Organic Fertilization of Growing Media: Response of N Mineralization to Temperature and Moisture

Abstract

Managing plant fertilization is a major concern of greenhouse growers when it comes to sustainable production on growing media. Organic fertilization is popular, but more difficult to control since organic compounds first need to be mineralized by microbes. The objective of this study was to characterize the time course of N mineralization by different fertilizer–growing media pairs, in the absence of plants. Several incubations were carried out at four temperatures (4, 20, 28, and 40 °C) and three suction potentials (−3.2, −10, and −31.6 kPa) on four growing media under two organic fertilization conditions to study the dynamics of NH4+ and NO3−- production. The results showed that the release of mineral N was strongly dependent on growing media, temperature, humidity, and fertilizer nature, varying from 10.7% to 71.3% of the N fertilizer applied. A temperature action law was established for the four growing media. The Q10 value of the growing media was 1.13, lower than the average Q10 value of arable soils. On the other hand, the specific behavior of the growing media did not yield a single humidity action law. Nevertheless, the nitrification process, evaluated by analyzing the ratio of NO3− to total mineral N, showed a humidity-dependent relationship common to the four growing media and comparable to admitted observations on soils. Nitrification was optimal when growing media humidity was higher than 0.46 v/v.

Prediction of nitrogen mineralization in organically fertilized growing media for soil‐less production

“…N mineralization in different GM types is fully described in Cannavo et al (2022), where temperature and moisture effects are quantified, and the mechanisms of regulation of nitrogen mineralization are discussed. We showed that in 49 days, 25%-70% of the fertilizers were mineralized at the temperature of 20 or 28 • C, depending on the GMs and the fertilizers, and that the mineralization plateau could be reached from 28 days of incubation.…”

“…The fertilizer compositions are presented in Table 2, but their commercial names were kept confidential. The experimental design for collecting the dataset is fully described in Cannavo et al (2022).…”

“…The four GM were relatively similar in terms of physicochemical properties, even if they were made from different materials and intended for different cropping purposes, except GM3 (Cannavo et al, 2022). Consequently, the different mineralization rates (k) probably came from GM-specific microbial communities, depending on their origin and on the GM manufacturing process (Montagne et al, 2015(Montagne et al, , 2017 and activity (Cannavo et al, 2022;Paillat et al, 2020). Furthermore, fertilizer physical characteristics (material density and fiber hardness) and chemical protein depolymerization by microbes can impact k values (Paillat et al, 2020;Wang et al, 2016;Zhang et al, 2018).…”

“…Dion et al (2020) explained these differences by the fact that each organic fertilizer supported contrasting bacterial communities and had a distinct N mineralization rate mostly depending on their C:N ratio and biochemical composition in nutrients other than N. InCannavo et al (2022) only two organic fertilizers were used under modulated temperature and humidity conditions. Overall, this should be verified in a large study involving contrasting GM and organic fertilizers.…”

Optimising Soilless Culture Systems and Alternative Growing Media to Current Used Materials

“…The application of organic fertilisation is complex because organic compounds first need to be mineralised. Cannavo et al [10] reported that the release of mineral N is strongly dependent on the growing media, temperature, humidity, and fertiliser used. However, as the results described in this study were only derived from incubation trials, they should be additionally verified using plant experiments.…”