In order to get maximum benefit from your manure and fertilizer, you should apply them in the proper time and the right manner. That said, there are several other aspects which 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 a crop the nutrient requirements are not the same at different stages of growth. The aspects that require consideration in fertilizer application are listed below:
1. Availability of nutrients in manures and fertilizers.
2. Nutrient requirements of crops at different stages of crop growth.
3. Time of application.
4. Methods of application, placement of fertilizers.
5. Foliar application.
6. Crop response to fertilizers application and interaction of N, P, and K.
7. Residual effect of manures and fertilizers.
8. Crop response to different nutrient carrier.
9. Unit cost of nutrients and economics of manuring.
Fertilizers are applied by different methods mainly for 3 purposes:
1. To make the nutrients easily available to crops,
2. To reduce fertilizer losses and
3. For ease of application.
The time and method of fertilizer application vary in relation to
1) The nature of fertilizer.
2) Soil type and
3) The differences in nutrient requirement and nature of field crops.
Application of fertilizers in solid form: It includes the methods like,
I) 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 broad casting. Depending upon the time of fertilizer application, there are two types of broadcasting:
A) Broadcasting at planting and
B) Top dressing.
A) Broadcasting at planting: Broadcasting of manure and fertilizers is done at planting or sowing of the crops with the following objectives:
1) To distribute the fertilizer evenly and to incorporate it with part of, or throughout the plough layer and
2) 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 condition:
1) When N-ous fertilizers like amm. Sulphate, Amm. 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, F. maize.
2) When citrate soluble P-tic fertilizers like basic slag and dia-calcium phosphate, are to be applied to moderately acid to strongly acid soils.
3) When K-ssic fertilizers like Muriate of potash and potassium sulphate are to be applied in potash deficient soil.
B) 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, Amm. 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, aero planes 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:
1. Where very small quantities of fertilizers are needed over large areas. E.g.: Micro nutrients.
2. When high analysis materials are applied.
3. When fertilizer application may be combined with insect control or some other air operation and
4. As a labour and time saving device.
II) 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:
1. 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 & K than that which occurs normally when fertilizers are broadcast over the entire soil surface.
2. Deep placement or sub-surface placement: In this method, fertilizers like Amm. 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. It is followed in different ways, depending upon local cultivation practices such as:
i) Irrigated tracts: The fertilizer is applied under the plough furrow in the dry soil before flooding the land and making it ready for transplanting.
ii) Less water condition: Fertilizer is broadcasted before puddling which places it deep into the reduction zone.
iii) Sub – soil placement: This refers to the placement of fertilizers in the sub-soil with the help of heavy power machinery. It is followed in humid and sub-humid regions where many sub-soils are strongly acid, due to which the level of available plant nutrients is extremely low. P-tic and K-ssic fertilizers are applied by this method in these regions for better root development.
III) Localized placement: It refers to the application of fertilizers into the soil close to the seed or plant. It is usually employed when relatively small quantities of fertilizers are to be applied. It includes methods like:
i) The roots of the young plant are assured of an adequate supply of nutrients,
ii) Promotes a rapid early growth,
iii) Make early Intercultivation possible for better weed control,
iv) Reduces fixation of P & K.
1. 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.
2. 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: It includes hill and row 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 one or both sides of the row by hand or a seed drill. It is practiced for sugarcane, potato, maize, tobacco, cereals and vegetable crops.
Higher rates of fertilizers are possible with row placement than hill placement. For applying small amount of fertilizers, hill placement is usually most effective.
3. 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.
4. Side dressing: Fertilizers are spread in between the rows or around the plants. It includes i) application of N-ous fertilizers in between the rows by hand to broad row crops like maize, S.cane tobacco, cereals which is done to supply additional doses of N to the growing crop. ii) 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.