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Posted on 11:30 AM by Wanto and filed under
By James Zacchaeus
The basic elements required for plant growth are usually regarded as potassium, phosphorus and nitrogen, and most proprietary brands of balanced fertiliser quote the percentage of these contained. Although these are of special importance all plants require, in addition, fairly considerable quantities of sulphur, calcium and magnesium, lesser, but still appreciable, amounts of iron, manganese, sodium, and minute quantities of other chemicals such as boron, zinc and so on, usually referred to as trace elements.
These elements are not present in the soil in pure form, being usually in compound form, that is a combination of one or more elements, mostly in insoluble form. Furthermore the plant is itself not capable of absorbing simple elements, but can only take up water soluble compounds.
Most of the required elements are present in varying degree in the soil, or are introduced or amplified by rain, or are supplied by the addition of composts and manures to the soil, but not always in sufficient quantities. Often, too, an excess of one mineral will, by prohibiting chemical reaction, lock up another element, so that, although present in the soil, the plant is not able to assimilate it.
This may appear to be a contradiction, but actually a plant can only absorb water soluble compounds and, as explained before, the majority of the required elements are present in an insoluble form.
Potassium is the plant tonic, promoting strong healthy growth and improving the quality of flower, as well as building up stocks of sugars and starches for use in storage elements. It helps also to build up the dahlias' resistance to adverse weather conditions. Potassium would appear to be in some measure complementary to nitrogen in that it helps to combat the effects of excessive nitrogen concentration, and also enables the plant to use the available nitrogen to the best advantage.
If the soil is deficient in potassium, the dahlias will tend to produce rather dwarfed and poor growth, whereas if potassium is contained in excess growth will tend to be extremely hard and the flowers will be produced late. Of the other elements there is sometimes a deficiency of iron, which will cause poor colour in the flowers and yellowing of the leaves, and, much more rarely, an excess which will have much the same effect as excess of potash although to lesser degree.
These elements are not present in the soil in pure form, being usually in compound form, that is a combination of one or more elements, mostly in insoluble form. Furthermore the plant is itself not capable of absorbing simple elements, but can only take up water soluble compounds.
Most of the required elements are present in varying degree in the soil, or are introduced or amplified by rain, or are supplied by the addition of composts and manures to the soil, but not always in sufficient quantities. Often, too, an excess of one mineral will, by prohibiting chemical reaction, lock up another element, so that, although present in the soil, the plant is not able to assimilate it.
This may appear to be a contradiction, but actually a plant can only absorb water soluble compounds and, as explained before, the majority of the required elements are present in an insoluble form.
Potassium is the plant tonic, promoting strong healthy growth and improving the quality of flower, as well as building up stocks of sugars and starches for use in storage elements. It helps also to build up the dahlias' resistance to adverse weather conditions. Potassium would appear to be in some measure complementary to nitrogen in that it helps to combat the effects of excessive nitrogen concentration, and also enables the plant to use the available nitrogen to the best advantage.
If the soil is deficient in potassium, the dahlias will tend to produce rather dwarfed and poor growth, whereas if potassium is contained in excess growth will tend to be extremely hard and the flowers will be produced late. Of the other elements there is sometimes a deficiency of iron, which will cause poor colour in the flowers and yellowing of the leaves, and, much more rarely, an excess which will have much the same effect as excess of potash although to lesser degree.
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