The question of the choice of fertilizers does not lose relevance for gardeners. But it is not easy to buy the right product - there are many of them on the market, and not everyone can figure it out.
The main requirements remain unchanged: top dressing should stimulate yield and not overdry the soil.
We learn more about one of these compositions, considering what constitutes “Double Super Phosphate” and what useful properties its formula hides.
Description and composition
This fertilizer is obtained by the action of sulfuric acid on natural raw materials (actually phosphates). In general, the production looks like this: raw materials are decomposed at temperatures above +140 ° C, after which granulation is carried out, followed by drying in a special drum.
In order to "squeeze" the maximum of useful properties and increase the shelf life, the resulting mass is treated with ammonia or chalk.
The result is a composition, the main active element of which is monohydrate calcium dihydroorthophosphate. Chemists designate it as Ca H2O4 with the indispensable addition of H2O. 
Important! On sale there are packagings on which the different quantity of phosphorus contained in granules is indicated. This is not a fake - manufacturers produce fertilizer brands A and B, which use different proportions of the main elements.
Already in this formula, you can see the difference from the standard superphosphate - "double" does not contain calcium sulphate admixture (and it acts as a ballast, increasing the weight).
In these grays of gray color contains:
- phosphorus (43-55%);
- nitrogen (up to 18%);
- calcium (14%);
- sulfur (5-6%).
- microcomponents in the form of manganese (2%), boron (0.4%), molybdenum (0.2%) and zinc with iron (0.1% each). The share of other elements is an order of magnitude less.
It dissolves well in water (due to the absence of gypsum), although not always willingly. On the other hand, this inconvenience is offset by a number of useful qualities. 
Advantages over others
This fertilizer is attractive because:
- does not contain "binding" ballast;
- better stimulates growth;
- thanks to nitrogen, the number of ovaries on plants increases, and this is already the prospect of a greater yield;
- sulfur "tones up" seedlings, increasing their vitality. When used for grain crops, cereals more actively accumulate protein (and in oily species, seeds become fatter);
Did you know? The pioneer of phosphorus is considered Gennig Brand. Like all alchemists, the German conducted a lot of experiments in the hope of finding the elixir of life or something like that, but in 1669 received an unknown until then luminous substance.
- not highly toxic;
- the granules do not clot, which is convenient for long-term storage.
The list is impressive, and the arguments are quite weighty. But any fertilizer, including double superphosphate, will be useful only if you comply with all requirements, which are reminiscent of instructions for use.
Where applicable
The fertilizer has no dangerous contraindications and is allowed for use both in small kitchen gardens and in fields where grain is grown industrially.
A separate topic - compatibility with different types of soils. For chernozem, a moderate dosage is recommended for infrequent treatments. Weaker alkaline soils will more readily accept an extra dose of such a “drug”.
But in the case of acidic soil will have to take less, because phosphorus in combination with calcium strongly oxidizes the fertile layer. 
The “double” is not used on too saline areas - phosphate can simply not dissolve. Concentrate can be used several times per season.
Important! Medium acid soils can be healed. To this end, lime (500 g) or wood ash (200 g) is added to 1 square meter. True, phosphate compounds on such a soil can be used no earlier than one month after preparation.
The main application is in April or September. In this case, the tool is placed shallowly, at the level of the seeds. In case of surface application, digging is required (otherwise, phosphorus is absorbed unevenly on the area).
In May, when sowing and planting, basic feeding is done - the granules are put in the right quantity in the hole, at the same depth as the seedlings.
As required, the current treatment is carried out, if the ovary is weakened or the leaves have become unhealthy purple hue. This is where nitrogen comes in, which has a beneficial effect on the vegetative system. 
For what crops is suitable
The list of "customers" of this tool is very wide, it includes almost all cultivated varieties of vegetable, fruit and grain plants.
On top dressing excellent response:
- cucumbers;
- tomatoes;
- cabbage;
- carrot;
- pumpkin;
- beans;
- raspberries and strawberries;
- Apple tree;
- cherry;
- pear;
- grapes
Rarely, but still require phosphorus additives onion, pepper and eggplant. They can also add currants and gooseberries. More hardy beets, radishes and radishes lack of phosphorus is not so terrible. 
Did you know? In the old days, some churchmen used phosphorus to "update" icons painted in white. Over time, they darkened, but after wiping with a cloth moistened in hydrogen peroxide, they acquired a lighter shade — black sulphide (white base) reacted, turning into lead sulphate. The population did not delve into these subtleties, and the whole district went to look at the transformed face.
There are some nuances. If double superphosphate is taken as the main fertilizer for tomatoes or other garden plants, the application scheme is described in detail on the package. With "farming" the cultures are a bit more complicated.
For two of them (corn and sunflower) direct contact of the pellets with the seed is undesirable. They are given smaller doses (as an option - they drop the fertilizer a little deeper). With other grain such problems do not arise.
Application rates
When planning such a treatment, many "mix" phosphates with other compounds. Such mixtures give a more tangible effect (of course, if you correctly calculate the proportions). 
"Double" can be combined with potash fertilizers (for spring application) or with nitrogen and potash agents (for autumn procedures). It is strictly forbidden to interfere with it. with urea, lime or chalk - with them, superphosphate reacts immediately, becoming at the same time a "dummy".
You can often hear the question of how to dissolve the purchased double superphosphate in ordinary water. The easiest way to add 450-500 g of the substrate in 5 liters of warm water, thoroughly mixed. Look at the liquid: if there is no sediment, it can already be used (while its presence indicates a poor-quality product).
Important! Dolomite and saltpeter (especially sodium) are not suitable for the preparation of mixtures with saturated phosphates.More familiar mixtures with "natural products" remain more popular and economical:
- 120-150 g of pellets are poured into a moistened bucket of raw manure;
- mix thoroughly;
- insist 2 weeks (this is mandatory).
The method is not the fastest, but still effective: phosphorus retains the nitrogen compounds contained in the manure. 
We turn to the norms of consumption. They depend on the time and method of making the prepared mixture, as well as a specific culture. Here everything is extremely simple:
- on the "vegetable" site or under the greens make 35-40 g / sq. m (for poor soil on the same area you can add no more than 10-12 g);
- corn requires at least 120 kg with a maximum of 170 kg (here the bill is already on hectares);
- 125-130 kg / ha will be sufficient for spring varieties;
- on the eve of autumn or spring digging, you can evenly scatter the granules on the site at the rate of 2-3 kg per "weave";
- in the autumn rims of adult fruit trees in the autumn evenly sprinkle about 0.5 kg of fertilizer with further digging;
- when planting seedlings in the wells (flush with the root) make about 3 g of this tool. Double superphosphate fertilizer is also useful for potatoes, its use is reduced to the same quantities and terms.
Did you know? At the beginning of the twentieth century, the means of protection did not differ in reliability, so many chemists working with phosphorus literally glowed in the dark (gases were absorbed into their clothes). City rumors immediately filled with rumors about "ghosts" and "luminous monks", although mysticism has nothing to do with it.
As you can see, the processing scheme is simple, and the results are decent. We hope this information will help you collect a record harvest. And let the visits to the cottage bring only positive!
