Soil aeration is among the primary conditions for plant development. However, while fertilization or irrigation is a regular practice for farmers, soil aeration importance is often underestimated and, therefore, remains unattended. Yet, beneficial soil aeration effects on root growth and activity ensure healthy vegetation and, consequently, high yields. Various soil aeration tools and methods allow maintaining proper air circulation in the subsurface, bringing vital oxygen to the root zone.
What Is Soil Aeration?
The process of soil aeration provides air supply underground by moving O2 and CO2 between the earth pores and the atmosphere. It helps avoid oxygen starvation in crops and reduce harmful carbon dioxide levels in the subsurface air if they rise too high.
What role does soil aeration play in root health?
Plant roots require atmospheric oxygen to respire and release energy for their needs from the glucose-oxygen reaction. In poorly aerated earths, roots are deprived of oxygen and fade because they can’t breathe properly. However, roots are essential to absorb nutrients and water, so the plant eventually dies. The impact of aeration on soil is not limited to crop growth. Soil aeration is necessary for aerobic earth-dwelling microorganisms and sufficient oxidation.
Causes Of Poor Soil Aeration
To ensure proper aeration of soil, it is critical to outline what affects it. Thus, farmers understand how to implement it and mitigate negative consequences. The factors affecting soil aeration include:
- soil moisture;
- soil texture;
- infiltration properties;
- machinery traffic;
- organic matter application;
- use for grazing, etc.
These factors may lead to soil compaction, excessive carbon dioxide content, and poor oxygen saturation.
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In most cases, poor soil aeration is caused by compaction. The finer the earth, the more prone it is to compaction. The smaller its particles, the more densely they attach to each other, leaving less space for oxygen. Denied oxygen, neither plants nor aerobic earth biota can survive. Compaction may be an adverse consequence of irrational irrigation and other field operations.
Irrespective of whether it is induced by natural forces or anthropogenic factors, waterlogging tampers with soil aeration. After downpours, floods, or excessive irrigation, water fills up the earth’s pore space, displacing the air and reducing the oxygen level nearly to zero. Roughly speaking, the air can’t penetrate the earth when the room is occupied with water. However, when it dries up again, the balance is restored. Water evaporates, and the air gets back to earth.
Soil Organic Matter
Organic matter boosts soil fertility. Nonetheless, the decomposition of organic matter involves a strong carbon dioxide release. Correspondingly, when organic matter content is too high, the production of CO2 may be too fast. Consequently, its removal slows down and may reach toxic levels. Another point is that carbon dioxide retention also interferes with oxygen supply, which the plant roots rely on and are supposed to get in the process of the earth and atmospheric air exchange. This is why it is necessary to add organic matter moderately or in an already decomposed state.
Grazing With Livestock
Grazing practices contribute to soil fertility with organic manure. However, trotting around the pasture, animals also cause soil compaction with their hoofs if they stay too long in the same area. In this regard, rotational pastures prove to be an efficient problem solution.
Regular Vehicular Traffic
Heavy machinery compresses farmlands, thus also leading to compaction. For this reason, the movement of massive field equipment like forage harvesters, manure spreaders, etc., should be limited, and treatment frequency wisely reduced. The situation gets even worse when the earth is wetStephen Davies, Derk Bakker, Jeremy Lemon. The science of soil compaction. Department of Primary Industries and Regional Development's Agriculture and Food division..
Due to compaction, plant roots can’t develop properly, which causes yield losses in the long run. The situation is critical when compaction combines with dry weather conditions. In this case, roots not only can’t breathe but can’t absorb water and nutrients as well. On the contrary, when compaction combines with wet weather conditions, it hampers grazing and promotes soil erosion with fast liquid runoffs.
Soil Aeration Methods
The aim of soil aeration is to supply oxygen to the topsoil to make it available for crop roots and earth microorganisms. Aeration also makes the topsoil softer and improves its infiltration properties. It is carried out with a number of methods, each of which depends on the area scope and land specifics.
Actually, the radical approach suggests removing the land cover and restarting it. However, it is not always feasible, to say nothing of the costs and efforts applied. Aeration of soil is a far better solution. In this case, its standard techniques include spike, plug (core), and liquid aeration.
