In the world of hydroponics, there are many hidden and niche techniques which were drawn from soil cultivation principles which have proven ultimately effective. Can the oldest cultivation technique of crop rotation find application in hydroponics or do we forget about it?
Crop rotation has no application in hydroponics because of the possibility to quickly and more efficiently improve the nutrient levels in the hydroponic growing medium. In hydroponics, nutrient imbalance problems are solved by adjusting the nutrients in the reservoir and not by regularly alternating plants in precise cycles.
However, despite its lack of applicability in hydroponics, the fundamentals of the practice have some similarities to hydroponics, namely the nutritional content and the presence of microorganisms. A keen understanding of hydroponics requires a keen understanding of traditional soil cultivation as well!
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Crop rotation is a well-known soil cultivation practice that consists in planting different series of crops in a plot of land per growing season. This is proven able to improve soil health and harvest.
The theory of crop rotation is that alternating between crops will improve soil quality and nutrients since different plants consume different nutrient sets as well as their (different) decaying organic matter will provide the soil with different type nutrients as well.
Additionally, increasing the biodiversity in a plot of arable land improves soil organic matter, nitrogen content, weed management, pest and pathogen control.
Crop rotation is not applicable in hydroponics because nutrient balance in hydroponics is achieved by observing and adjusting the nutrient-rich solution in the reservoir, and not by alternating the growing plants per cycle.
Any imbalance can be adjusted by incorporating ready-made nutrient solutions or specific chemical nutrients into the hydroponic nutrient reservoir. This is also the case with non-essential nutrients such as silica, not commonly available in regular soil.
The key difference is that in crop rotation, the nutrient level into the soil (the growing medium) is improved by changing the plants. In hydroponics, this is not necessary and is actually the reverse. In hydroponics, plants are not needed to change the nutrients levels.
To illustrate, crop rotation is done by alternating from soybeans to maize to improve the quality of the soil and the plants. For this set up, a study has shown a yield increase by 5-20%.
In hydroponics, when the nutrient reservoir has been depleted, nutrients can be added in again to sustain and improve plant growth. Studies have shown increased yield and growth rate depending on the plant.
Given the difference between soil and soilless cultivation, it is apparent that there are some things that may be found in soil but not present in hydroponics, and vice versa.
Whatever nutrients found in soil can be easily added into an hydroponic system if missing.
As previously stated, any nutrient deficiency can be incorporated into the system through the use of ready-made nutrient solutions or chemicals which can be purchased separately. Likewise nutrients not necessary but beneficial to plant growth can also be easily incorporated into the system.
Microorganisms are both present in soil and hydroponics.
However, given the controlled conditions in hydroponics, the presence of harmful microorganisms (certain bacteria, fungi, viruses, and oomycetes) are less common than in soil. Hydroponic systems are aimed to be sterile and clean which prevents the proliferation of these harmful organisms.
Beneficial microorganisms (i.e Bacillus spp., Pythium spp., Pseudomonas spp., Fusarium spp., and Lysobacter spp, among others) are present in both soil and hydroponics. Nonetheless, they tend to be even more beneficial in hydroponics because of the lack of competition with harmful microorganisms.
Weeds, insects, fungi, microorganisms, and other harmful animals are more present in soil than they are in hydroponics. As stated before, hydroponics is commonly sterile. A clean environment lends itself to a growing condition free from pests.
Given the lack of soil and the need for crop rotation in hydroponics, why is growing medium composed of soil or other similar materials still used in hydroponics?
The purpose of growing mediums are three-fold: (1) physical support, (2) nutrient retention, and (3) water retention.
It provides physical support for seeds so that they will not slip and fall from the net pot’s slits. For growing plants, the growing medium allows them to grow upright and hold some part of the root system.
As for nutrient and water retention, growing mediums can retain some nutrients and moisture which may act as a good substrate for seedling or a buffer for grown plants. This is especially useful when a grower becomes negligent and forgets to change-out the nutrient reservoir or re-add nutrients.
For a more informative look into growing mediums, we have an informative list of alternatives to the most common growing medium, rockwool.
- Crop rotation is an effective soil practice in improving plant growth and soil health.
- Crop rotation is not applicable in hydroponics because the nutrient medium is adjusted for any deficiency in nutrients.
- The only application of soil in hydroponics is as a growing medium for net pots. The purpose is to provide a substrate for seeds or physical support for the plant system.
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