Friday, March 29, 2024
General Agriculture

Time and Methods of Fertilizer Application on Crops

To achieve maximum benefit from fertilizers, it is most essential to apply them at the right time and in the place. The amount and timing of nutrient uptake depend on various factors, such as crop variety, planting date, crop rotation, soil, and weather conditions.

For good agricultural practices, the farmer chooses the timing and the quantity in such a way that as much as possible of the nutrients is used by the plants.

For optimum crop use efficiency and minimum potential for environmental pollution, the farmer must apply the nutrients as near to the time the crop needs them.

This is particularly important for mobile nutrients such as nitrogen, which can easily be leached out of the soil profile if they are not taken up by the plant roots.

1. Time of applying Nitrogen Fertilizers     

Since nitrogen is required throughout the growth period and nitrogenous fertilizers are lost through leaching, it is better not to apply too much nitrogen at one time.

The split application of nitrogen throughout the growing period will ensure greater efficiency and plants would not suffer from nitrogen deficiency

2. Time of applying Phosphorus Fertilizers 

This element is required in greater quantities during the early growth period and as all phosphorus fertilizers become available to growing plants slowly, it is always recommended that the entire quantity of phosphorus fertilizers be applied in a single dose before sowing or planting.

3. Time of applying Phosphorus Fertilizers

This element is absorbed right up to harvest stages but it becomes available slowly. It is therefore always advisable to apply the entire quantity of potassium as sowing time.

The Different Methods of Fertilizer Application

The method of application of fertilizers (organic manure or mineral fertilizers) is an essential component of good agriculture practices. A fast start continued nutrition is essential for sustained maximum profit.

It is important to place some of the fertilizers where it will intercept the roots of the young plant and to plant and to place the bulk of the nutrient deeper in the soil.

Nitrogen fertilizers are easily soluble in water and have mobility, so they can be applied on the soil surface.

Phosphorus fertilizers move slowly from the point of placement, it should be placed closer to the plant roots.

Phosphorus fertilizers should be placed so that they have minimal contact with soil particles and are close to plant roots to reduce phosphate fixation.

Potassium fertilizer moves slowly in the soil and should be applied close to the root zone.

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Based on these principles, the following methods are used to apply fertilizers.

1. Broadcasting Method

The fertilizer is spread over the entire soil surface to be fertilized to distribute the whole quantity of fertilizer evenly and uniformly and incorporate it in the plow layer.

It is used mostly on dense crops not planted in rows or in dense and on grassland. It is also used when fertilizer should be incorporated into the soil after application to be effective (phosphate fertilizers) or to avoid evaporation losses of nitrogen (urea, diammonium phosphate).

Incorporation through tilling or plowing-in is also recommended to increase the fertility level of the entire plough layer.

Whether the fertilizer is broadcast by hand or with fertilizer spreading equipment, the fertilizer should be as uniform as possible.

2. Row or Band Placement  

When relatively small amounts of fertilizer are to be applied, this refers to the application of fertilizers into the soil close to the seed or plant.

When fertilizers are placed in bands or pockets alongside or near the seed or plant, the roots of the young plants are assured of an adequate supply of nutrients, promoting rapid early growth.

This method of placement also reduces phosphorus and potassium fixation.

When seeds or plants are sown close together in a row, the fertilizer is put in a continuous band on one or both sides of the row.

This method of application is referred to as row placement and is used for potatoes, maize tobacco, cotton, sugarcane, etc.

Where crops are cultivated by hand and planted in hills, the recommended grams of fertilizer is placed in the row or planting hole, under, or beside the seed, and covered with soil, this is known as hill placement.

Great care has to be taken such that no fertilizer is placed either too close to the seed or the germinating plant to avoid toxicity.

3. Topdressing

 Top-dressing (broadcasting the fertilizer on standing crops) is mainly used for small and large grain crops and crops such as forage, wheat, and barley.

Topdressing of additional nitrogen is done when:

  I. a single application of the total nitrogen needed at sowing might lead to losses through leaching and run-off

ii. or where crops show a special need for nitrogen at certain stages of growth

Topdressing of potassium, which does not move in the soil to the same extent as nitrogen, might be recommended on the soils, i.e. applied before or at sowing or planting time (basal application), preferably in combination with potassium and part of the nitrogen.

Side dressing: This is also another form of top dressing where fertilizer is spread between the rows or around the plants.

Maize, cotton, sugarcane, trees, and other perennial crops are normally side-dressed.

4. Foliar application of fertilizer

Foliar application refers to the spraying of the leaves of growing plants with suitable fertilizer solutions.

It is used mainly to correct micronutrient deficiencies.

To minimize the risk of leaf scorch, the recommended concentration has to respect, and spraying should preferable by done cloudy days and in the early morning or late afternoon.

5. Direct application into the soil

Anhydrous ammonia (liquid fertilizer) and nitrogen solutions can be applied directly to the soil using specialized equipment.

If the material is applied about 10cm below the seed, there is very little plant injury or ammonium waste, and the ground is wet.

6. Application through irrigation water

Straight or mixed fertilizers which are easily soluble in water are allowed to dissolve in the irrigation stream.

The nutrients are thus carried into the soil in solution. The fertilizer most commonly applied through irrigation water is nitrogenous fertilizers.

