Soil nutrients for food

For their growth crops feed on nutrients. Roots take up soil nutrients which, incorporated in the crop, make up part of our food. Soil nutrients are derived from various sources. Natural fertility, originating from slow release of nutrients by eroding bedrock or mineralizing organic matter, is associated with relatively low yields. This situation is worsened when this mineral stock can not keep pace with nutrient depletion resulting from frequent harvesting on the same piece of land. Resorting to other land (i.e. shifting cultivation) claims more soil area.

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Higher yields correspond with high nutrient uptake, implying application from supplementary nutrients from manure or artificial fertilizers. Additionally, soils may be repeatedly cultivated, as long as  harvested nutrients are sufficiently replenishing.

However, not all nutrients applied to the soil are readily available to crops. This is amongst others determined by soil type. Clay particles in particular may fix minerals while they prevent losses by leaching below the rooting zone.

Soil water availability is a prerequisite for crops taking up nutrients: as they become dissolved, nutrients absorbed by the roots are subsequently transported to other plant parts. This implies that bóth water and nutrients should be provided simultaneously by the soil to increase crop productivity.

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Biomass contains nutrients, of which nitrogen (N), phosporous (P) and potassium (K) are most notably, thus referred to as macro-nutrients. Other minerals such as iron (Fe), copper (Cu), manganese (Mn), and zinc (Zn) are present in substantially smaller quantities, and accordingly known as micro-nutrients.

The range in nutrient content (i.e. kg (nutrient) kg-1 (dry matter)) varies with plant species, plant part (e.g. leaves, storage organs) and the development stage of that particular plant part.

Nutrients, as intrinsic part of the harvested and subsequently consumed plant matter, play a vital role in human health. This is reflected by the nutritional properties of food in addition to its caloric value.

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