A chemical fertiliser is defined as a compound fertiliser, which contains two or more components of the main nutrients, such as N, P, K, and so forth. A binary composite fertiliser contains two major nutrients, a ternary composite fertiliser contains three major nutrients, and a multi-compound fertiliser contains more than three nutrients.
The classification of compound fertilisers according to their manufacturing process comprises three categories: chemical compound fertilisers, compound fertilisers and mixed compound fertilisers. A chemical compound fertiliser is created through a chemical process, as exemplified by potassium phosphate. A compound fertiliser is a product manufactured by a fertiliser manufacturer that contains two or more kinds of monomaterial fertiliser. It is produced through a specific processing technology that involves re-granulating the fertiliser to create a product containing a variety of elements. This process often involves a partial chemical reaction, and the resulting product is typically referred to as a compound fertiliser. A mixed compound fertiliser is a product resulting from the mechanical mixing of several kinds of fertilisers. The process of production does not entail any chemical reaction; it is merely a mechanical mixing of the components. An example of a mixed compound fertiliser is ammonium chlorophosphate, which is produced by mixing ammonium chloride and ammonium phosphate.
The advantages of compound fertilisers include the presence of high active ingredients and a greater concentration of nutrients, a reduced number of side components, a lower risk of adverse effects on the soil, a lower production cost, and favourable physical properties.
The disadvantages of composite fertilisers include a fixed nutrient ratio, which makes it difficult to adapt to the varying needs of different soils and crops. Additionally, the need for single fertilisers to supplement the adjustment is often a drawback. It is challenging to align the requirements of fertilisation technology with the movement of various nutrients in the soil. The mobility of nitrogen fertiliser and that of P and K fertiliser are both limited, yet the subsequent effects of phosphorus and potash are considerable. In practice, nitrogen fertiliser is typically used as a fertiliser, phosphorus and potash fertiliser are usually used as a base fertiliser and seed fertiliser, and composite fertiliser is a variety of nutrients applied in the same position and at the same time. This makes it challenging to meet the crop’s nutrient requirements over a specific period. It is therefore essential to ascertain the soil conditions and the growth characteristics of the various crops, as well as the laws governing fertilisers and the application of suitable composite fertilisers.
Main types of compound fertilisers and their use
(1) Ammonium phosphate
Ammonium phosphate, called ammonium phosphate, is made from ammonia and phosphoric acid, and can be produced separately as monoammonium phosphate, diammonium phosphate and triammonium phosphate due to different degrees of ammonia and neutralisation. Today’s domestic ammonium phosphate is actually a mixture of monoammonium phosphate and diammonium phosphate. With an N content of 14%-18% and a P2O546%-50%, pure ammonium phosphate is grey-white, while with impurities it is dark grey. Ammonium phosphate is readily soluble in water, with a certain degree of hygroscopicity, and is usually added to the moisture-proofing agent in granular form to facilitate storage, transport and application.
Ammonium phosphate is suitable for a wide range of crops and soils, particularly for crops with high phosphorus requirements and phosphorus-deficient soils. The application of ammonium phosphate should first consider the amount of phosphorus, the lack of nitrogen can be used to supplement the single nitrogen fertiliser, ammonium phosphate can be used as a base fertiliser, fertiliser and seed dressing. As a base fertiliser and fertiliser, generally 10-15kg per 667m2 is appropriate, can be ditch or hole, as seed fertiliser per 667m2 to 2-3kg is appropriate, but should not be in direct contact with the seed to prevent the impact of germination and caused by seedling burning. Fruit tree base fertiliser up to 2.5kg per plant is appropriate, fertiliser can be used in the form of extra root fertiliser, spraying concentration 0.5%-1%. Ammonium phosphate can not be mixed with grass ash, lime and other alkaline substances, applied or stored, acid soils on the application of lime must be 4-5 days before the application of ammonium phosphate, so as not to cause the loss of nitrogen volatilisation and reduce the effectiveness of phosphorus.
(2) Ammoniated calcium superphosphate
In order to remove the adverse effects of free acid in calcium superphosphate, usually in the calcium superphosphate into a certain amount of ammonia made of ammoniated calcium superphosphate, its main components are NH4H2PO4, CaHPO4 and (NH4)2SO4, containing N2%-3%, P2O513%-15%. Ammoniated calcium superphosphate is dry, loose, soluble in water (phosphorus is weakly acid soluble), does not contain free acid, not corrosive, hygroscopicity and agglomeration are weak, physical properties are good, the nature of the more stable.