The spike aeration method produces the least land disturbance by making holes for the air to penetrate. However, it embraces a relatively small area due to limited coverage of applicable tools, which include soil aeration shoes, prongs, rollers, and mower attachments. They all contain spikes for earth piercing. The first three options imply walking or manual operations, by pushing or rolling. On the one hand, they are the least sophisticated. On the other hand, they require considerable physical strength. Mower attachments demand less human efforts since they are adjusted to machinery.
Note: Such a technique is perfect for sandy soils. It is not suitable for clay ones though, because they take the spike shape, which results in compaction.
The core soil aeration method addresses “cores” or “plugs”, which is especially relevant for compacted clay soils. Cores consist of clay, roots, thatch, etc., in the topsoil layer. Unlike the previous method, it suggests not piercing the earth but pulling its parts out, leaving them on the surface.
Core aeration makes the field somewhat messy yet has certain advantages. The benefits of soil core aeration comprise:
- enhanced gaseous exchange;
- intensified oxygen saturation to the root zone;
- raised water infiltration;
- improved earth structure;
- incorporated organic matter.
Core-removing soil aeration equipment includes manual aerators and mower attachments.
The previous methods work with the soil directly, but liquid applications contribute to aeration differently. Liquid aerators consist of a wetting agent and nourishment for earth-dwelling biota.
Wetting agents improve infiltration, and water reaches deeper levels of the soil profile. It enables microorganisms to dig deeper, too. By digging, they improve soil aeration and allow water to seep even lower as well, which boosts root development.
Furthermore, liquid aerators contain food for bacteria (mainly seaweed extract) to boost their activity. In its turn, this is beneficial for worms that move underground adding to earth porosity. It helps air and water penetrate farther through the prepared “ways”. Besides, worms and insects process organic matter, boosting soil fertility.
Soil aeration methods work better in combination. For example, it is useful to apply liquid aerators a week before core removals.
Why Tillage Is Not The Best Option For Aeration
Tilling is the most intensive earth disturbance that implies digging, turning it upside down, and breaking huge parts into smaller pieces. Obviously, tilling operations reduce compaction and enhance oxygen supply, but they are helpful in the short run only. The adverse effects of heavy earth disturbance make its repeated implementation a dubious and unjustified practice:
- disrupted soil health due to risks of wind and water erosion;
- destroyed beneficial microorganisms (however, tillage also impacts pests and their larvae as part of integrated pest control);
- uncovered weed seeds from the subsurface layers (yet, at the same time, tillage places the seeds from the surface underground and destroys weeds, being a mechanical method of integrated weed management);
- polluted atmosphere with fossil fuel emissions from tilling machinery (which contributes to climate change).
Researches reveal that tillage is among the positive factors affecting soil aeration. In particular, a study estimated the impact of tillage on oxygen diffusion rate (ODR) in the production of peanut crops on lateritic sandy loam earths. The scientists applied five tillage techniques (mouldboard, rotary tiller, cultivator, wedge, and no-tilling), and mouldboard tillage showed the highest ODR rateA. R. Khan. Influence Of Tillage On Soil Aeration. Journal of Agronomy and Crop Science. Volume 177, Issue 4. https://doi.org/10.1111/j.1439-037X.1996.tb00243.x. However, the difference in values smoothed in deeper earth layers and with plant development progression. So, tillage is efficient only in the short-term perspective. Besides, it may subject lands to erosion, which is a significant advert consequence.
Assistance Of EOSDA Crop Monitoring
Although one cannot observe poor soil aeration directly, it will definitely impact field productivity. The EOSDA Crop Monitoring zoning feature allows farmers to track it by generating productivity maps. Growers can also compare them in the long run to understand if the crops are still healthy. If they are not, it may be due to a lack of required nutrients and favorable soil structure. Then, they can assign scouting tasks through the EOSDA Crop Monitoring app to inspect the situation properly. It is ultimately beneficial for farmers who practice no-till. It is crucial for clay farmland owners, as this soil type is highly prone to compaction. They can monitor the crop state and outline different field zones depending on vegetation levels. This way they will be able to estimate their field’s productivity.
