Optimizing Plant Growth: the Power of Fertigation for Sustainability and Efficiency

Fertigation: a key to sustainable, efficient plant growth

Plants thrive when environmental factors are in balance. From absorbing CO2 in the air to accessing the right nutrients in the soil, each element plays a vital role in healthy plant development.

Fertigation management – fusion of irrigation and nutrient supply – is emerging as a crucial solution for achieving optimal plant nutrition. In the landscape of modern agriculture, Orius' Mixmaster exemplifies how technology can enhance biological processes to support sustainable and efficient plant growth.

What is needed for plants to grow?

Plants require several key environmental factors to grow and thrive.

Energy

Photosynthesis is a phenomenon that enables plants to produce glucose, which they use as a source of energy during their development. It takes place when plants absorb CO2 and water and receive light : CO2 and water serve as the raw materials for photosynthesis, while the quantity and intensity of light determine the speed of the process.

Water

Water plays various critical roles in plant physiology :

• Photosynthesis: as mentioned above, water is a raw material required for photosynthesis alongside CO2 and light.
• Thermal regulation: water helps to regulate the temperature of plant tissues.
• Structural support: water pressure within plant cells maintains their shape and rigidity.
• Nutrient Transport: water facilitates the transport of nutrients from the soil throughout the plant.

It's not just the quantity of water that counts, its quality plays a crucial role too. Factors like electrical conductivity (EC) and pH levels influence water's ability to supply nutrients to plant roots, affecting overall growth and vitality.

Nutrients

Like humans, plants need essential nutrients (macronutrients) : 

• Nitrogen (N) fuels plant growth and promotes the production of verdant foliage.
• Phosphorus (P) stimulates root development, flowering and fruiting.
• Potassium (K) facilitates the assimilation of nutrients and the circulation of sap within the plant.
• The role of Calcium (Ca) is twofold: it regulates nutrient transport and supports numerous enzymatic functions.
• Elements like Magnesium (Mg) or Sulfur (S) are important to the photosynthetic process.

In addition, oligoelements (micronutrients), such as Iron (Fe), Boron (B) and Manganese (Mn), are essential for various physiological processes ensuring optimal growth and metabolism.

The plant's root system captures and extracts nutrients from the soil only if they are in the form of ions dissolved in water.

Why fertigation is important for plants?

Fertigation ensures an optimum supply of water and nutrients, enabling plants to develop normally and healthily during their various growth phases (germination, flowering, etc.).

However, in certain environments, water from the soil and the air, as well as nutrients, can sometimes be limited or of poor quality. This limitation of resources can lead to water stress or nutritional deficiencies in plants, affecting their vitality and limiting their development. 

There are two types of deficiencies.

Simple deficiencies

Simple deficiencies resulting from a lack of nutrients, as shown in Figure 1, include :

• Potassium (K) deficiency : Wilted, burnt or stained leaves.
• Nitrogen (N) and Sulfur (S) deficiencies : Abnormal yellowing of leaves (Chlorosis).
• Phosphorus (P) deficiency : Darker, purplish leaves.
• Magnesium (Mg), Manganese (Mn) and Iron (Fe) deficiencies : Yellow discoloration of the tissues between the leaf veins, which remain green (Interveinal chlorosis).
• Boron (B) deficiency : Bud dieback. 

Induced deficiencies

Induced deficiencies result from an incorrect ratio of nutrients (e.g. excessive absorption of phosphorus, which limits the absorption of other compounds).

Modern agriculture's plant nutrition challenges 

Maintaining the fertility of the growing environment is essential to meet the nutritional needs of plants in the agricultural sector. In conventional farming, precise management of nutrient availability in the soil remains complex because it depends on many factors : 

• Biological activity : Microorganisms in the soil influence the decomposition of organic matter and the release of nutrients in a form that can be assimilated by plants.
• Soil composition : Texture, structure and mineral composition influence the soil's ability to retain nutrients and make them available to plants.
• Leaching phenomenon : The infiltration of water into the deep layers of the soil makes macro and micronutrients inaccessible to plants.
• Soil acidity : It affects the solubility of nutrients in soil water, and therefore their bioavailability to plants.

In response to this challenge, the use of fertilizers plays a crucial role in optimizing nutrient availability and supporting healthy plant growth.

Two types of fertilizer are commonly used :

• Organic fertilizers are derived from plant matter, animal excrement, wastewater and food waste. The nutrients contained in these fertilizers are rarely directly bioavailable, and must be broken down by animals, insects and microorganisms before being assimilated by plants.
• Inorganic fertilizers - Mineral fertilizers - can be produced from materials extracted from natural nutrient deposits or obtained by chemical synthesis. Mineral fertilizers contain nutrients that are directly bioavailable to plants.

Why must fertilizers be used with precision? 

Precision is vital for preventing pollution

Fertilizers must be applied in appropriate quantities to limit their impact on soil composition.

Indeed, even in ideal conditions a significant portion of fertilizers, whether organic or inorganic, is lost, modifying soil composition and increasing agricultural cost.

To give an example, plants use only 50% of nitrogenous fertilizers applied, due to the factors and phenomena presented in Figure 2. 

As a result, imprecise fertilization management can lead to pollution of soil and groundwater, mainly because of the nitrate levels they contain or produce.

This form of nitrogen is either produced over a period of time by soil microorganisms from organic fertilizers or contained directly in inorganic fertilizers. As previously mentioned, runoff and leaching transport nitrates through the soil until they reach groundwater. 

