Frequently Asked Questions About Fertilizers (FAQs)

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FAQ’s on Fertilizers / Frequently Asked Questions About Fertilizers

The following Frequently Asked Questions About Fertilizers are useful if you are into agriculture, farming or gardening. These can also be a reference for exams, interviews of agriculture jobs.

  1. What are fertilizers and how do you read them?

Fertilizers are materials or compounds that provide nutrients to the plants for growth and development that are deficient in the soil. The label on the fertilizers indicates three bold numbers, i.e. 10.10.10 or 10-10-10 which means that the first number indicates the amount of nitrogen, the second number is the amount of phosphate and the third number is the amount of potash. The total number on the label represents the primary nutrients present in the fertilizer. This is a national standard of grading fertilizers. 10 means that the percentage of nutrient present in the fertilizer.

  1. What are different types of fertilizers?

Fertilizers are broadly divided into two major categories or types, organic and inorganic fertilizers. Organic fertilizers are cow manure, green manure compost, etc. whereas inorganic compounds are chemical-based fertilizers available in powdered or granular form like the NPK fertilizers.

  1. What are natural fertilizers and name some examples of natural fertilizers?

Natural fertilizers also called organic fertilizers are the one that is derived from animal matter, human excreta, vegetable matter (compost and crop residue). Some compounds or substances are naturally formed on earth like peat, manure, slurry, guano etc. and are also considered organic. They contain or supply the same nutrients present in chemical compounds, but the composition is different and cannot be altered.

  1. What is the best fertilizer for flowering plants?

Flowering plants need fertilizers that are rich in the primary elements: nitrogen, phosphorous and potassium, so as to help the plants develop healthy foliage, root system and encourage flower and fruit formation respectively. Though all the elements are required, it should be clearly noticed that the fertilizers for flower plants exclusively have the largest percentage of phosphorous to ensure root formation and healthy flowering.

Foliar fertilizers are a type of liquid nutrients sprayed on the plants such that the leaves of the plants absorb nutrients, but it should be understood that not all plants need it and only some plants with certain nutrient deficiency absorb the foliar fertilizers quickly.

  1. What type of fertilizers do farmers use and why?

Farmers use different fertilizers based on the plant they are growing because each plant or crop has a varying level of nutrient requirement and understanding the differences in the needs of plants is very important while fertilizing the crops. The major type of fertilizer used by most of farmers is the NPK type chemical-based fertilizer. Other than this, farmers also use organic or natural fertilizers if they are growing organic food or if the plant exclusively needs organic elements.

It is very clearly known that after years of cultivation on the same land or due to adverse weather conditions, the fertility of the soil is lost, i.e. the essential nutrients required by the crops are not supplied adequately by the soil. So under such circumstances to help the plants have healthy growth and productivity, it is important to supplement the soil with deficient nutrients which is why farmers use fertilizers.

  1. What are some examples of organic fertilizers?

Organic fertilizers used for vegetable gardens or farms are compost, compost tea, herbivore manure, fish and seaweed emulsions, and vermicompost. Some other natural organic fertilizers available are alfalfa meal, bat guano, corn gluten meal, chicken manure, green sand, soybean meal, blood meal, bone meal, feather meal and fish meal.

  1. What are the advantages of fertilizers?

Advantages of using fertilizers are:

  • They are easy to store and move because of the lightweight.
  • They are nutrient specific and address the deficiency exactly.
  • Most of them are water-soluble which makes absorption quick and easy.
  • Have a rapid action on plants.
  • Increase the productivity of the crops.
  • Can be used only when needed at different stages of plant growth.
  1. What are the disadvantages of fertilizers?

Some disadvantages of chemical fertilizers when used in excess are:

  • Increases nitrate levels in soil and water which leads to eutrophication.
  • Prolonged use of fertilizers can imbalance the pH level of the soil.
  • Can disturb the conducting and water holding capacity of the soil.
  • Do not help in sustaining the soil properties.
  1. What are types of inorganic fertilizers and name some examples of inorganic fertilizers?

Some basic examples of inorganic fertilizers are compounds containing nitrogen, potassium, phosphorous such as ammonium nitrate, potassium nitrate, calcium nitrate, urea, potassium sulfate, potassium nitrate, Muriate of potash, rock phosphate, superphosphate etc. Inorganic fertilizers are available in two forms: single nutrient or multi-nutrient type. The multi-nutrient variety contains basic elements NPK and secondary elements or micronutrients like calcium, magnesium, boron, manganese, etc. There are also other types of inorganic fertilizers called the slow-release formulas, which break down slowly and release the nutrients without causing much damage to the plants.

