After reading this article you will learn about Fertilizers:- 1. Methods of Fertilizer Application 2. Time of Fertilizer Application 3. Factors Affecting Optimum Fertilizer Dose.
Methods of Fertilizer Application:
Various methods are used for fertilizer application.
The methods are classified as follows:
(A) Application of Fertilizers in Solid Form:
Evenly spreading the dry fertilizer over the entire field and incorporating by cultivation is termed as broadcasting.
(i) Basal application:
Evenly spreading of solid fertilizers over the entire filed before or at sowing or planting is called basal dressing.
(ii) Top dressing:
The broadcasting of the fertilizer on closely sown standing crops is called top dressing. Generally, nitrogenous fertilizers are used for top dressing. N- fertilizer should not apply on wet leaves.
(i) Plough sole placement. Fertilizer is placed in a continuous band on the bottom of the furrow during the process of ploughing.
(ii) Deep Placement:
Usually nitrogenous fertilizer (urea) is placed in reduction zone (deep in the soil), where it remains in ammonicalform and is available to the crop slowly.
(iii) Sub-soil placement:
Fertilizers like phosphate and potash are placed in subsoil. This method is recommended in humid and semi-humid regions where many subsoils are strongly acidic.
III. Localized Placement:
Fertilizers are applied close to the seed or plant.
(i) Drill Placement or Contact Placement:
Fertilizers are drilled along with the seed, using suitable equipment (e.g., fertilizer drills or seed-cum-fertilizer drill).
(ii) Band Placement:
This is a system of localized placement of fertilizer in the hill or along the row of crops.
(iii) Side Dressing:
The fertilizer applied after the crop has been seeded in spaced rows. This may be done either as a continuous band near the crop row or dibbled in between the plants. Side dressing is a very common practice in long duration crops such as sugarcane.
(iv) Spot Placement:
Sometimes the fertilizer is placed in between the plants in pinches at the base of each pair of plants.
(v) Ring Placement:
In this method, fertilizers are applied around the plants in rign (basin).
(B) Application of Fertilizers in Liquid Form:
1. Foliar Application:
Some fertilizers in liquid form can be applied by spraying directly on the leaves of crop plants. Several nutrient elements are readily absorbed by leaves. Urea (N- fertilizer) and micronutrients like zinc sulphate, magnesium sulphate etc., are most common. Since urea is an organic form of nitrogen, it causes the least injury. It can be sprayed at the rate of 2-4 per cent. Three kilograms of urea in 500 litres of water has been reported safe.
(1) This method may be suitable where soil application of fertilizers are not possible. For example, hills, sandy soil etc.
(2) Micro-nutrients are required in small quantities and their solution are not strong. Their application by foliar spray has given better results compared to soil application.
(i) Plant nutrients are absorbed through the leaves only in limited quantities,
(ii) In several cases of plant nutrient deficiencies, it will generally, take more than one spray application to correct the deficiency,
(iii) Strong solution may cause leaf injury,
(iv) It is a costly method.
Principles involved in selecting the Correct Method of Fertilizer Application:
1. Nitrogen fertilizer is easily soluble in water and moves rapidly in all directions from place of application. Nitrogen applied in soil surface reach the plant root easily and rapidly. As such, these fertilizers are broadcast on the soil surface just before sowing.
2. Leaching and volatilization loss is very high in nitrogenous fertilizers. So that N- fertilizers are suitable for top dressing and side dressing.
3. To reduce the fixation of phosphate, phosphatic fertilizers should be so placed that they come into minimum contact with the soil particles and are close to the plant roots. In other words, localized placement of phosphatic fertilizers near the seed or seedling roots should be practiced.
4. Phosphatic fertilizers are not much suitable for top dressing.
Time of Fertilizer Application:
Principles governing selection of proper time for application of fertilizers are:
1. Nitrogen is required throughout the crop growth. Nitrogen is taken up by the plant slowly in the beginning, rapidly during the grand growth period and again slowly as it nears maturity.
2. Nitrogen is lost easily through leaching. Therefore, it is better not to apply too much nitrogen fertilizer at one time, but to apply in split doses throughout the growth period.
3. Phosphorus is required during the early root development and early plant growth. As such, crop plants utilize 2/3rd of the total requirement of phosphorus when the plants accumulate l/3rd of their dry weight.
4. All phosphatic fertilizers release phosphorus for plant growth slowly. As such, it is always recommended that the entire quantity of phosphatic fertilizers should be applied before sowing or planting.
5. Potash behaves partly like nitrogen and partly like phosphorus. From the point of view of the rate of absorption, it is like nitrogen, being absorbed, up to the harvesting stage. But potash fertilizer like phosphate becomes available slowly. As such, it is always advisable to apply the entire quantity of potash at sowing time. Leaching of potash is greater in sandy soils. This means split application of potash is desirable in sandy soils.
Factors Affecting Optimum Fertilizer Dose:
The factors which affect the optimum fertilizer dose are:
1. Initial Soil Fertility. Plants growing on soils high in available plant nutrients responds little to application of fertilizers. This soil requires little dose of fertilizers.
2. Soil pH. In neutral soil (pH 7.0) responses of fertilizers is maximum. In acidic, saline and alkaline soils availability of fertilizers is reduced, thus, higher application is needed.
3. Soil Texture. Sandy soil requires greater amount of fertilizer in comparison to a clayey soil.
4. Soil Erosion. Eroded soil requires heavier fertilizer dose.
5. Rainfall. There is high requirement of fertilizer in the areas of high rainfall.
6. Previous Crop Raised. If an exhaustive crop like maize is taken during the kharif season, the wheat crop to be sown during rabi season requires a higher dose of nitrogen.
7. Intensity of Cropping. Higher the cropping intensity, higher removal of nutrients.
8. Sowing Period. If the crop is sown late, dose should be increased.
9. Irrigated Area. Fertilizer dose should be more in comparison to un-irrigated areas.