Methods of fertilizer application has a significant influence on fertilizer recovery. The application method varies according to the spacing of crop, type of fertilizer material, time of application. A brief account of these points could be explained as follows.
Methods of Fertilizer Application
Solid fertilizer materials application method
Solid materials may be applied in the following ways:
A. Broadcasting
Even and uniform spreading of dry solid fertilizers by hand or spreader over the entire field before or after sowing of the crop is termed as broadcasting. Well-decomposed FYM (Farm yard manure), compost, oil cake, bone meal, urea, superphosphate, and lime are applied by this method.
Advantages
This method is easy, less time taking, cheap, and more convenient to the farmers. This method proves effective-
- When the crops have a dense stand.
- When the plant roots absorb nutrients from the whole volume of soil.
- When soil fertility rich.
- When using a large amount of material.
- When using potassic fertilizers on light soils.
Disadvantages
- It is not advantageous because it encourages weed growth all over the field.
- Most of the material remains on the soil surface and does not reach the root zone for uptake by plants.
- There is a more significant loss of fertilizer nutrients due to washing, run-off, volatilization.
- The recovery (extent of fertilizer used by plants) ranges between 25 to 45 percent or even less.
Types of broadcasting application methods:
1. Basal application
Spreading fertilizers before sowing or planting the crops and mixing them by cultivating the soil during seedbed preparation is termed as basal application through broadcasting.
Advantages
- Suitable for applying controlled/slow-release fertilizers.
- Suitable for applying bulky manures.
Disadvantage
Encourages early weed growth.
2. Topdressing and side dressing
Spreading of fertilizer in standing crops without considering the crop rows is termed as a top dressing. However, when the crop rows are taken into account, and the material is dropped on the ground surface near the crop rows, it is called side dressing.
Advantages
- Highly mobile fertilizers are top-dressed by split application.
- Side dressing reduces misuse of fertilizers in row crops.
Disadvantage
- Topdressing is not suitable for bulky manures.
B. Placement
It refers to applying fertilizers into the soil from where the crop roots can take them easily.
Advantages:
- Plants can use a maximum portion of the material.
- Losses through uptake by weeds, washing, run-off, volatilization could be eliminated to the greatest extent.
Disadvantage:
- Is not suitable for bulky manures.
The placement could be done in the following ways:
1. Plough sole placement
When the fertilizers are applied in open furrows at plow sole level while plowing, it is termed plow sole placement. Such furrows are covered immediately during the next run of the plow.
Advantages:
- This method is suitable when-
- In dry soil where there is moisture only in the sole plow layer.
- In problem soils where there is the problem of fixation.
Disadvantage:
- Is not suitable for bulky manures.
2. Deep placement
The method is adopted in the dryland condition where the fertilizers are placed deeper than the sole plow level; then, it is called deep placement.
Advantages
- Suitable for dry soil where there is a moisture deficit.
- Helps in root elongation.
- Eliminates various losses of nutrients from the soil.
- In wetland rice, a reduced form of N fertilizer (ammonium sulfate) is placed deep in the reduced layer to avoid denitrification.
Disadvantage
- Laborious and time-consuming.
3. Sub-soil placement
The method is termed sub-soil placement when placing fertilizers deeper than the seeding or planting depth and deeper than the previous two methods.
Advantages
- Suitable for dry soil where there is a moisture deficit.
- Helps in maximum root elongation.
- P and K fertilizers are placed in deeper layers by heavy machinery to avoid fixation in strongly acidic soils.
Disadvantage
- Laborious and time-consuming.
C. Localized placement
There is a distinction between placement and localized placement. The former refers to applying fertilizer into the soil without special reference to the location of the seed or plant. At the same time, the latter implies the application of fertilizer into the soil close to the seed or plant.
Advantages
Localized placement of fertilizers has many advantages over broadcasting methods of application such as. Relatively lesser quantity is required for the production of an ideal crop
- It suppresses weed growth.
- It reduces fertilizer losses.
- Placing fertilizers in the moist zone, where they remain available to plants for a more extended period.
- Fertilizers come in easy reach of crop roots.
- It increases fertilizer recovery and the response of crops to applied doses.
Disadvantages
- The method is very technical and needs special precautions.
- Besides, it is costly.
The method could be adopted in the following ways:
1. Contact placement/combine drilling
When placing fertilizer along with the seed, then it is called contact placement. It is done by using seed-cum-fertilizer drill. Sometimes fertilizer is drilled by implement, and seed is sown in the same furrow.
Advantage
Well-decomposed manure, ashes, and P and K fertilizers in small quantities are used along with seeds during sowing.
