Plant couldn't have source it's nutrients from other medium but soil and all the physical and chemical processes requires of plant to complete their life cycle are carried out on and within the soil.
Plant requires combination of synthesize food I.e produce food through photosynthesis and absorb nutrients element from the soil to complete their life cycle. However there is a need to trace record on soil formation and historical perspective of how plant feed so as to have better understanding of plant nutrition.
Soil formation......
Soil forms from parents materials, have some mineral element inherent in them I. E from their sources. These are made available to plant for uptake after undergoing different chemical processes and reactions.
Note:.....
The process of having soil from parent materials is called pedogenesis. ( The smallest unit of soil is pedon, the aggregate of soil is PED, soil as in the solid form, liquid and gaseous. Humus is the organic layer of the top soil.
Historical perspective of how plant feed.......
Studies on how plant feed could be trace back to 350BC during the days of Aristotle when humus theory was proposed to explain plant nutrition. However, application of chemistry to agriculture terms, agricultural chemistry gives a scientific understanding of plant nutrition which are itemized as follow.......
That mineral substances are not found by chance in the plant, they are essential component of plant.
That plant requires the sixteen mineral element refer to as essential elements.
Plant needs different quality of the mineral elements.
Many soil exhibit lack of nutrients element which can be restored through application of fertilizer
Humus is not required by plant as nutrient element, however it is required as source of nutrients element.
Thanks
Elizabeth