METHODS OF FERTILIZER APPLICATION
The different methods of fertilizer application are as follows:
- It refers to spreading fertilizers uniformly all over the field.
- Suitable for crops with dense stand, the plant roots permeate the whole volume of the soil, large doses of fertilizers are applied and insoluble phosphatic fertilizers such as rock phosphate are used.
Broadcasting of fertilizers is of two types.
i) Broadcasting at sowing or planting (Basal application)
The main objectives of broadcasting the fertilizers at sowing time are to uniformly distribute the fertilizer over the entire field and to mix it with soil.
ii) Top dressing
It is the broadcasting of fertilizers particularly nitrogenous fertilizers in closely sown crops like paddy and wheat, with the objective of supplying nitrogen in readily available form to growing plants.
Disadvantages of broadcasting
The main disadvantages of application of fertilizers through broadcasting are:
i) Nutrients cannot be fully utilized by plant roots as they move laterally over long distances.
ii) The weed growth is stimulated all over the field.
iii) Nutrients are fixed in the soil as they come in contact with a large mass of soil.
- It refers to the placement of fertilizers in soil at a specific place with or without reference to the position of the seed.
- Placement of fertilizers is normally recommended when the quantity of fertilizers to apply is small, development of the root system is poor, soil have a low level of fertility and to apply phosphatic and potassic fertilizer.
The most common methods of placement are as follows:
i) Plough sole placement
- In this method, fertilizer is placed at the bottom of the plough furrow in a continuous band during the process of ploughing.
- Every band is covered as the next furrow is turned.
- This method is suitable for areas where soil becomes quite dry upto few cm below the soil surface and soils having a heavy clay pan just below the plough sole layer.
ii) Deep placement
It is the placement of ammoniacal nitrogenous fertilizers in the reduction zone of soil particularly in paddy fields, where ammoniacal nitrogen remains available to the crop. This method ensures better distribution of fertilizer in the root zone soil and prevents loss of nutrients by run-off.
iii) Localized placement
It refers to the application of fertilizers into the soil close to the seed or plant in order to supply the nutrients in adequate amounts to the roots of growing plants. The common methods to place fertilizers close to the seed or plant are as follows:
In this method, the fertilizer is applied at the time of sowing by means of a seed-cum-fertilizer drill. This places fertilizer and the seed in the same row but at different depths. Although this method has been found suitable for the application of phosphatic and potassic fertilizers in cereal crops, but sometimes germination of seeds and young plants may get damaged due to higher concentration of soluble salts.
b) Side dressing
It refers to the spread of fertilizer in between the rows and around the plants. The common methods of side-dressing are
- Placement of nitrogenous fertilizers by hand in between the rows of crops like maize, sugarcane, cotton etc., to apply additional doses of nitrogen to the growing crops and
- Placement of fertilizers around the trees like mango, apple, grapes, papaya etc.
c) Band placement
If refers to the placement of fertilizer in bands.
Band placement is of two types.
i) Hill placement
It is practiced for the application of fertilizers in orchards. In this method, fertilizers are placed close to the plant in bands on one or both sides of the plant. The length and depth of the band varies with the nature of the crop.
ii) Row placement
When the crops like sugarcane, potato, maize, cereals etc., are sown close together in rows, the fertilizer is applied in continuous bands on one or both sides of the row, which is known as row placement.
d) Pellet application
- It refers to the placement of nitrogenous fertilizer in the form of pellets 2.5 to 5 cm deep between the rows of the paddy crop.
- The fertilizer is mixed with the soil in the ratio of 1:10 and made small pellets of convenient size to deposit in the mud of paddy fields.
Advantages of placement of fertilizers
The main advantages are as follows:
i) When the fertilizer is placed, there is minimum contact between the soil and the fertilizer, and thus fixation of nutrients is greatly reduced.
ii) The weeds all over the field can not make use of the fertilizers.
iii) Residual response of fertilizers is usually higher.
iv) Utilization of fertilizers by the plants is higher.
v) Loss of nitrogen by leaching is reduced.
vi) Being immobile, phosphates are better utilized when placed.
Following are the common methods of applying liquid fertilizers
a) Starter solutions
It refers to the application of solution of N, P2O5 and K2O in the ratio of 1:2:1 and 1:1:2 to young plants at the time of transplanting, particularly for vegetables.
Starter solution helps in rapid establishment and quick growth of seedlings.
The disadvantages of starter solutions are
(i) Extra labour is required, and
(ii) the fixation of phosphate is higher.
b) Foliar application
- It refers to the spraying of fertilizer solutions containing one or more nutrients on the foliage of growing plants.
- Several nutrient elements are readily absorbed by leaves when they are dissolved in water and sprayed on them.
- The concentration of the spray solution has to be controlled, otherwise serious damage may result due to scorching of the leaves.
- Foliar application is effective for the application of minor nutrients like iron, copper, boron, zinc and manganese. Sometimes insecticides are also applied along with fertilizers.
c) Application through irrigation water (Fertigation)
- It refers to the application of water soluble fertilizers through irrigation water.
- The nutrients are thus carried into the soil in solution.
- Generally nitrogenous fertilizers are applied through irrigation water.
d) Injection into soil
- Liquid fertilizers for injection into the soil may be of either pressure or non-pressure types.
- Non-pressure solutions may be applied either on the surface or in furrows without appreciable loss of plant nutrients under most conditions.
- Anhydrous ammonia must be placed in narrow furrows at a depth of 12-15 cm and covered immediately to prevent loss of ammonia.
e) Aerial application.
In areas where ground application is not practicable, the fertilizer solutions are applied by aircraft particularly in hilly areas, in forest lands, in grass lands or in sugarcane fields etc.