Ammoniated calcium superphosphate is slightly better than calcium superphosphate, suitable for all kinds of crops, the best effect in the application of acidic soil, pay attention to the alkaline substances must not be mixed to prevent the volatilisation of ammonia and phosphorus degradation. Due to its low nitrogen content, it should be used with other nitrogen fertilisers and its application method is the same as for calcium superphosphate.
(3) Potassium Dihydrogen Phosphate
Potassium dihydrogen phosphate is a kind of high concentration of phosphorus and potassium binary compound fertiliser, the pure product is white or grey-white crystals, nutrient 0-52-34, hygroscopicity is small, physical properties are good, easily soluble in water, aqueous solution pH3-4, expensive.
Potassium dihydrogen phosphate is suitable for seed dipping, seed mixing and extra root fertiliser. Seed dipping concentration is 0.2%, time is 12 hours, per 100kg solution dipping 30kg soybean, 50kg wheat, seed mixing is usually sprayed at 1% concentration, the same day mixing the seed into the soil. Spray concentration of 0.2%-0.5%, per 667m2 dosage of 50kg-75kg liquid, choose in the afternoon on a sunny day, to the extent that the foliar spray does not drip on the ground. Wheat in emergence, cotton before and after flowering, spraying three times in succession. Fruit trees in fruit expansion to colouring period, spraying with 0.5% potassium dihydrogen phosphate solution to improve product quality has given good results.
(4) Potassium nitrate
Potassium nitrate, commonly known as fire nitrate, is produced by dissolving sodium nitrate and potassium chloride together and then recrystallising or extracting from nitrate soil, with the molecular formula KNO3, containing 13% N and 46% K2O. Pure potassium nitrate is white crystalline, crude products are slightly yellow, hygroscopic, soluble in water, chemically neutral, physiologically neutral fertiliser. It can easily explode at high temperatures and belongs to the group of flammable and explosive substances, therefore safety precautions should be taken when storing, transporting and using it.
Potassium nitrate is suitable for dryland fertilisation, the dosage is generally 5-10kg/667m2, it has a good fertilising effect on potatoes, tobacco, sugar beet, grapes, sweet potatoes and other potassium-loving and chlorine-avoiding crops, the response is also better on leguminous crops, when used on other crops it should be used with mono-nitrogen fertiliser to improve the fertilising effect. Potassium nitrate can also be used as an extra-radical fertiliser at a suitable concentration of 0.6-1%. In dry areas it can also be mixed with organic fertilisers as a basic fertiliser at a rate of about 10kg/667m2.
As the N:K2O ratio of potassium nitrate is 1:3.5, the potassium content is high, so the fertiliser calculation should be based on the potassium content, and the nitrogen deficiency can be supplemented with straight nitrogen fertiliser.
(5) Urea ammonium phosphate
Urea ammonium phosphate consists of CO(NH2)2-(NH4)2HPO4, which is urea plus ammonium phosphate. Its nutrient content can be 37-17-0, 29-29-0, 25-25-0, etc. It is a kind of highly concentrated nitrogen and phosphorus compound fertiliser, in which the N and P nutrients are water-soluble, and the N:P2O5 is 1:1 or 2:1, which is easily absorbed and utilised by plants.
Ammonium urea phosphate is suitable for all types of soils and all types of crops, and its fertilising effect is better than that of mono-fertilisers with equal amounts of nitrogen and phosphorus, and its application method is the same as that of ammonium phosphate.
(6) Ammonium-phosphorus-potassium compound fertilisers
Ammonium-phosphorus-potassium fertilisers are ternary compound fertilisers consisting of ammonium sulphate, potassium sulphate and phosphate mixed in different proportions or consisting of ammonium phosphate plus potassium salt. Due to the different mixing ratios, the nutrient ratios are 12-24 -12, 10-20-15, 10-30-10. The phosphorus content of ammonium-phosphorus-potassium fertilisers is relatively high and can be combined with the use of simple nitrogen and potassium fertilisers to adjust the ratio and improve the fertilising effect. Ammonium-phosphorus-potassium fertiliser is a highly concentrated compound fertiliser which, together with potassium nitrate, is often used as a special fertiliser in tobacco areas.
In addition to the above, there are many types of compound (blended) fertiliser, some of which have been widely used in production with good results. Each region should choose the appropriate blended fertiliser according to different soil, climate, crop and production conditions.
