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Maintenance of a healthy soil is fundamental to cereal and oilseed production. Structural stability is essential for maintaining quality and resilience of soil, which depends on the way the available physical, chemical, and biological elements in the soil interact. Good soil quality is essential for maximum productivity and profitability ensuring efficient nutrient recycling and minimal losses of nutrients, soil organic matter, pesticides and soil particles. Losses reduce the viability of land and pollute the environment.
Soil Biology and Fertility
Yield/Quality
Slumping and Capping
Waterlogging
Compaction
Wind Erosion
Water Erosion
Soil health depends on the presence of a varied and active population of micro-organisms. These both release nutrients from soil organic matter and chemical compounds but also as they break down soil OM and crop residues create gums which cement soil particles together and thus stabilise soil structures.
Physical soil quality is largely governed by soil organic matter (SOM) content, which is dynamic and responds to changes in soil management, and soil texture. A decline in SOM will affect soil structure and stability, water retention properties, buffering capacity, biological activity and the retention and exchange of nutrients. It may also in the medium and long term, make the soil more vulnerable to erosion, compaction, acidification, nutrient deficiency and drought.
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Crop rotations help increase yields overall, can build soil organic matter and improve soil fertility. An ideal crop rotation involves alternating cereals with legume, root crops, green manures, pulses and oilseeds. This produces differing amounts and types of residue (fragile vs. non-fragile) thus making crop residue and trash management easier. First wheat after break crops are the most consistent for yield and quality as they utilise multifunctional nutrient and crop protection contributions and provide many management solutions. Additionally, the different rooting characteristics of crops can affect soil condition and workability by providing a more stratified soil structure. This, in turn, supports a greater abundance and diversity of microorganisms, nematodes, earthworms and microarthropods, beneficial to plant productivity through their effects on soil formation, nutrient availability and biological control of pest organisms.
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A fine seedbed is unnecessary for cereals and oilseed establishment as problems may arise from too many passes. If too fine and low in soil organic matter surface capping can occur.
Soil capping reduces the ability of soils to absorb water falling on the surface leading to surface waterlogging and may also, in severe situations prevent the emergence of seedlings. Increasing SOM at the surface improves penetrability thereby, reducing capping and the risk of run-off of sediment, nutrients and pesticides.
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A good, loamy, permeable soil that is easily cultivated can suffer from water-logging in winter because it has a clay substrate, so it needs to be tended carefully. Below heavily compacted layers (35 - 45 cms depth) there is usually little evidence of either root or earthworm penetration
The impact on crop production would be two-fold, In wet years crops might suffer water-logging, because the water cannot drain efficiently. In dry years they might be drought stressed, because the plants simply will not have an effective, deep root system through which to draw up moisture from deeper in the soil profile.
Some earthworm species open up deep channels a metre down and more, which play a significant role in helping the soil's natural ability to drain.
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The use of increasingly larger and heavy machinery in cereal and oilseed cropping has increased the mechanical surface load exerted in fields. This creates stress on the soil reflected in compaction - the soils reaction to stress. Compaction of the topsoil horizon is created mainly by ground pressure and can be alleviated by wider /low pressure tyres. In ploughed fields a hard pan (10-20cm band) is frequently formed below the topsoil, at just below plough depth. This type of compaction is detrimental to infiltration and root growth and to the activity of those soil organisms that contribute to soil quality and are responsible for the soil formation processes.
Soil compaction is more persistent the deeper it gets and may require remedial actions every three or so years to minimize its impact on crop production. But the need for remedial action must be based on soil examination.
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Sandy and peaty soils are most prone to wind erosion.
Surface vegetation, trash and roots prevent the erosive action of wind. Overall wind erosion is not seen as a particular problem for combinable crops.
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Sandy, silty and low organic matter soils are vulnerable to water erosion. Bare soil in winter encourages water movement across soil surfaces and erosion can occur on any slope. Compacted soils are more prone as they prevent infiltration of rain. Surface and incorporated residues add stability to soil, aid infiltration and reduce the risk.
Water erosion has a strong economic impact on affected land and off-site on the surrounding civil and public infrastructure. Also, crop yields in eroded soils are lower than in protected soils as erosion reduces soil fertility and water availability. Leaching of nutrients and pesticides into surface and ground water causes eutrophication and poses a threat to aquatic organisms and impacts on drinking water quality. Loss of soil and agrochemicals is not only a source of pollution but is also a waste of valuable resource.
Off-site problems, caused by soil sediments transported in surface water from eroded agricultural land, may contribute damage to roadways and sewers, drainage disruption and siltation of harbours and channels, loss of reservoir storage, disruption of stream ecology and increased water treatment costs.
Most erosion events in the UK occur in winter cereal cropping (because these are the major crops) and are associated with tramlines, valley floor features and a lack of early ground cover. This not to say that the worst cases occur in winter cereal cropping
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HGCA Publications List
HGCA has a whole range of publications on its website that are free to view and download.
Links to relevant websites
Soil Management Initiative (SMI)
National Soil Resources Institute (NSRI)
The Allerton Trust
ADAS Conservation Advice
The Arable Group (TAG)
Scottish Agricultural College (SAC)
Natural England
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