Soil Fertility and Nutrient management (1+1)

A. Based on number of nutrients present

1. Straight fertilizers
Are those fertilizers containing or supplying only one plant nutrient element at a time. For e.g., Urea, Ammonium Sulphate (NH4SO4), Ammonium nitrate(NH4NO3), Single super phosphate (SSP), Muriate of potash(MOP- KCl).

2. Complex fertilizers
Fertilizers containing at least 2 or more of the primary essential nutrients (NPK). They are chemical mixtures, granular and free flowing and easy to apply. There are two types of complex fertilizers;
a. Complete or compound fertilizer: They are the chemical mixtures of three or more primary or major nutrient elements (NPK) in one compound or mixture. They are usually in granular form and easy to apply.
Ex: 10-26-26, 17:17:17, 19:19:19
b. Incomplete complex fertilizers: A fertilizer material lacking any one of three major nutrients or containing only two of the primary nutrients like N, P and K
Ex: N-P complex fertilizer : -Nitro-phosphate(Suphala:-15-15-0,20:20:0, -Diammonium phosphate: 18-46-0
Characteristics of complex fertilizers (CF)
1. They usually have a high content of plant nutrients. As such they are also called high analysis fertilizers.
2. They usually have a uniform grain size, granular form and good physical condition during storage.
Advantage of complex fertilizers
1. In one application we can supply more nutrients and need not apply separately.
2. Balanced nutrition can be achieved.
3. Less cost is involved in transportation and application.
4. They are available in different grades according to need of the soils and crops.
5. Being granular, it is easy to apply by broadcasting.
6. Some complex fertilizers also provides some micronutrients to soil.
7. Transport and distribution is easy
8. They are non-caking and non- hygroscopic, thus safer for storage

3. Mixed Fertilisers Or Fertiliser Mixtures
A mechanical/physical mixture of two or more straight fertilizer materials in suitable proportion is referred to as fertilizer mixture or mixed fertilizers. Sometimes, complex fertilizers containing two plant nutrients are also used in formulating fertilizer mixtures. Specific fertilizer grades are recommended for specific crops depending upon the soil and climatic conditions of the region.
The mixed fertilizers are usually in powder form or sometimes granular form. Fertilizer mixture (FM) are free flowing and easy to apply. The mixed fertilizers can be made according to the need of the crop and there is wide scope for adjusting the fertilizer ratio..
Guide for mixing fertilizers
Some fertilizers cannot be mixed with other fertilizers. Mixing of incompatible fertilizer leads to a loss of some of the nutrients in the form of gas, converting soluble nutrients into insoluble form or caking. Certain fundamental principles are to be followed in mixing fertilizers are.
1. Ammonium sulphate, ammonium chloride and other ammonical fertilizers and nitrogenous organic manures should not be mixed with lime
2. Urea should not be mixed with Super phosphate(SP)
3. Calcium cyanamide, basic slag, quick lime slaked lime should not be mixed with N in NH4-N form.
4. Super phosphate should not be mixed with lime or CaCO3 or wood ashes.
5. NaNO3 or KNO3 should not be mixed with Super phosphate.
6. Ammonium sulphate, nitrate should not be mixed with lime.
7. Nitrochalk should not be mixed with SP or lime.
The commonest fertilizer mixture can be made from SSP, Ammonium sulphate, SOP, Bonemeal, and MOP.
Advantages of fertilizer mixtures
1. Less labour is required to apply fertilizer mixture to soil. Individual crop wise fertilizer mixture can be made.
2. Balanced nutrition can be achieved.
3. The residual acidity of fertilizers can be effectively controlled by adding liming materials in the mixtures.
4. Micronutrients can be incorporated in fertilizer mixtures.
5. They have a better physical condition and more easily applied.
6. There is no need of purchasing straight fertilizers separately.
Disadvantages of fertilizer mixtures
1. Does not permit application of individual nutrients according to the needs of crops during specific times.
2. The unit cost of plant nutrients is higher than of straight fertilizer.
3. Lack of knowledge about proper mixing and their use.
4. Fertilizer mixture of particular grade suitable for particular crop cannot be applied for all crops.
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