By Karla Garcia and Deidre Hughes
Root zone environment is directly related to our crop growth, development and health. Therefore it is very important to understand what is going on underneath our plants.
There are three primary aspects of our rootzone environment:
- Nutrient content
- Electrical conductivity
Nutrient content is a key factor in crop production. Based on crop nutrition plants are able to stay vegetative, bloom or produce fruit. We can control their health by avoiding any nutrient deficiency or toxicity. Basically by understanding plant nutrition you will have one of the most powerful tools in crop production. Most required nutrients in plants are called “Macronutrients”. These nutrients are essential and required in high quantities. Primary macronutrients are N (nitrogen), P (phosphorus) and K (potassium). Secondary macronutrients are Ca (calcium), Mg (magnesium) and S (sulfur). The rest of essential nutrients in plant nutrition are called “micronutrients”: Fe (iron), Mn (manganese), Zn (zinc), Cu (copper), B (boron), Mo (molybdenum), Ni (nickel), Cl (chloride). Micronutrients are mostly involved in enzyme function and are required in smaller amounts. Si (Silicon) is another element that is not essential but may improve the health of your plant. Si is commonly found in soil and can aid in plant structure and strength creating some resistance to environmental stresses.
Our first concern as growers should be to provide all essential nutrients for plant health. But is that all? Unfortunately, nutrients alone will not maintain our plant health. We need to create an ideal environment at the root zone for our plants to grow happy and healthy. First we need to understand plants can uptake nutrients via different pathways: Ion diffusion, mass flow of water and selective ion absorption. Mass flow is mainly used in Ca and Mg uptake. This would be considered passive uptake. By recognizing how nutrients transport, then we can apply the correct approach to create all ideal conditions to promote plant nutrient uptake. For more information on plant nutrition click here. Some nutrients like N, P and K have a high mobility from old to new tissue meaning deficiency symptoms will first take place and often be visible in older leaves. It is important to identify your crop’s needs and understand that your crop can have different nutrition requirements depending on species, growth stages and nutrient delivery methods.
Once we have an understanding of the nutritional content provided at rootzone level, we next need to pay attention to pH and EC (electrical conductivity). In order to provide the ideal conditions for nutrient uptake we need to make sure pH and EC levels are accurate for our crop.
Electrical conductivity or EC provides information on the general fertility level of the nutrient solution and gives you information about salinity levels. The unit used to measure EC is dS m-1. The higher the salt levels, the higher the EC reading. A typical hydroponic solution can have EC between 1 and 3 dS m-1. But for ideal ranges consult your crop specific requirements. Usually different EC levels (from low to high) are used in fruiting crops like tomato or cucumber during different growth stages. Other crops such as strawberries demand low EC levels (1 dS m-1) during the whole cycle. Excessive fertilizer use can decrease uptake of water so be careful to not let your EC drift upward as your water reservoir lowers. Keeping the water topped off consistently can be helpful in avoiding this. Also, take note as the ambient temperature rises in your growing area, your plant will likely take up more water and can get the needed nutrition with a slightly lower EC.
You should be aware that pH affects forms of available ions, the solubility of salts and ion uptake. Therefore pH should always be monitored and kept in acceptable ranges in order to avoid nutrient deficiencies. Try to avoid pH swings- consistency is key. One whole number increase or decrease in pH (ex. 6.0 to 7.0) is actually ten times either more acidic or more alkaline depending on which direction the number moves.
Other aspects should also be considered to provide optimum root zone environment: The growing media for example. The chemical composition, cation exchange capacity (CEC), moisture content and volume of your growing media can also affect nutrient uptake. You should always consider quality when choosing your growing media. In most cases, good media should provide low CEC, high pH buffering capacity and good porosity. Porosity is a crop specific requirement.
Last, but not any less important, are environmental conditions. This includes temperature (root zone and air), solar radiation, airflow and water availability which can also have an impact on nutrient uptake.
Remember to always keep an eye on the rootzone environment of your crop. Hort Americas offers practical solutions for rootzone monitoring within all budgets. We offer sensors, growing media, fertilizers and more. Please browse our website to check out our products or contact us if there is something you’re looking for that isn’t listed. And as always, we’re here to provide technical support to growers like you. Happy growing!