Agricultural Management Techniques (AMTs) are crucial to soil quality because crop growth is reliant on stable, nutrition-rich, porous, biodiverse soil.
Conventional methods of industrialized modern farming can lead to the quality of soil deteriorating to the extent that crop yields significantly suffer, which can undermine sustainable farming endeavors. However, alternative AMTs for tillage, planting, fertilization, and irrigation can be adopted which maintain, enhance and restore soil quality.
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Heavily mechanized harrowing, digging, rototilling, and turning over of the soil are conventionally adopted methods of preparing agricultural land for planting, but they can adversely affect soil quality by increasing the problem of soil compaction.
Crops struggle to flourish in compacted soil because water, nutrients, and air vital to their growth find it much more difficult to travel through dense compacted soil structures. Alternative AMTs for tilling, such as minimal tillage or no-tillage can improve soil quality by enabling a healthy through-flow of nutrients, water, and air for roots to absorb, and for plants to thrive.
Monoculture systems of crop planting can reduce soil quality by making it less nutritious for crops. AMTs which include a diverse selection of plants and other wildlife enable the soil to develop and contain a variety of microorganisms (eg fungi and bacteria) that break down decaying organic matter and release nutrients. Specialized agricultural soil contains much fewer of these microorganisms, which means crops have access to fewer nutrients in the soil.
Planting permanent cover crops, rather than leaving the soil exposed to the elements is another AMT which not only aids biodiversity, and thereby increased nutrients in the soil, but also helps improve soil aggregate stability and reduces the risk of erosion.
Natural vegetation provides an effective defense against soil degradation leading to the desertification of Mediterranean land (Garcia et al, 2012), for example, and cover crops further enhance the biodiversity of the land, which in turn aids with pest and disease management, as well as weed control.
Agroforestry - the practice of planting trees, hedges, and other woody perennials on agricultural land - can also enhance the climate resilience of the soil by providing some protection against extreme temperatures, high wind speeds, and the excessive rainfall or drought characteristic of unpredictable weather patterns.
The planting of leguminous crops (pulses) alongside other crops as an AMT, has been found to have multiple benefits to the soil. These include enabling soil pH to reach an optimal level for crop-growing (ideally between 6 and 7), improved soil structure, reduced soil degradation, increased nutrient recycling and porosity, and reduced risk of diseases and weeds (Alaoui et al, 2020).
Crop rotation rather than specialized agriculture enhances soil health not only because of the numerous biodiversity benefits it provides but because of the increase in soil organic matter (SOM). The greater the SOM, the greater the potential for water infiltration and nutrient uptake (as opposed to leaching) as well as carbon sequestration. SOM also reduces the likelihood of surface crusting and soil compaction.
Excessive use of synthetic fertilizers is hazardous to the environment, as well as the agroecosystem and the crops attempting to thrive in it. They destroy microorganisms in the soil which are vital for nutrient recycling and increase water pollution, as the nitrogen and phosphate they contain leaches into groundwater, creating toxicity. Polluted water from agricultural land then flows into lakes, rivers, and streams, leading to the wider ecosystem becoming toxified.
Alternative AMTs such as the use of green manure/crop residue, mulching, animal manure, and composting may be slower to be absorbed by plants than synthetic fertilizers, but they provide a much more sustainable method of fertilization in the long term without the disadvantages of degrading the soil and polluting the environment, which adversely affects crop yield.
Fertilizers that raise the pH of the soil to make it either too alkali (above 7) or too acidic (below 6/7) are to be avoided if soil health is to be maintained, therefore consideration of the most suitable fertilizers to use in terms of nitrogen, phosphate and potassium levels is crucial.
Water uptake by crops is essential for growth, and their roots need to be able to absorb water through the soil. Therefore soil needs to be able to both retain sufficient water for absorption and to drain effectively to avoid waterlogging. Ideally, the soil should have pore spaces of various sizes between particles, rather than being compact, so that good transport of water and air is achieved.
Rainfall, whether climate change-induced excessive rainfall or otherwise, can exacerbate leaching in poor quality soils. This means that crops not only receive insufficient water uptake but also that the soil can become too acidic, as minerals such as sodium, magnesium, potassium, and calcium drain out of the soil before being absorbed by the plants’ roots.
Incorporating vegetation through crop cover and woody perennials is a natural way to improve the porosity, retention, and drainage of water in the soil. The use of smart irrigation systems, drip irrigation, rainwater harvesting, and other prudent water management AMTs can promote a timely and sufficient supply of water to crops, which is especially important in regions where water availability may be unpredictable or scarce.
Which AMTs are most beneficial for soil quality?
A study that used a visual tool assessment of soil quality to identify the effectiveness of alternative AMTs on 138 pairs of farm plots across 14 sites in Europe and China identified that the AMTs most beneficial to soil health were no-tillage, crop rotation, composting and manuring, when used singly.
When alternative AMTs were used in combination, the study showed that minimum tillage, crop rotation, and mulching were the most advantageous to soil quality. (Alaoui et al, 2020).
AMTs significantly affect soil quality, therefore sustainability-conscious decisions about which ones to adopt can help optimize soil quality, and in turn, crop yield.
- García-Orenes, F.; Roldán, A.; Mataix-Solera, J.; Cerda, A.; Campoy, M.; Arcenegui, V.; Caravaca, F. (2012) Soil structural stability and erosion rates influenced by agricultural management practices in a semi-arid Mediterranean agro-ecosystem. Soil Use and Management, December 2012, 28, 571–579. https://doi.org/10.1111/j.1475-2743.2012.00451.x
- Alaoui, A.; Barão, L.; Ferreira, C.S.S.; Schwilch, G.; Basch, G.; Garcia-Orenes, F.; Morugan, A.; Mataix-Solera, J.; Kosmas, C.; Glavan, M.; Szabó, B.; Hermann, T.; Vizitiu, O.P.; Lipiec, J.; Frąc, M.; Reintam, E.; Xu, M.; Di, J.; Fan, Z.; Sukkel, W.; Lemesle, J.; Geissen, V.; Fleskens. L.; (2020) Visual assessment of the impact of agricultural management practices on soil quality. Agronomy Journal, 2020;112:2608–2623. Wiley Periodicals, Inc. on behalf of American Society of Agronomy. DOI: 10.1002/agj2.20216