Confused about all the different bottles of "plant food" - some claiming to be "organic" and some not? Here we explain what the essential difference is.
Hydroponic nutrients contain a precise balance of elements needed by your plants to grow and bloom. Liquid hydroponic nutrients are derived from mineral salts that have been mined from the earth and then chemically synthesized using fossil fuels to create inorganic fertilizers. These fertilizers are in an ionic form that plant roots can access and assimilate immediately.
Hydroponics is a preferred method of cultivation, especially commercially, because the grower can control exactly what nutrition is available to the plant. When factors such as nutrient pH, strength and temperature are well managed the results can be astonishing-huge production is possible from the smallest of spaces.
Crucially hydroponic growers do not need soil to grow their plants in. Some pure hydroponicists grow their plants with roots submerged in an aerated nutrient solution (deep water culture) or a shallow, perpetually flowing stream of nutrients (Nutrient Film Technique) whereas others use an inert material such as rockwool, perlite, vermiculite, coco coir or expanded clay pebbles to act as a rooting medium. Hydroponic growers can use inert (nutrient-free) materials because all of the nutrients their plants need are supplied by the nutrient solution.
Organic nutrients should really be called organic inputs, rather than nutrients. These inputs are not directly usable by plants. They first need to be assimilated by bacteria and microbes present in the soil. These bacteria and microbes can also be brewed at home in a compost tea.
Organic inputs include sugar beet extracts, worm castings, guano, animal manures, compost, blood meal, bone meal, fish products (meal/emulsion/hydrolysate), alfalfa meal, feather meal, seaweed, unrefined naturally occurring minerals (glacial rock dust, soft rock phosphate, Epsom salts) and many, many more. Manufacturing liquid organic nutrients is a complex process that involves the selection of key ingredients that will remain stable and soluble.
Mineral Based Fertilizers and Soil
Another method, sort of half covered by each of the sections above, is to use mineral-based fertilizers with soil. This is a great way of delivering nutrients fast to plants growing in soil. Some organic growers claim that such practices can cause irrevocable damage to soils-particularly to the microbial population. It's true that chemical inputs such as anhydrous ammonia will locally reduce microbial numbers but the microbe population quickly bounces back.
Some growers try and best of both worlds approach, using a mixture of mineral inputs (to drive the nitrogen-hungry vegetative stage) and organic inputs to drive the flowering and fruiting stage.
What is microbial mineralization?
Planet Earth as one giant compost heap! The job of soil microbiology is to cycle organic matter back into a form that plants can use. It's the reason why our rainforests thrive year in, year out without any additional fertilizer!
Organic growers often argue that their chosen method is more sustainable as it does not rely on large quantities of fossil fuel energy required to purify this finite mineral resource. But when it comes to resources, there's none so precious to us than fresh water. Hydroponic growers using re-circulating growing systems use up to 90% less fresh water than organic growers.
Organic growers focus on 'feeding the soil.' The soil, or rather, the microbiology within it, does the 'work' of getting water and nutrients to the roots. Hydroponic growers deliver what their plants need directly in the form of a nutrient solution-no microbiology required.
Final Thought: Bioponics - The Best of Hydroponics and Organics?
William Texier from General Hydroponics Europe has developed a concept he calls 'Bioponics' - a soluble, organic nutrient that remains stable in a reservoir. Some ions are immediately available to the plant (but are still from organic origin) whereas some organic molecules are larger and require decomposition over a few days. This fast decomposition process is activated and sustained by the introduction of beneficial microorganisms contained within a 'biofilter', in which bacteria and fungi (particularly Trichoderma harzianum) feed on the carbon part of organic molecules and release the ions attached to them, which is exactly what plants are looking for.