from the Rural and Environment Science and Analytical Services Division (RESAS) of the Scottish Government.",

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AU - Wheatley, Ron E.

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AU - Loades, Kenneth W.

AU - Hallett, Paul D.

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N2 - Vegetation such as grasses and shrubs can improve slope stability, reducing the risk of shallow failures once roots have permeated soil to enhance cohesion. However, establishment of vegetation is hindered by poor soil fertility, frequently a characteristic of disturbed soils used in engineering projects. We evaluated whether compost could improve the rate of vegetation establishment and hence soil mechanical reinforcement by plant roots and therefore protect against shallow failures. Over 1200t of material was formed into a slope 40m long×15m wide, with an experimental soil slope angle of 20°. Washings from recycled mineral fill were used for the surface soil. Five amendment treatments were replicated three times in strips of 1.5m by 8m in a randomised block design on this slope; treatments were a no compost control, standard compost addition at a rate of 35tha-1 and a high level compost amendment at 300tha-1, applied either to the surface or incorporated into the topsoil to 10cm.Thirteen weeks after planting an amenity grass mix, vegetation cover increased up to 6 times compared to the control for 35tha-1 surface applied compost and similarly 20 times for 300tha-1 compost that had been surface applied. Root length density was about 3kmm-3 with no added compost and about 30kmm-3 for 300tha-1 added compost. At 35tha-1 compost, peak shear stress of the vegetated soil at 5cm depth was not affected, but it almost doubled with 300tha-1 compost compared to no amendment. Cohesion from plant roots was 8.1kPa for 300tha-1, in comparison to 2.1kPa for no amendment and 2.3kPa for 35tha-1 compost. Whereas surface application resulted in better vegetation cover, there were no differences in peak shear stress between plots with surface application or incorporation of compost. This study provided experimental evidence in the field that compost improvement to soil fertility has a positive impact on soil stabilisation by plant roots.

AB - Vegetation such as grasses and shrubs can improve slope stability, reducing the risk of shallow failures once roots have permeated soil to enhance cohesion. However, establishment of vegetation is hindered by poor soil fertility, frequently a characteristic of disturbed soils used in engineering projects. We evaluated whether compost could improve the rate of vegetation establishment and hence soil mechanical reinforcement by plant roots and therefore protect against shallow failures. Over 1200t of material was formed into a slope 40m long×15m wide, with an experimental soil slope angle of 20°. Washings from recycled mineral fill were used for the surface soil. Five amendment treatments were replicated three times in strips of 1.5m by 8m in a randomised block design on this slope; treatments were a no compost control, standard compost addition at a rate of 35tha-1 and a high level compost amendment at 300tha-1, applied either to the surface or incorporated into the topsoil to 10cm.Thirteen weeks after planting an amenity grass mix, vegetation cover increased up to 6 times compared to the control for 35tha-1 surface applied compost and similarly 20 times for 300tha-1 compost that had been surface applied. Root length density was about 3kmm-3 with no added compost and about 30kmm-3 for 300tha-1 added compost. At 35tha-1 compost, peak shear stress of the vegetated soil at 5cm depth was not affected, but it almost doubled with 300tha-1 compost compared to no amendment. Cohesion from plant roots was 8.1kPa for 300tha-1, in comparison to 2.1kPa for no amendment and 2.3kPa for 35tha-1 compost. Whereas surface application resulted in better vegetation cover, there were no differences in peak shear stress between plots with surface application or incorporation of compost. This study provided experimental evidence in the field that compost improvement to soil fertility has a positive impact on soil stabilisation by plant roots.

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Improved soil fertility from compost amendment increases root growth and reinforcement of surface soil on slopes

Abstract

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Keywords

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