Nitrogen Availability in Organic Culture

Ensuring an adequate supply of nitrogen for organic growth isn’t always easy, explains Jean-Pierre Fortin (Ph.D.). You have to take different biological processes into account, including mineralization and nitrification, and you need to monitor constantly.

Organic culture, a market segment undergoing rapid growth, presents a real challenge to growers. The goal is to have the yields of conventional growing methods, without access to the same inputs. This problem is apparent with fertilizers, among other issues. A good assortment of natural fertilizers exists, but the availability of nitrogen in these products is not the same as with synthetic fertilizers.

Mineralization

The availability of nutrients varies with their solubility but also, in the case of organic products, according to the mineralization process. You need to consider that plants do not absorb nutrients in organic form; these elements need to be transformed into mineral form to become available to the roots. This transformation is assisted by microorganisms. These consume the carbon present in organic matter, which transforms complex molecules into simpler elements while liberating minerals. That’s the mineralization process. Mineral material is liberated in large part upon the death of the microorganism.

Mineralization is influenced by temperature. The growth of microorganisms, and therefore the mineralization of nutrients, proceeds much faster at elevated temperatures. The problem is the elements in natural fertilizers are not completely available when organic fertilizer is incorporated into the soil or applied during culture. Besides the soluble fraction that is immediately available, we need to allow for a delay between application and mineralization, which make the minerals available for growth.

Nitrification

Furthermore, it’s important to note that the soluble portion of nutrients does not always contain minerals in a form available to plants. The most striking example is nitrogen. In many organic fertilizers, the soluble portion is completely or almost completely dominated by Ammonium nitrogen (N-NH4) to the detriment of Nitrate nitrogen (N-NO3), which is the most desirable form. Here again, a transformation has to take place: this phenomenon is called nitrification.

Microorganisms transform ammonium into nitrite (NO2-), and then the nitrite into nitrate (NO3-). The graph below shows the concentration of N-Nitrate which was analyzed in soil undergoing organic culture. We can see that the availability of nitrogen is highly variable and at times almost zero.

Note that natural fertilizer was added at the end of March/beginning of April, which explains the first large fluctuation. The second, in July, is due to the warmth of summer, which accelerates biological processes making the Nitrate Nitrogen more available.

Thus, as pointed out by Régis Larouche, a consultant at Agrisys, the availability of nitrogen is a complex process in organic agriculture. Temperature, water management and the addition of natural fertilizers must be constantly recorded, revised and adjusted as a function of the daily needs of the crop. Here are a few measures you can take to ensure sufficient nitrogen for your organic growing needs:

Increase the growing temperature;
When it’s cold out, increase the nutrient supply to meet the plant’s needs;
Store soil mix and fertilizer in a temperate or heated space;
Vary the nutrient supply as a function of the time of year.

Using controlled-release fertilizer for a value-added product

Do you know that plants are often not fertilized after the sale, in the retail market? Take advantage of this opportunity by offering a value-added product to your customers: offer plants with controlled-release fertilizer.

A University of Florida’s research shows that, compared to the simple use of water-soluble fertilizers, the use of controlled-release fertilizers increases the value and quality of your plants products (Improve Post-Production performance for your Customer with Residual Controlled-Release Fertilizer by Sueyde Oliveira and Dr. Paul Fisher).

This technique can also increase your profitability. Your plants will stand out from the competition by being more supplied and abundant when buying by the consumer and will have a better long-term growth.

Producers, Retailers and Consumers; everyone is winning!

Tips

To make your life even easier, we offer you the option of adding controlled-release fertilizer directly to your Fafard soil mix, at the quantity you want. Contact your representative for more details!

A Technical Team for Service All of Your Needs

Our scientific staff can service all of your needs for physical or chemical analysis; whether for water quality, nutrient solutions or the substrate itself. Our experts are available to visit you on site to understand your needs and requirements. They may also provide you wise advice to optimize products performance, fertilization processes or your watering system.