Abstract
As soil and soilless culture systems are highly dynamic environments, the structure of rhizosphere microbial communities is consistently adapting. There is a knowledge gap between the microbial community structure of soil based and soilless culture systems and thus we aimed at surveying their impact on diversity and composition of bacterial communities across a 10-month period in a tomato cultivation system. We compared community metrics between an soil based culture system fertilized with malt sprouts and blood meal, known for its slow and high mineralization rate, respectively and a soilless culture system fertilized with fish effluent or supplemented with an liquid organic fertilizer. Bacterial and fungal community composition was followed over time using two complementary techniques, phospholipid fatty acid analysis and 16S rRNA amplicon sequencing. Nitrogen dynamics and plant performance were assessed to provide insight on how bacterial diversity of soil and soilless microbial communities ultimately impacts productivity. Similar plant performance was observed in soilless culture systems and soil based system and yield was the highest with the aquaponics-derived fertilizer. Soil and soilless cultivating systems supplemented with different nitrogen-rich fertilizers differed on its characteristics throughout the experimental period. Fast-paced fluctuations in pH(H2O) and nutrient cycling processes were observed in growing medium. Physicochemical characteristics changed over time and interacted with bacterial community metrics. Multivariate analysis showed that plant length, pH, Flavisolibacter, phosphorus, chloride, ammonium, potassium, calcium, magnesium, sodium, electrical conductivity, nitrate, sulfate, and the bacterial genera Desulfotomaculum, Solirubrobacter, Dehalococcoides, Bythopirellula, Steroidobacter, Litorilinea, Nonomuraea were the most significant factors discriminating between natural soils supplemented with animal and plant by-products. Long-term fertilizer regimes significantly changed the PLFA fingerprints in both the soilless culture and soil based culture system. The use of these by-products in the soil was positively associated with arbuscular mycorrhizal fungi (AMF), which may influence rhizosphere communities through root exudates and C translocation. Community structure was distinct and consistently different over time, despite the fertilizer supplementation. The fungal microbial community composition was less affected by pH, while the composition of the bacterial communities (Actinomycetes, Gram-negative bacteria, and Gram-positive bacteria) was closely defined by soil pH, demonstrating the significance of pH as driver of bacterial community composition. Fertilizer application may be responsible for variations over time in the ecosystem. Knowledge about the microbial interactions in tomato cultivating systems opens a window of opportunity for designing targeted fertilizers supporting sustainable crop production.
Highlights
Over the past century, incredible advancement has been achieved worldwide in increasing global agricultural production (Ramankutty et al, 2018) The production has more than tripled between 1960 and 2015, owing predominantly to the Green Revolution technologies and a significant enlargement in the use of land, water and other natural resources for agricultural purposes (FAO, 2016; Ramankutty et al, 2018)
The grow bag (GB) were filled with an organic growing medium made of 40% v/v sod peat, 40% v/v Irish peat and 20% v/v coconut fiber
For most of the European countries and for all member states of the European Union (EU), organic farming is strictly defined by the European Commission (EC) and these rules were followed for the soil based system
Summary
Incredible advancement has been achieved worldwide in increasing global agricultural production (Ramankutty et al, 2018) The production has more than tripled between 1960 and 2015, owing predominantly to the Green Revolution technologies and a significant enlargement in the use of land, water and other natural resources for agricultural purposes (FAO, 2016; Ramankutty et al, 2018). In order to meet the agricultural demand in 2050 we will need to produce 50% more food (Alexandratos, 2009; Foley, 2011; McKenzie and Williams, 2015). This expansive food production comes at a hefty cost to the natural environment (Notarnicola et al, 2017). The time has come for another look at using the tools of nature to enhance the intrinsically plant biological systems This doesn’t implicit an anti-chemical approach: rather, make agricultural practices both more productive and more sustainable by incorporating the generation of biologically sourced tools into existing practices
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