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How to Determine Fertilizer Needs

To determine fertilizer needs for crops and soil in your locality you must know two things:

1. The status of nutrients in the soil.

2. How much of each nutrient is required to achieve the highest (or most profitable) yield?

There are several approaches to answering these questions;

1. Fertilizer recommendation of crops.

2. Nutrient hunger signs on growing crops (deficiency symptoms).

3. Soil tests or analyses to determine the fertilizer nutrients and the amount needed.

4. Plant or plant tissue test in the field.

5. Fertilizer field trails

Hunger signs in a plant (nutrient deficiency symptoms)

Time and Methods of Fertilizer Application on Crops

If plants do not get enough of a particular nutrient they need, the symptoms show in the general appearance as well as in the color of the plant.

The very typical symptom is: the nutrient-deficient plants are stunted, the leaves have a pale green color or a very dark bluish-green color, yellowish or have reddish spotting or striping. During the harvest, yields produced is reduced, and sometimes severely thereby affecting the crop farmer.

Nitrogen deficiency symptoms

1. Plants will have stunted growth

2. Loss of green color, discoloration of leaves from tip backward, older leaves brown.

3. Lower leaves may die prematurely while the top of the plant remains green

Phosphorus deficiency symptoms

1. Stunted growth.

2. Leaves turn dark green, purpling and browning from the tip backward.

3. Plants ripen slowly and remain green.

4. Fruits may be misshapen, and grain may be underfilled.

Potassium deficiency symptoms

1. Plants will have stunted growth.

2. Leaves show discoloration along the outer margin from tip to base.

3. Yellow or reddish outer edges of leaves, turning brownish or scorched and dead; wilted leaves

4. Lodging.

5. Tree leaves are yellowish or reddish and are pinched, cupped, or curved.

6. Fruit is small, may have lesions or be injured, and has poor storage and preservation quality.

Magnesium deficiency symptom

Yellowish discoloration between Greenleaf’s veins, followed by blotching and necrosis (death of tissue), starting at lower older leaves.

Sulfur deficiency symptom

1. The whole plant is yellowish (often mistaken as N deficiency).

2. Yellowish of upper leaves, even on the newest growth

3. Delayed crop maturity.

Calcium deficiency symptoms

1. Young leaves become yellowish to black in color and are curved or cupped (brown spot).

2. Plants appear to wilt.

3. Fruits may appear rotten.

4. Roots may malformed.

Boron deficiency symptoms

1. Leaves that are frequently misshapen and crinkled, thick and brittle, and with white, irregular spots between veins.

2. Crowing tips of buds die, with bushy growth near tips extension growth inhibited with shortened internodes.

3. Water-soaked, necrotic spots or cavities in beet and other root crops and the pith of stems.

4. Fruit small and poorly formed, often with corky nodules and lesions.

5. Low seed production due to incomplete fertilization.

Zinc deficiency symptoms

1. Stunted growth of leaves.

2. Fruits trees with typical shortened busy shoots.

3. Chlorotic stripes (white-bleached bands) between the veins in the lower part of the leaf.

4. In some cases, the color of the leaves is olive green or grayish-green (very similar to P deficiency).

Iron deficiency symptom

Young leaves with typical chlorosis between green veins running the length of the leaf (usually on calcareous soils).

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Soil Amendments

Soil amendments are the substance used for correcting the acidity or alkalinity of the soil. In high rainfall areas, there is considerable leaching of bases leading to the formation of acidic soil, while in low areas, saline and alkaline soils occur.

Soil reaction or soil pH

Soils vary considerably in the degree of acidity, alkalinity, or reaction.

The normal range is expressed in pH values as given in Table 3.1 below;

Table 3.1 Normal soil reaction range with corresponding Ph values

Range in soil reactionpH value
Extremely acidicBelow 4.5
Very strongly acidic4.5-5.0
Strongly acidic5.1-5.5
Medium acidic5.6-6.0
 Slightly acidic6.1-6.0
 Neutral6.6-7.3
 Mildly alkaline7.4-7.8
Moderately alkaline7.9-84
Strongly alkaline8.5-9.0
Very strongly alkaline9.1 and above

Liming of acidic soils

Liming as the term applies to agriculture is the addition is of any calcium or calcium and magnesium-containing compound to the soil for reducing acidity. For this purpose, calcium oxide, calcium hydroxide, calcium carbonate, calcium magnesium carbonate, and calcium silicate slag are used

Methods of applying lime

Lime should be applied before plough or applied on plowed land and then disked or mixed into the soil.

When large amounts of lime are required, it is best to apply the required amount in two or three splits rather than one large application.

On highly acidic soils, where 7-15 tonnes of lime are required per hectare, half the amount should be applied before ploughing, and the remaining half should be applied and disked after.

When the required amount of lime is less than 4-5 tonnes per hectare, the entire amount should be applied and disked in at once 8-10 days before sowing.

In summary, fertilizers are applied to crops to supply the nutrients that are not present in sufficient quantities n the soil. Year after year, the amount of nutrients that result in sustained maximum net returns.

This means that fertilizers are to be used most efficiently. To achieve maximum benefit from fertilizers, it is not most essential to apply them at the right time and in the right place.

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Agric4Profits

Benadine Nonye is an agricultural consultant and a writer with over 12 years of professional experience in the agriculture industry. - National Diploma in Agricultural Technology - Bachelor's Degree in Agricultural Science - Master's Degree in Science Education... Visit My Websites On: 1. Agric4Profits.com - Your Comprehensive Practical Agricultural Knowledge and Farmer’s Guide Website! 2. WealthinWastes.com - For Effective Environmental Management through Proper Waste Management and Recycling Practices! Join Me On: Twitter: @benadinenonye - Instagram: benadinenonye - LinkedIn: benadinenonye - YouTube: Agric4Profits TV and WealthInWastes TV - Pinterest: BenadineNonye4u - Facebook: BenadineNonye

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