  1. What are artificial fertilizers and their disadvantages?

Artificial fertilizers are also called synthetic fertilizers or inorganic fertilizers and are man-made combinations of chemicals and compounds to address the requirements of the plants. The disadvantages are similar to inorganic fertilizers (refer to Q-8).

  1. How does fertilizer work?

Each element in the fertilizer works for the development and functioning of different parts of the plant. Fertilizers also work to improve the soil condition by helping it retain water and allowing possible airflow to the roots. Nitrogen in the fertilizer helps the plant to produce stems, flowers and fruits; it also keeps the foliage green in colour. Phosphorous in the fertilizer helps produce oil and starch content in the produce; it keeps the root system strong. Potassium helps the plant to fight plant diseases and build the protein content in the plant.

  1. Are chemical fertilizers harmful and what are the harmful effects of chemical fertilizers?

Chemical fertilizers are substances that have always added nutrients to the soil and increased the fertility of the soil, but sometimes when overused they are harmful to the soil because they harden the soil, decrease fertility, pollute the air and water and release excess greenhouse gases. Too much alkalinity in the soil due to fertilizers makes the soil barren. Other negative effects of fertilizers are root burn, plant dehydration, soil acidification and groundwater contamination.

  1. How much fertilizer should one use on plants?

It is important to test the soil to know the amount of fertilizer that should be applied to the soil, but if the soil has not been tested the general recommendation of fertilizer use should be 2 to 3 pounds of NPK for every 100 sq ft of area. For example, if the area is 30 ft long and the rows are 3 ft apart then the application of fertilizer should be 2 pounds for sandy soil and 3 pounds for clay soil.

  1. How is fertilizer applied?

Fertilizers are applied to the soil or plants in four different ways:

Broadcast way: generally used for flower beds, trees and vegetable gardens. The application of fertilizers before planting the crops is called the broadcasting method. If the fertilizers are incorporated into the soil after planting then it is called top dressing.

Starter solution: fertilizers that are soluble in the water are sprayed or sprinkled on young plants at the time of transplanting is called a starter solution.

Side dressing: applying the fertilizer around the plant in a band of 2 inches to the side of the plant with a depth of 2 inches during the growing period is called side dressing.

Deep soil application: fertilizers are applied in bands below the furrows or applied at the top of the soil and harrowed to work the fertilizer into the soil.

  1. When should fertilizers be applied to plants?

Every kind of plant species has a different time for fertilizing. It has been observed that plants need varying amounts of nutrients at different rates during different stages of growth. Some fertilizers are applied in split doses to avoid salt damage to the crops and improve germination. Tow important factors that help us decide the time and frequency of fertilizer application are Cation Exchange Capacity (CEC) and soil texture.

Nitrogen fertilizer should not be applied before it is used up by the plants, so the basic technique of applying nitrogen is in split doses such that it reduces the risk of nitrogen loss and improves efficiency.

Similarly, phosphorous fertilizer is very slowly consumed by the plants and it remains on the top of the soil due to which there is a possible risk of loss by runoff and erosion. Phosphorous fertilizer should never be applied just before the rainy season.

Other than these specifications there are a few guidelines for fertilizing flowering plants:

  • Annual plants need fertilization of the soil during bed preparation.
  • Perennial plants or ornamental plants need fertilizers during the spring.
  • Plants need fertilizers during bud formation.
  • Fertilizing the plants should be avoided during fall and winter.
  1. Which fertilizer makes plants grow faster?

Fertilizers that stimulate faster growth of plants should contain little nitrogen and higher levels of phosphorous and potassium i.e. NPK (3-20-20). This ratio of nutrients helps the growth of roots and leads to stem development.

  1. What kind of fertilizer makes flowers bloom?

The fertilizers available in the market have a predefined quantity of NPK labelled on the pack, which makes it easy for one to understand what to choose for flowering plants. It’s already discussed that flowering needs a higher amount of phosphorous in the soil so choosing a fertilizer marked as 12-12-12 or 26-3-3 would not be appropriate because high nitrogen can burn the plants. So, the recommended fertilizer for flowering or better bloom is 5-30-5. Some bloom fertilizers also contain little iron, manganese and zinc.

  1. How much do farmers spend on fertilizers?

The price spent on fertilizers largely depends on the type of plant or crop being cultivated. Some plants consume fertilizers at a very fast rate and reapplication would be needed. For farmers cultivating crops on a commercial scale, fertilizers are available by cooperatives at reasonable rates and each type of fertilizer has a different rate. For example NPK-I (10: 26:26) type of fertilizer cost around Rs 25,600 per MT, NPK-II (12: 36: 16) costs Rs 25,800/MT, NP (20-20-0-13) costs Rs 20,300/MT, DAP (18-46-00) costs Rs 26,800/MT and neem coated urea costs Rs 5922/45 kg.

