Soil structure and pasture quality


Soil formation is a long and multifactorial process that consists of rock breakdown and organic decomposition.

The rock, also called parent material, is broken down through weathering, which can be physical, chemical or biological (Queensland Government, 2013).

Soil formation is affected by :

  • the parent material creating the mineral basis of the soil and affecting soil properties,
  • its living organisms affecting weathering and organic matter,
  • the climate affecting weathering as rainfalls dissolve some parent material and hold others in suspension,
  • frost as ice breaks rocks

Also, organic decomposition is faster in humid, and warmer weather. The topography affects deposition and erosion, as with slope, drainage is increased, limiting the effect of rainfalls, modifying the type of vegetation, and limiting depositions : shallower soils on hills as depositions will sink, deeper and more fertile soils in valleys as they will benefit from depositions (alluvial, colluvial or aeolian), and time affecting soil properties as it plays into weathering and organic deposition (Queensland Government, 2013).

Soil horizons are the layers of different matter that can be found in a cross-section of the ground. Those different layers, forming the soil’s profile, are often composed of a surface horizon composed of plant litter, under which is an horizon composed of humus top-soil, with a high organic composition and nutrient availability, hosting a high biological activity. Then a sub-soil composed of clay or sand, resulting from the weathering of the parent material. And the deeper horizon, composed of weathered rocks (Queensland Government, 2013).

Soil classification is then made from these profiles, to sort soils from their composition (loam, sand, silt) (Minnesota pollution control agency, 2023). The classification is later used, in correlation with relief maps to create soil maps (Minasny et al., 2014).


Soil texture is determined by the mineral composition of a soil sample. Soil texture is defined by the amount of sand, clay and loam within the soil, the amount of each component can add to make different types of soil textures (Queensland Government, 2013).

Soil texture determines the fertility and water holding capacity of the soil. Also, depending on the soil profile, different soil textures can be found, uniform, texture contrasted or gradational (Queensland Government, 2013).

Soil texture can be determined by various protocols. « Homemade » protocols include the jar method which is quite accurate, and consists of filling 1 ⁄ 3 of a jar with soil cleaned of any debris, rocks or large organic matter, adding water up to 1 cm from the top, adding a tablespoon of dishwashing detergent and shaking the jar. After setting the jar on an even surface, after one minute, the sand part of the sample will be settled at the bottom, followed by silt after 2 hours and clay after 48 hours, leaving clear water once all the deposits have been made. Then we can measure the height of each component and calculate the percentage of each component within the sample, giving the soil texture of the sample (Jeffers, 2022).

Or a lab test of the sample with more advanced protocols can also give a more accurate result.


Soil structure reflects the way components of the soil texture (sand, clay, silt) are arranged together to form aggregates (Queensland Government, 2013).

Soil structure will impact the way water and air can move and drain within the soil. Poor soil structure will lead to poor fertility, drainage and stability of the soil. Also, soil with bad structure can lead to runoff and can be so compacted that it is impossible for plants to form early roots and survive (Swarmhub, 2017).

Soil structure can deteriorate with compaction, excessive sodium, removal of vegetation, cultivation, screening or excessive moving or handling of soil (Shanstrom, 2023).

Improving soil structure can be done by avoiding working on wet soils to avoid compaction, reducing unnecessary trips across the field, reduce tillage and equipment weight, rotate crops or use rotational grazing to avoid compacting and depleting the soil of its nutrients, increasing the amount of organic matter within the topsoil, planting cover crops and deep rooting plants such as annual ryegrass or clover (Farm Progress, 2023). Adding sand to clay soils can also help improve clay soil structure.

Also ploughing can help improve soil structure by breaking up the soil surface and providing a great seedbed, however, excessive ploughing can have the opposite effect and destroy soil structure… This is why ploughing can be good when reseeding a new pasture (Farrington Oils, 2019), then harrowing can be done, after spreading composted manure or another organic matter to help aerate the soil and mix the organic matter within the topsoil.

Each soil texture can have a specific, more precise way to help improve its structure, what remains true for each and every soil is to avoid working on wet soils to avoid compaction and to increase the soil’s organic matter are great ways to improve soil’s structure.


Depending on the soil type and texture, different grass species will be able to thrive (or not) in the soil.

For example, sandy soils will do better welcoming grasses as fescues (fine fescue, sheep fescue, turf-type tail fescue) or bermudagrass, zoysia or bahiagrass, as they are more tolerant to sandy soils thanks to their deep roots and lower need for water (Christensen, 2022).

Clay soils are problematic as they tend to be really compact and thus hard for plants to set roots in. Grasses as tall fescue or buffalograss will be able to set in clay soils (Christensen, 2022).

Silt soils would be the best ones to work with as they drain well, but still retain enough moisture and tend to have a good fertility and can be suitable for most grasses (Christensen, 2022).

Management of soil also makes a big difference on the development of the sward.

Improving soil texture by adding organic matter to the soil and aerating it helps grasses to thrive and grow. Also, avoiding working on wet soils helps limit compaction (Christensen, 2022).

Rotational grazing can offer a break to the pasture for regeneration and thus help grasses settle deeper in the soil and be more resistant to drought or grazing.

Knowing the composition of your soil is the key to maximising productivity:

    • Sow the right forage species, which will thrive and help maintain the soil,
    • Install suitable drainage to avoid damaging the soil structure and "drowning" the grass, 
    • Improve the structure by various works or additions of material, 
    • Opt for rotational grazing to avoid saturating the meadows and help them regenerate



Christensen, S. (2022) The dirty truth: How different soil types influence your lawn grass, Nature’s Seed. Available at: (Accessed: 20 June 2023). 

Farm Progress (2023) 10 ways you can improve soil structure, Farm Progress. Available at: (Accessed: 19 June 2023). 

Farrington Oils (2019) Why we no longer plough our fields…, Farrington Oils. Available at:,for%20plants%20to%20grow%20in. (Accessed: 19 June 2023). 

Jeffers, A. (2022) Soil Texture Analysis ‘The jar test’, Home & Garden Information Center | Clemson University, South Carolina. Available at:,to%20determine%20the%20soil%20type. (Accessed: 19 June 2023). 

Minasny, B. et al. (2014) ‘Pedometrics’, Reference Module in Earth Systems and Environmental Sciences [Preprint]. doi:10.1016/b978-0-12-409548-9.09163-6. 

Minnesota pollution control agency (2023) Soil Classification Soil Classification, Soil classification – Minnesota Stormwater Manual. Available at:,and%20clay%20in%20a%20soil. (Accessed: 19 June 2023). 

Queensland Government (2013a) How soils form, Queensland Government. Available at:,help%20break%20down%20parent%20material. (Accessed: 19 June 2023). 

Queensland Government (2013b) Soil structure, Queensland Government. Available at:,crumbs%20through%20to%20large%20blocks.&text=Some%20soils%20resemble%20a%20large,have%20little%20or%20no%20structure. (Accessed: 19 June 2023). 

Queensland Government (2013c) Soil texture, Queensland Government. Available at:,made%20up%20largely%20of%20clay. (Accessed: 19 June 2023). 

Shanstrom, N. (2023) What is soil structure and why is it important?, Deeproot. Available at: (Accessed: 19 June 2023). 

Swarmhub (2017) Soil structure, Swarmhub. Available at: (Accessed: 19 June 2023).


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