Fertilizer Mixtures (FM)
When two or more fertilizers are mixed together to supply two or three major elements i.e. N, P2O5 and K2O is known as fertilizer mixture or Mixed fertilizer. Or
A mixture of two more straight fertilizer materials is referred to as fertilizer mixture. Sometimes, complex utilizes containing two plant nutrients are also used in formulating fertilizer mixtures. Complete fertilizer refers to the fertilizers containing 3 major plant nutrients, N, P2O5 and K2O.
Types of fertilizers: There are two types of fertilizer mixtures:
a. Open formula fertilizer mixtures: The formulae of such fertilizers in terms of kinds and quantity of the ingredients mixed are disclosed by the manufacturers.
b. Closed formula fertilizer mixtures: The ingredients of straight fertilizers used in such mixtures are not disclosed by the manufacturers.
Materials used in fertilizer mixtures: Different materials go in to production of mixed fertilizers. In accordance with their principle function in the mixture, the materials can be grouped into:
1. Suppliers of plant materials: These are the straight fertilizers added to supply the plant nutrients mentioned in the grade, thus, are the primary materials most essential for preparing mixed fertilizers.
2. Conditioners: These are the organic substances which prepare the fertilizer mixture in good drilling condition and reduce caking. E.g.: Tobacco stems, Peat, Groundnut hulls and paddy hulls (Husks), bone meal, oilcakes.
3. Neutralizers of residual acidity: The substances used to neutralize the residual effects are known as neutralizers. For example, if the ‘N’-ous fertilizers used are acididic in nature like Amm. Sulphate, Urea, a basic material like lime stone is added to counteract the acidity.
4. Filler: Filler is the make – weight material added to a fertilizer mixture. It is added to make up the differences between the weight of the added fertilizers required to supply the plant nutrients and the desired quantity of fertilizer mixture, such as sand, soil, ground coal ashes, sawdust and other waste products.
5. Secondary and micro – nutrients: Some times, secondary and micro – nutrient carrying fertilizers are added to correct its deficiency.
An expression indicating the % of plant nutrient in a fertilizer mixture is termed as fertilizer grade and the relative proportion of major plant nutrients in the mixed fertilizer taking ‘N’ as one, called as fertilizer ratio. For example, in a fertilizer mixture of 6:12:6 grades, the fertilizer ratio is 1:2:1.
The low analysis fertilizers contain less than 25% of primary nutrients and the high analysis fertilizers contain more than 25% of primary nutrients. On the other hand, the low analysis mixed fertilizers contain less than 14% sum of the primary nutrients and high analysis mixed fertilizers contain more than 14% sum of the primary nutrients.
Advantages:
1. The balanced fertilizer mixture suited to crop and soil can be supplied,
2. All the required nutrients can be supplied at one time by the application of fertilizers mixture and thus, time and labourers are saved.
3. Storage and handling costs are reduced.
4. Micro nutrients can be incorporated.
5. Mixtures have better physical condition and are easier for application.
6. Residual acidity can be neutralized by using neutralizers in mixture.
Disadvantages:
1. The cost of plant nutrients is higher than straight fertilizers.
2. All only one nutrient is required by the crop, the fertilizer mixtures are not useful and sometimes farmers may add nutrients in excess or in limited quantity.