Note about clay soils: Typically, soil includes clay, sand, and silt as its main components. Clay is perfect to retain nutrients and moisture. However, due to small pore spaces, it absorbs water slowly, so it requires moderate irrigation. Soil aeration is particularly beneficial for clay fields, improving porosity and water absorption.
Also, as decreased soil aeration depends on the moisture level in the ground, it is necessary to maintain the optimal moisture content. EOSDA Crop Monitoring enables farmers to track moisture in the root zone and surface zone (5-cm topsoil). The product displays the analytics of the selected period with several consequent curves and other data:
- vegetation index of your interest (NDVI, NDRE, MSAVI, ReCl) or moisture index NDMI;
- root-zone and surface moisture;
- stages of plant growth;
The NDMI index tracks the moisture content in the plants themselves. A high level of moisture can indicate that the earth is over-irrigated that can lead to waterlogging. As mentioned above, in its turn, waterlogging is among the causes of poor aeration. So, too high values of NDMI alarm farmers that crops are experiencing some problems in their development.
Why Is Soil Aeration Important?
The availability of nutrients for crops immediately relates to the degree of soil aeration. Well-aerated soils provide more favorable growth conditions, while nutrient imbalance and poor aeration impede plant development.
The impact of soil aeration on nutrient supply is as follows:
- Nitrogen. Organic nitrogen fixation and mineralization are carried out with nitrogen-fixing plants (especially legumes), organic matter, and livestock wastes. Organic nitrogen is reduced to plant-digestible forms by aerobic bacteria that can function properly only under sufficient soil aeration. Poor aeration induces a split of nitrates to nitrous oxide (N2O), which is among the potent gases contributing to the greenhouse effect. Besides, denitrifying bacteria are more likely to deprive crops of nitrates in poor earths. This happens because most denitrifying bacteria are facultative aerobic. It means that when O2 is available, they will use it (aerobic respiration). When the O2 level is poor, they will switch to NO3 or NO2 (anaerobic respiration).
- Manganese and iron have high valence in well-aerated soils and low valence in poorly-aerated ones. Although plants can consume only low-valency forms, their excessive absorption is harmful to crops. For this reason, excessive access to low-valency forms must be limited, and toxicity risks are mitigated with aeration.
- Sulfur is represented by sulfate in aerated soils, which is suitable for plants. Sulfate turns into sulfide under poor aeration (waterlogging), and hydrogen sulfide is harmful to crops, too.
Nutrient imbalance results in the deviance of root formation, which will inevitably affect the whole plant and cause yield losses. Signs of poor aeration include thick, short, dark roots of abnormal shapes, poorly developed hairs, etc.
Another important disadvantage of insufficient aeration is higher crop susceptibility to pathogens and root-rotting fungi, in particular. Correspondingly, aeration becomes an effective prevention technique, decreasing crop and tree disease risks.
The aforementioned factors reveal different perspectives of soil aeration importance. Understanding its necessity and proper implementation time is easier with online farming tools. Request a demo and see what you can do with EOSDA Crop Monitoring in your fields.
Vasyl Cherlinka has over 30 years of experience in agronomy and pedology (soil science). He is a Doctor of Biosciences with a specialization in soil science.
Dr. Cherlinka attended the engineering college in Ukraine (1989-1993), went on to deepen his expertise in agrochemistry and agronomy in the Chernivtsi National University in the specialty, “Agrochemistry and soil science”.
In 2001, he successfully defended a thesis, “Substantiation of Agroecological Conformity of Models of Soil Fertility and its Factors to the Requirements of Field Cultures” and obtained the degree of Biosciences Candidate with a special emphasis on soil science from the NSC “Institute for Soil Science and Agrochemistry Research named after O.N. Sokolovsky”.
In 2019, Dr. Cherlinka successfully defended a thesis, “Digital Elevation Models in Soil Science: Theoretical and Methodological Foundations and Practical Use” and obtained the Sc.D. in Biosciences with a specialization in soil science.
Vasyl is married, has two children (son and daughter). He has a lifelong passion for sports (he’s a candidate for Master of Sports of Ukraine in powerlifting and has even taken part in Strongman competitions).
Since 2018, Dr. Cherlinka has been advising EOSDA on problems in soil science, agronomy, and agrochemistry.
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