Growing media and organic fertilizers affect microbial activities and nutrient availability in soilless horticulture

L. Paillat, R. Guénon, L. Huché-Thélier, F. Barraud, P. Cannavo
Increasing concerns of environmental impact from plant production encourages the diversification of growing media (GM) and fertilizers to include sustainable organic materials. Organic fertilization and how microorganisms mediate its mineralization are not well understood. Hydric and biochemical properties of GM are suspected to drive microbial activity in response to organic fertilizer addition and its quality. We conducted a lab-experiment to investigate microbial activity and nutrient release in several GM and fertilizer combinations. We combined three GM (peat, coir and bark) and three organic fertilizers (horn meal and two plant-based fertilizers). Each GM-fertilizer combination was incubated at 25°C. After 7, 14, 28 and 56 days, we measured pH, electrical conductivity, nutrient contents (NH4+-N, NO3--N, PO43--P, SO42--S), and enzymes activities (β-1.4-glucosidase, acid phosphatase, arylsulfatase). There were significant differences between GM and fertilizer combinations in microbial function confirming that GM type affected microbial response to fertilizer. Nitrification was the fastest in bark and the slowest in peat, the latter resulting into high ammonium content for the plant-based fertilizers. Nitrification was delayed by 7 days in coir, but recovered after 56 days. Phosphate content was low in bark throughout the experiment as were phosphatase activities. Phosphate content increased with time in coir and peat with plant-based fertilizers whereas phosphatase activity only increased in coir. Whatever the GM, sulfate content was high from the beginning (day 7) especially with plant-based fertilizers, while arylsulfatase activity was only induced in coir. Overall, there is a future challenge in mixing these materials in order to combine their positive effects on nutrient availability regarding plant needs.
Paillat, L., Guénon, R., Huché-Thélier, L., Barraud, F. and Cannavo, P. (2020). Growing media and organic fertilizers affect microbial activities and nutrient availability in soilless horticulture. Acta Hortic. 1296, 791-798
DOI: 10.17660/ActaHortic.2020.1296.100
mineralization, enzyme activities, organic substrate, horn, nitrogen, phosphorus, sulfur

Acta Horticulturae