The Fertilizer Placement methods to use depends on the crop, cropping system, nature of fertilizer materials, labor cost among others.
1. Broadcast
The fertilizer is spread uniformly over the surface of the land before or after planting. It may or may not be worked into the soil.
The slowly dissolving fertilizers, such as P, should be worked into the soil. Urea should be worked into the soil because it is volatile especially if soil is dry and temperature is high.
Others such as (HN 4 )SO 4 ) and KCl may be applied on the surfaces but run-off may occur on sloppy surfaces where intensity of rainfall may be greater than infiltration rate. This method is suitable for those crops whose seeds are usually broadcast.
2. Ring Application
For plants that are far placed apart such as tree crops-oil palm, cocoa, rubber, plantain, etc.
3. Row, Band, or Side-Dressing
Usually applied to the side(s) in a band and usually 5 to 10cm to the side and about 5cm deep. Machines are designed to achieve this.
Row application is used for crops grown in rows at close spacing such as maize, cowpea, soya beans, tomato, cotton and potato. Band placement minimizes fertilizer-soil contact and reduces P-and K-fixation.
4. Spot Application
Similar to ring application, but in addition, holes are made in a ring form round the crop so as to make the fertilizer go down deep into the soil. It is used to apply fertilizer to deep-rooted permanent crops such as orange and palms.
5. Top-Dressing
The fertilizer is applied to the crop after emergence. Top-dressing usually refers to broadcast application on crops such as small grain or forage as a second dose on the soil surface close to the plants when they are 3-4 weeks old. Nitrogen fertilizers are usually applied with this method.
6. Foliar Application
Particularly used for micro-nutrients such as Fe, Mn, Cu, Zn, Mo, Bo and Cl; leaves are able to take up directly the small amounts needed by plants when applied in liquid form.
Concentration of nutrient in solution is less than 1% to avoid leaf burn. This method is used for deep rooted trees whose roots grow into sub-soil beyond fertilizer zone. Foliar spraying avoids problem of nutrient fixation when applied to the soil.
Read Also: 7 Most Essential Micronutrients Fertilizer in Crop Production: The Key to Higher Crop Yield
Fertilizer Efficiency
The amount of fertilizer nutrient absorbed by the plant compared to the quantity of the fertilizer nutrient added to the soil gives the efficiency (Fe). It is expressed in percentages. Fe = Nutrient in plant x 100 Nutrient added.
It is assumed that plants do not absorb excess nutrient, but this is not so, since plants will continue to absorb nutrients for as much at it is available; this is known as Luxury consumption by plants.
The second assumption is that all nutrients absorbed are necessary for increased yield. Nitrogen, phosphorus and potassium have about 30-70%, 5-30% and 50-80% of their added nutrient utilized by plants respectively.
Since maximum efficiency is difficult to achieve for reasons of management changes, profitability and environmental factors, the goal of any farmer is to achieve optimum fertilizer efficiency, which gives best results for the expenditures of money, time and equipment.
