This is part 2 of a 4-part series on a guaranteed analysis of organic hydroponic nutrient products. Part 1 can be found here.
Water Soluble vs Water Insoluble Macronutrients
Any fertilizer that dissolves in water is considered to be “water soluble”. Why is this important to know? Well, it’s because solubility impacts how easy it is for a plant to absorb nutrients. The nutrients must be able to move through the plant from its roots to its stem and leaves, ultimately reaching its cells, driving critical functions such as the production of chlorophyll.
Typically, a dry or granulated fertilizer’s maximum solubility is listed on its packaging label, indicating the maximum pounds of fertilizer that can be dissolved in a gallon of water.
It’s critical that a farm understands that the solubility or “absorption” of all minerals (macro and micronutrients) is impacted by the grow media’s pH level.
Believe it or not, we’ve experienced first-hand growing buttercrisp lettuce in severely alkaline water, reaching levels in the range of 7.5-8.2. We were still able to grow the lettuce successfully but at a significantly lower growth rate without nutrient deficiencies (as shown below). Interestingly enough, we were still able to achieve this growth with an NPK of less than 1% for Nitrogen, Phosphorus, and Potassium, and sourced solely from mixed vegetative byproducts. We should note that this was an early trial of ours which was performed three years ago. During this time however, we did encounter biofilm, which was a function of not having processed the vegetative byproducts. Now, through our Organic Cycling Science™ approach that we implement throughout the entire development of our organic hydroponic nutrients, this is no longer an issue that we face. Admittedly, the alkaline water certainly made it difficult for minerals such as Iron, Calcium, Magnesium, and Phosphorus to be absorbed by the plants roots. However, it did aid in mineralizing the nutrients due to its source.
"Interestingly enough, we were still able to achieve this growth with an NPK of less than 1% for Nitrogen, Phosphorus, and Potassium, and sourced solely from mixed vegetative byproducts."
Left: DWC trial using Re-Nuble's Organic Hydroponic Nutrients
Right: DWC trial using Synthetic Mineral Salts
Typically, a pH range of 6.0, 7.2, and in some cases, 7.5 is acceptable for most plants. It is helpful to check the pH of a farm’s source water as different plants thrive in different pH ranges. pH can determine optimum plant growth and should be monitored closely. Understanding the pH of not only a farm’s grow media but also its source nutrients as varying inputs will impact not only the initial pH but the potential for a pH that may fluctuate due to the decomposition of biological inputs.
By now you’re probably wondering, “Okay, so how will this impact my decision when deciding to purchase organic nutrients vs synthetic mineral salts for my farm?”. For the most part, raw organic fertilizers are not available as water-soluble macronutrients. They are often bound in carbon and/or proteins that require additional decomposition or mineralization in order for them to become available to the plant. This is where we get really excited because this is the piece of the puzzle that Re-Nuble has solved.
"For the most part, raw organic fertilizers are not available as water-soluble macronutrients... This is where we get really excited because this is the piece of the puzzle that Re-Nuble has solved."
Understanding How Plants Use Water Soluble Nitrogen Fertilizers
For water soluble fertilizers, farms can easily control the precision of nutrients inputted into a farming system. Using a water soluble nitrogen fertilizer, one of the most important nutrients, is important because nitrogen is used to make proteins for the plant’s new protoplasm in its cells, the production of chlorophyll, leaf growth, overall size, as well as vigor. In order to avoid unnecessarily leaching, farms must adhere to the directions for usage by the fertilizer company. For example, with Re-Nuble’s organic hydroponic nutrient, we have perfected its water solubility without requiring the 7-10 days typically to mineralize or break down the nutrients into a plant available form – and we’re so excited for farms to experience this breakthrough with us.
For part 3, we dive into organic nitrogen. Click here to read more.