According to the French National Geological Service (BRGM), although nitrate levels in French groundwater have stabilized since 2004, it is still important to monitor them. As stipulated in the Groundwater Directive and the Drinking Water Directive, nitrate levels in groundwater must not exceed 50 mg/L in order to protect human health and water resources. Ingestion of these compounds can lead to the formation of nitrosated compounds, which promote the development of certain cancers. 

High nitrate levels in groundwater and surface water also affect aquatic ecosystems. They give rise to the phenomenon of eutrophication, characterized by a proliferation of algae caused by an overabundance of nutrients, leading to oxygen depletion and ecosystem imbalance (fish mortality, etc.). 

Other compounds from fertilizers, such as phosphates, pollute soil and groundwater, although to a lesser extent than nitrates.

Precision is essential for preserving resources

Another issue with fertilizers is that some of the resources required for their production - in particular inorganic fertilizers - are becoming increasingly scarce over the years. Phosphate rock reserves are limited, so it is crucial to ensure that extracted materials are widely used and recycled wherever possible.  

Precision is crucial for healthy plant development

Moreover, ensuring that plants receive the right nutrients, in the right quantities, at every stage of their development is another crucial aspect of agriculture. This remains a complex task in most agricultural systems, as plant needs change over time.

For instance, wheat crops absorb little nitrogen until tillering (beginning of new stem formation) and need a lot of this macronutrient between tillering and flowering, as shown in Figure 3.

In conventional agriculture, the use of organic fertilizers complicates the control of nutrient uptake by plants. As previously mentioned, plants can only absorb nutrients in the form of ionized compounds dissolved in water. Their nutrition therefore depends on the activity of specific soil bacteria, which mineralize the compounds present in organic fertilizers.

Determining the time required for microorganisms to transform these compounds into an assimilable form is extremely complicated. This process can take from a week to several months, depending on soil composition. Additionally, it is challenging to ascertain whether the compounds becomes bioavailable precisely when the plant needs them the most (see Figure 3).

Hydroponics as a solution? 

Hydroponic crops - soilless cultures in which nutrients are supplied via irrigation - offer solutions to the aforementioned challenges. There are several methods, among which the most famous are the following:

• Substrate cultivations where plants grow in a medium such as growfoam or sand, and receive a nutrient solution directly into their roots
• Aeroponics where plants are suspended in the air and are fed by a mist of nutrient solution sprayed directly onto their roots

These types of soilless cultivation enable an efficient use of resources (water, nutrients, fertilizers and cultivation area), but require strict, precise control of fertigation parameters.

This management is generally governed by dosing stations that deliver directly bioavailable nutrients to plants via the recirculating irrigation system: Injected nutrients that are not directly absorbed are returned to the reservoir and subsequently reused in the network.

This reduces the amount of resources needed to fertilize crops by 95-98%, making them fully profitable and more sustainable.

Furthermore these technologies enable quality parameters (pH and electro-conductivity) to be monitored using probes connected to the irrigation tank. This capability allows for the management of parameters that can affect nutrient uptake and thus plant vitality.

As previously mentioned, nutrient needs of plants vary as they grow. Consequently, adapting their nutrition at any given time remains a major challenge.

To address this need for precision and customization, Orius has developed the Mixmaster, an advanced fertigation system for recirculating hydroponics.

Mixmaster: Cutting-Edge Technology at the service of biology

The Mixmaster is an intelligent liquid fertilizer dosing system designed for closed-loop fertigation management.

Customization of nutrient recipes - managing the ratio of different elements added to the tank - is possible thanks to the Mixmaster and its numerous pumps and programmable injectors. In this way, in addition to the basic solutions injected into the irrigation solution (hydro A & B, pH up & down), additional elements can be introduced like silicate, H2O2 or micro and macronutrients, according to a predefined schedule. Moreover, the user can define a concentration target which the Mixmaster will take into account to automatically calculate injection volumes based on the actual tank level.

This precision management enables the adaptation of nutrition to the needs of the plant at its various stages of development, at any time, ensuring optimal crop growth. 

Not only is it adaptable to all plant needs, it is also compatible with all types of irrigation systems : The Mixmaster can effectively manage tanks ranging from 50 liters to over 10 m³ while maintaining a high dosing accuracy of 2%.

Finally, the Mixmaster is managed by BiomeOS. On the one hand, it acts as a control interface for managing all fertigation program parameters (injection recipes, etc.); on the other, it serves as a data platform with collecting (injection logs, historical time-series, etc.) and alerting capabilities. This interface provides precise control, even remotely, over all aspects of the fertigation process and a better understanding of plant needs.

Conclusion

Ensuring proper plant growth and development is a real challenge in all types of agriculture. By taking advantage of the Orius' Mixmaster, fertigation can be optimized to ensure plants have the right nutrition at different stages of growth.

However, nutrient management alone is not enough: Calcium, for example, is not directly assimilated by the plant. It is therefore necessary to play on other levers, such as climatic parameters (light, climate), to gain total control over plant growth. 

Would you like to know more? We will continue exploring the factors involved in plant growth in other upcoming articles.

Bibliographie

• Herencia JF, Ruiz-Porras JC, Melero S, Garcia-Galavis PA, Morillo E, Maqueda C. Comparison between Organic and Mineral Fertilization for Soil Fertility Levels, Crop Macronutrient Concentrations, and Yield. Agronomy Journal. 2007;99(4):973–83.
• Geisseler D. Nitrogen concentrations in harvested plant parts - A literature overview.
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• Wheat N Uptake [Internet]. [cited 2024 Jun 13].
• Directive - 2020/2184 - EN - EUR-Lex [Internet]. [cited 2024 Jun 18].
• Directive - 2006/118 - EN - EUR-Lex [Internet]. [cited 2024 Jun 18].