Complete guide for applying fertilizer to the soil by different methods and applications.
In order to get maximum benefit from manures and fertilizers, they should not only be applied in proper times and in right manner, but any other aspects should also be given careful consideration. Different soils react differently with fertilizer application. Similarly, the N, P, K requirements of different crops are different and even for a single crop the nutrient requirements are not the same at different stages of growth.
Fertilizers are applied by different methods mainly for three purposes:
i. To make the nutrients easily available to crops
ii. To reduce fertilizer losses
iii. For ease of application
The time and method of fertilizer application vary in relation to-
(a) The nature of fertilizer
(b) Soil type
(c) The differences in nutrient requirement and nature of field crops
Application of Fertilizers in Solid Form:
It includes the methods like:
1. Broadcasting:
Even and uniform spreading of manure or fertilizers by hand over the entire surface of field while cultivation or after the seed is sown in standing crop, termed as broadcasting.
Depending upon the time of fertilizer application, there are two types of broadcasting:
(i) Broadcasting at planting
(ii) Top dressing
(i) Broadcasting at Planting:
Broadcasting of manure and fertilizers is done at planting or sowing of the crops with the following objectives:
a. To distribute the fertilizer evenly and to incorporate it with part of or throughout the plough layer.
b. To apply larger quantities that can be safely applied at the time of planting/sowing with a seed-cum-fertilizer driller.
It is adopted with the following conditions:
i. When N-oust fertilizers like ammonium sulphate, ammonium sulphate nitrate, concentrated organic manures, are to be applied to the soil deficient in N or where N is exhausted by previous crops like fodder jowar, fodder maize.
ii. When citrate soluble P-tic fertilizers like basic slag and dia-calcium phosphate, are to be applied to moderately acid to strongly acid soils.
iii. When K-ssic fertilizers like muriate of potash and potassium sulphate are to be applied in potash deficient soil.
(ii) Top Dressing:
Spreading or broadcasting of fertilizers in the standing crop (after emergence of crop) is known as top dressing. Generally, NO3 – N fertilizers are top dressed to the closely spaced crops like wheat, paddy, e.g., sodium nitrate, ammonium nitrate and urea, so as to supply N in readily available from the growing plants.
The term side dressing refers to the fertilizer placed beside the rows of a crop (widely spaced) like maize or cotton. Care must be taken in top dressing that the fertilizer is not applied when the leaves are wet or it may burn or scorch the leaves.
The top dressing of P and K is ordinarily done only on pasture lands which occupy the land for several years.
In some countries, aeroplanes are used for fertilizer application in hill terrains where it is difficult to transport fertilizers and where large amount are to be applied because of severe deficiency and under following situations:
(i) Where very small quantities of fertilizers are needed over large areas, e.g., micronutrients.
(ii) When high analysis materials are applied.
(iii) When fertilizer application may be combined with insect control or some other air operation.
(iv) As a labour and time saving device.
2. Placement:
In this, the fertilizers are placed in the soil irrespective of the position of seed, seedling or growing plant before or after sowing of the crops.
It includes:
(i) Plough Sole Placement:
The fertilizer is placed in a continuous band on the bottom of the furrow during the process of ploughing. Each band is covered as the next furrow is turned.
By this method, fertilizer is placed in moist soil where it can become more available to growing plants during dry seasons.
It results in less fixation of P and K, then that which occurs normally when fertilizers are broadcast over the entire soil surface.
(ii) Deep Placement or Sub-Surface Placement:
In this method, fertilizers like ammonium sulphate and urea, is placed in the reduction zone as in paddy fields, where it remains in ammonia form and is available to the crop during the active vegetative period. It ensures better distribution in the root zone, and prevents any loss by surface runoff.
Methods of Placement:
(i) Contact Placement or Combined Drilling or Drill Placement:
It refers to the drilling of seed and fertilizer together while sowing. It places the seed and small quantities of fertilizers in the same row. This is found useful in cereal crops, cotton and grasses but not for pulses and legumes. This may affect the germination of the seed, particularly in legumes due to excessive concentration of soluble salts.
(ii) Band Placement:
In this, fertilizer is placed in bands which may be continuous or discontinuous to the side of seedling, some distances away from it and either at level with the seed, above the seed level or below the seed level.
There are two types of band placement:
a. Hill Placement:
When the plants are spaced 3 ft. or more on both sides, fertilizers are placed close to the plant in bands son one or both sides of the plants. The length and depth of the band and its distance from plant varies with the crop and the amount of fertilizer as in cotton.
b. Row Placement:
When the seeds or plants are sown close together in a row, the fertilizer is put in continuous band on one or both sides of the row by hand or a seed drill.
(iii) Pellet Application:
In this method, fertilizer (N-ous fertilizers) is applied in the form of pellets 2.5-5.0 cm deep between the rows of paddy crop. Fertilizer is mixed with soil in the ratio of 1:10 and make into dough. Small pellets of a convenient size are then made and deposited in the soft mud of paddy fields. It increases the efficiency of N-ous fertilizers.
(iv) Side Dressing:
Fertilizers are spread in between the rows or around the plants.
It includes:
a. Application of N-ous fertilizers in between the rows by hand to broad row crops like maize, sugarcane, tobacco, cereals which is done to supply additional doses of N to the growing crop.
b. Application of mixed or straight fertilizer around the base of the fruit trees and done once, twice or thrice in a year depending upon age.
Application of Liquid Fertilizers:
(i) Starter Solutions:
Solutions of fertilizers, generally consisting of N, P2O5, K2O in the ratio of 1:2:1 and 1:1:2 are applied to young vegetable plants at the time of transplanting. It helps in the rapid establishment of seedlings and quick early growth.
Advantages:
a. The nutrients reach the plant roots immediately.
b. The solution is sufficiently diluted, so that it does not inhibit growth.
Disadvantages:
a. Extra labour is necessary.
b. Fixation of phosphate is greater.
(ii) Foliar Application:
It refers to the spraying of leaves of growing plants with suitable fertilizers solutions. These solutions may be prepared in a low concentration to supply any one plant nutrients.
It is preferable to soil application when:
a. The soil conditions or a competitive crop makes nutrients from soil dressing unavailable, like late application of N to crops raised under Rainfed condition.
b. An accurately time response to fertilizers is required, e.g., change in the reason.
Advantages:
a. It is the best way to grow plants in places where there is not enough water.
b. It produces an almost immediate effect on the plants.
Disadvantages:
a. Leaf bum on scorching may occur, if strong solutions used.
b. Small quantities of nutrients can be applied in one single spray due to low concentrations.
c. Several applications are needed for moderate to high fertilizer doses.
d. Costly method than soil application.
(iii) Direct Application to the Soil:
With the help of special equipment, anhydrous ammonia (a liquid under high pressure up to 200 PSI or more) and N solutions are directly applied to the soil. It allows direct utilization of the cheapest N source. Plant injury or wastage of ammonia is very little, if the material is applied 10 cm below the seed. Otherwise, the N from ammonia will be lost. If requires moisture content at field capacity and good soil tilth.
(iv) Application through Irrigation Water:
Straight and mixed fertilizers containing N, P and K easily soluble in water, are allowed to dissolve in the irrigation stream. The nutrients are thus carried in solutions. This saves the application cost and allows the utilization of relatively in expensive soluble fertilizers, like N-ous fertilizers.