Fertilisers are plant nutrients .
Nutrients existing naturally in the soil, atmosphere, and in animal manure. However, naturally occurring nutrients are not always available in the forms that plants can use, or in the quantities needed. So we add to them by applying fertiliser, to make plants grow to their maximum potential.
Fertilisers can be classified into two categories: organic or inorganic.
Organic fertilisers are derived from living or once-living material, including animal wastes, crop residues, compost and numerous other by-products of living organisms.
Inorganic fertilisers are derived from non-living sources and include most of our man-made, commercial fertilisers. Man-made and natural fertilisers contain the same elements, but man-made fertilisers act more quickly .
Often, the soil doesn't hold enough of these nutrients in the quantities needed for desirable growth and production.
An element is considered essential if in its absence plant growth and reproduction is significantly hindered.
The nutrients, that are in the soil, are often used up and need to be replaced. Therefore, we need to add extra plant nutrients to obtain maximum plant performance.
We often see quotes by various agricultural sources in NZ, the amount of the likes of phosphorus, sulphur and calcium that are removed from the soil in meat, milk, bone and wool.
This, illustrates the importance of replacing these elements as they go out the farm gate, with the likes of superphosphate, which supplies phosphorus and sulphur.
Tissue studies of plants have found more than 60 different mineral elements, although it has generally been accepted that 16 -17 elements are essential for plant growth.
Many farmers in NZ are well aware of the consequences of low levels of copper or cobalt in pasture, and in some areas selenium, as well as magnesium (grass staggers), even iodine and zinc and in many cases calcium (as in milk fever).
There are many cases where several of the nutrients are missing or are at such low levels that supplementation of the animal is necessary, otherwise the animal would die or be severely undernourished.
Subclinical trace mineral deficiencies occur more frequently than recognized by many livestock producers and can be a bigger problem than acute mineral deficiencies, because the specific symptoms that are characteristic of a trace mineral deficiency are not seen.
Instead, the animal grows or reproduces at a reduced rate, uses feed less efficiently and operates with a depressed immune system. The end result is inefficient production and lower profitability.
When micro-nutrients become a limiting factor, water, fertiliser and other high-energy production inputs are wasted.
In most cases the elements needed by the plant are also needed by the animal which feeds on the plant.
Some elements needed by the animal are not required by the plant, but plants takes them up and makes them available to the animal, and therefore plays a significant role in animal health. Selenium, iodine and cobalt are examples.
Seven trace minerals, have been shown to be needed in supplementing animal diets. They are iron, copper, zinc, manganese, cobalt, iodine and selenium.
Soils are derived from weathered parent material.
If the original material was low in a particular element or non existant, so too is the resulting soil.
Soils can become depleted of minerals and trace elements which too are absorbed into the likes of meat, milk, bone, wool, vegetables and fruits, as well as the major elements, and many soils are naturally deficient in one or more of these elements.
Within a space of just a kilometre or two, soils can be radically different, with.localised deficiencies of trace elements like copper, cobalt or selenium.
Because our supply of minerals comes through the food chain, from the plants and animals we eat, and because these same minerals are essential ingredients of these same plants and animals, any that are missing can have serious implications for plant, animal and ultimately our own health.
One has to conclude then, that this is where fertilization should start.
Even though the major element solid type NPK fertiliser is required in the largest amounts, if used exclusively, sooner or later a deficiency of a minor element can occur in soils low in that particular element, and it too should be replaced.
Foliar nutrients can quickly correct a nutrient imbalance, and are by far the most effective way to apply micro nutrients or trace elements and supplement the major elements , because foliar nutrients are readily available and more easily utilized by the plant than soil nutrients.