Growing Medium Type Affects Organic Fertilizer Mineralization and CNPS Microbial Enzyme Activities

Abstract

Managing plant fertilization is a major concern of greenhouse growers to achieve sustainable production with growing media (GM). Organic fertilization is popular but is more difficult to control, since organic compounds need first to be mineralized by microbes. After 7, 14, 28, and 56 days of incubation, we investigated the response of microbial activities and nutrient releases from three frequently used organic fertilizers (horn and two plant-based fertilizers) in three frequently employed GM types (peat, coir, and bark). We measured pH, electrical conductivity, nutrient contents (NH4+-N, NO3−-N, PO43−-P, SO42−-S), and enzyme activities (β-1.4-glucosidase, urease, acid phosphatase, arylsulfatase). After fertilization, microbes in coir expressed all the C, N, P, and S functions studied, making related nutrients available. In peat and bark, some C, N, P, and S-related pathways were locked. Peat presented high NH4+-N and PO43−-P releases linked to high acid phosphatase and β-glucosidase activities, while bark showed high nitrification rates but weak enzyme activities. Fertilizer types modulated these responses with lower activities and nutrient releases with horn. Our results contributed to better understanding mineralization processes in GM, showing different microbial responses to fertilization. This study pointed out the necessity to look deeper into microbial functions in GM optimizing biological and physicochemical properties.

The Evolution of Soilless Systems towards Ecological Sustainability in the Perspective of a Circular Economy. Is It Really the Opposite of Organic Agriculture?

“…In contrast, organic constituents (such as coconut fiber or green waste compost) or their mixture contained bacterial ammonia oxidizers and nitrifiers [29]. In any case, among organic growing media, each substrate drove nitrogen mineralization and nitrification after organic fertilization according to its own chemical and biological features: peat was distinguished for a weak nitrification due to its low pH, while bark showed low microbial enzyme activities independently on the added organic fertilizer [30]. In most cases, organic fertilizer types modulated microbial activity of growing media, finding, for example, lower activities and nutrient release with horn meal than with plant-based fertilizers [30].…”

“…In any case, among organic growing media, each substrate drove nitrogen mineralization and nitrification after organic fertilization according to its own chemical and biological features: peat was distinguished for a weak nitrification due to its low pH, while bark showed low microbial enzyme activities independently on the added organic fertilizer [30]. In most cases, organic fertilizer types modulated microbial activity of growing media, finding, for example, lower activities and nutrient release with horn meal than with plant-based fertilizers [30]. It is generally concluded that it is relevant to define an adequate fertilization strategy, made by selected media components and organic fertilizer type, to obtain a known nitrifying community that allows one to predict and control the microbial nitrogen conversion and delivery to plants [29,30].…”

“…In most cases, organic fertilizer types modulated microbial activity of growing media, finding, for example, lower activities and nutrient release with horn meal than with plant-based fertilizers [30]. It is generally concluded that it is relevant to define an adequate fertilization strategy, made by selected media components and organic fertilizer type, to obtain a known nitrifying community that allows one to predict and control the microbial nitrogen conversion and delivery to plants [29,30]. When compared to an organic soil growing system, soilless cultivation of tomato on prevalent peat-based substrate organically fertilized (with fish effluent or liquid organic fertilizer) showed that a bacterial and fungal community promptly occupied the growing medium and the whole rhizosphere.…”

Meat Processing Waste as a Source of Nutrients and Its Effect on the Physicochemical Properties of Soil

“…Similar to other organic fertilizers, MBM is a slow-release fertilizer containing N and P that are unavailable for uptake by plants [36]. In soil, they are converted to plant-available mineral forms via biophysicochemical processes [33,37]. The rate of mineralization of organic compounds in soil depends on its temperature, physical properties (moisture content, structure, and granulometric composition), chemical properties (composition of the introduced organic matter), the C/N ratio, and the activity of soil-dwelling microorganisms [38].…”

Liquid Organic Fertilizer Effects on Growth and Biomass of Lettuce Grown in a Soilless Production System

“…However, microflora are absent in soilless systems. Therefore, mineralization of OF sources in soilless systems are affected, and thus the bioavailability of nutrients to the plant is also reduced Paillat et al, 2020). For this reason, use of OFs that do not require further mineralization is important for optimizing organic vegetable production under soilless greenhouse conditions (Bi et al, 2010).…”