Disadvantage
Care must be taken so that seeds are not burnt by contact with fertilizers.
2. Band placement
It is a localized placement of fertilizers by the side of plants or seeds (about 5 cm apart). It may be of two types as the bands may be continuous or discontinuous:
i. Hill placement (discontinuous band)
In the hill, for widely spaced plants like cotton, castor, and cucurbits, fertilizers are placed on either side of plants along or across the row but not along the entire row. This method is also termed a discontinuous band application.
ii. Row placement (continuous band)
Along the entire rows of closely spaced crops like cereals, minor millets, potatoes, and tobacco, fertilizers are applied continuously at 2-2.5 cm depth. This method has a definite relationship of fertilizers with seedlings or seeds as the fertilizer is placed to the side of seedlings or seeds some distance away from them or at the seed level, above or below or by the side of the seed level. When the soil surface is dry, this method gives very promising results.
iii. Ring placement (continuous band)
Fertilizer is applied in a circle around an individual plant or hill base at a depth of about 2.5-5 cm.
3. Pocket/spot placement
When fertilizers are placed at a fixed spot with the help of a bamboo peg having a hole at the bottom in the case of very widely spaced crops, then the method is termed as pocket/spot placement method. Fertilizers are placed deeper into the pocket (dibble), and seeds are sown in the same pocket about 5 cm above the fertilizers.
Advantages
- Suitable for dry soil where there is a moisture deficit.
- Suitable for wide-spaced crops like cotton, castor, cassava, cucurbits, and chili.
Disadvantage
- Care must be taken so that seeds are not burnt by contact with fertilizers.
- Laborious and time-consuming.
4. Pellet placement
This method is adopted, especially in deepwater rice cultivation. It is not easy to apply fertilizers in typical methods as the fertilizer granules get dissolved in water before reaching ground level. In this method, fertilizers (especially nitrogenous ones) are mixed with clay soil in the ratio of one part of fertilizer into 10-15 parts of soil. The fertilizer is well-mixed with soil after slight moistening, filled in gunny bags, and stored for two to three days. Small mud bolls are prepared, and these boll or pellets are dropped near the crop rows in rice Jr jute under deep water conditions.
Liquid fertilizer application method
The use of liquid fertilizers is not a very common practice, but this is the most common method in advanced countries. It is the most suitable method under dryland agriculture and in areas prone to erosion problems. Liquid fertilizers may be applied in the following ways:
1. Use of starter solution
Starter solutions usually contain N, P, K, in 1: 2: 1 or 1: 1: 2. This method is used for transplanted crops in place of irrigation water, and this solution is applied just to wet the field so that the seedlings may establish quickly.
Advantages
- It serves as irrigation water as well as a nutrient solution for the crops.
- Suitable for dipping the seedling roots and soaking seeds or spraying to encourage early rooting and crop establishment.
Disadvantage
- Requires careful attention to maintain the proper concentration of the solution.
2. Application through irrigation water
The required quantity of fertilizer material is dissolved in irrigation water and can be used in surface, sprinkler, or drip irrigation systems.
Advantage
- The concentrated fertilizer solution may be dripped in the channel of irrigation water while irrigating the crop.
Disadvantage
- If the crop is to be given surface irrigation as flooding, excess water may lead to physiological problems in crops.
3. Nutrient injection method/direct application to soil
In the USA and some other countries, farmers inject anhydrous ammonia into the soil at a depth of about 20-25 cm and a pressure of about 200 pounds per square inch.
Advantages
- Anhydrous ammonia is the cheapest source of nitrogen because of its lower unit value.
- Injecting hormonal solutions and some micronutrient solutions in the phloem region of the fruit trees is also becoming a distinct possibility in correcting the nutrient deficiency.
Disadvantage
- For this method, the soil should have fine tilth, enough moisture so that nitrogen loss in the form of ammonia does not occur.
4. Foliar spraying of nutrient solutions
In this method of fertilizer application, urea, micronutrients, and other required materials are dissolved in water, filtered, and sprayed over the crop foliage with the help of a suitable sprayer.
Advantages
- This method is preferred over other methods because it needs a minimal quantity of materials.
- The crop plants respond within 24 hours of application.
- Soil reaction, topography, and soil textures have no adverse effect on the soil’s nutrient availability and fertility status.
- Possible to apply almost all nutrients by this method.
Disadvantage
- Non-uniform spraying and improper concentration of the solution may lead to hazardous effects on the crop, and the entire plant population may get devastated.
- A high concentration of the solution may cause the burning of foliage.