Abstract
Organic fertilizers and especially microbial biomass, also known as microbial fertilizer, can enable a paradigm shift to the conventional fertilizer-to-food chain, particularly when produced on secondary resources. Microbial fertilizers are already common practice (e.g. Bloom® and Synagro); yet microbial fertilizer blends to align the nutrient release profile to the plant’s needs are, thus far, unexplored. Moreover, most research only focuses on direct fertilization effects without considering added value properties, such as disease prevention. This study has explored three promising types of microbial fertilizers, namely dried biomass from a consortium of aerobic heterotrophic bacteria, a microalga (Arthrospira platensis) and a purple non-sulfur bacterium (Rhodobacter sphaeroides). Mineralization and nitrification experiments showed that the nitrogen mineralization profile can be tuned to the plant’s needs by blending microbial fertilizers, without having toxic ammonium peaks. In a pot trial with perennial ryegrass (Lolium perenne L.), the performance of microbial fertilizers was similar to the reference organic fertilizer, with cumulative dry matter yields of 5.6–6.7 g per pot. This was confirmed in a pot trial with tomato (Solanum lycopersicum L.), showing an average total plant length of 90–99 cm after a growing period of 62 days for the reference organic fertilizer and the microbial fertilizers. Moreover, tomato plants artificially infected with powdery mildew (Oidium neolycopersici), a devastating disease for the horticultural industry, showed reduced disease symptoms when A. platensis was present in the growing medium. These findings strengthen the application potential of this novel class of organic fertilizers in the bioeconomy, with a promising match between nutrient mineralization and plant requirements as well as added value in crop protection.
Highlights
Our industrialized global society is heavily dependent on synthetic inorganic fertilizers for primary crop production in both agriculture and horticulture
The goal of this study was to gain a broader understanding of the applicability across horticultural and agricultural for microbial fertilizers based on aerobic heterotrophic bacteria (AHB), MA and purple non-sulfur bacteria (PNSB), both individually as well as in blends
Aerobes and phototrophs as microbial organic fertilizers observed in the negative control, whereas divergent mineralization patterns were found for the different fertilizer treatments
Summary
Our industrialized global society is heavily dependent on synthetic inorganic fertilizers for primary crop production in both agriculture and horticulture. Serious environmental and economic repercussions [3]. When fertilizers are applied to the soil or in growing media (GM) for agricultural and horticultural applications, they are not completely consumed by plants, yet suffer from inefficiencies such as leaching, runoff and volatilization. For every 100 units of fertilizer applied to the land, only 4–14 units of nitrogen and 17 units of phosphorus are eventually consumed by humans [4,5,6]. A considerable portion of these fertilizers end up in the environment, resulting in detrimental effects on water quality (e.g. eutrophication), air quality (e.g. emissions of ammonia and nitrous oxide), the greenhouse gas balance (e.g. nitrous oxide), biodiversity and soil quality (e.g. acidification of soils) [7, 8]
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