  1. What is fertilizer burn and do plants recover from fertilizer burn?

The burning of leaves, i.e. the leaves turn brown on the edges is a condition in plants when they are over-fertilized. Fertilizers generally contain salts that draw water or moisture from the plants and cause damage. If fertilizers are applied in excess, the symptoms of burning show up immediately. If the fertilizer is a slow-release type, then it takes a couple of weeks to show symptoms of the burn.

It is obvious that the burn could be prevented by certain methods like:

  • Fertilizer with only required quantity of fertilizer.
  • A slow-release type of fertilizer should be preferred.
  • Fertilizing plants with compost reduces the risk of burn.
  1. Why is too much fertilizer bad for plant osmosis?

Fertilizers contain salt and when salts are applied to soil, they don’t dissolve in water and plants only use the water for survival because the ability of the plant to pass water in and out of the roots should be lower than that of the water holding capacity of the soil. To adjust to the salinity plants must absorb and accumulate salts inside the plant so that the quantity of salt present inside the plant is higher and the water intake is normal again. This process slows down the growth of plants. Salts also block the enzyme systems and biochemical pathways of the plant. Salts injure the roots of the plant and interfere with the water intake process causing wilt.

  1. Why is too much fertilizer bad for plants?

Too much fertilizer use causes stress in the plants and weakens them, which ultimately makes the plants susceptible to diseases and insect attacks. Much severe problem due to over-fertilization is iron chlorosis.

  1. What are signs of over-fertilizing?

The symptoms of too much fertilizer application can be found by the following:

  • Yellowing of leaves
  • Wilting
  • Brown colouration of leaf margins and tips
  • Rotting of roots
  • Leaf drop
  • Very slow plant growth
  • The hard crust of fertilizer on the surface of the soil
  • Death of seedlings
  1. How long does it take granular fertilizer to work on plants?

The granular form of fertilizer is dissolved in water before application and it takes approximately 2 to 5 days to activate and show results in the plants.

  1. What is the difference between manure and fertilizer?

The major differences between fertilizer and manure are:

  • Fertilizers are man-made and are prepared in factories whereas manure is a combination of inorganic and organic substances.
  • Fertilizer can provide the exact amount of nutrients to the plants, but manure has a mixture of all nutrients because they contain organic elements which occur naturally in nature.
  • Fertilizers have high nutrient concentration and manure has a low concentration of nutrients.
  • Humus is provided by manure and not by fertilizers.
  1. What does DAP fertilizer contain?

Diammonium phosphate (DAP) is found in granulated form. The size of the granules is 5.5 mm and they are white, grey or black in colour. It contains 18% of the nitrogen in the form of ammonia and 46% phosphorous in the form of ammonium phosphate. It is commonly used for field crops and vegetables.

  1. What is the function of urea fertilizer and what are its advantages?

Urea is considered the king of fertilizers and the two main reasons for this is it contains 46% of nitrogen and it is a crystalline organic compound. The main ability of urea fertilizer is to promote green leaf growth because it helps in the process of photosynthesis. Advantages of urea are:

  • Good nitrogen content
  • Relatively low cost
  • Non-explosive in nature
  • Has wide application
  1. What kind of fertilizers are used for fruit trees?

Fruit trees need organic fertilizer rich in nitrogen content. So, fruit plants or trees are generally supplied with blood meal, soybean meal, composted chicken manure, feather meal, cottonseed meal and other organic nitrogen sources for better yield. Some trace minerals are also required

  1. What are the symptoms of phosphorous deficiency in plants?

When the plants are young, phosphorous deficiency has the same symptoms as nitrogen deficiency. Some uncommon symptoms of the deficiency are:

  • Stunted growth
  • Abnormal dark green colour
  • Yellowing in plants
  • Unthrifty plants
  1. What are the symptoms of potassium deficiency in plants?

The biggest clue about potassium deficiency in plants is that it first appears on the older leaves. Typical symptoms of the deficiency in plants are:

  • Brown scorching
  • Curling of leaf tips
  • Chlorosis in leaf veins
  • Purple spots under the leaf
  • Reduced root, seed and fruit development
  1. What are zinc deficiency symptoms and what fertilizers contain zinc?

The deficiency of zinc in plants is known by reduced plant height, interveinal chlorosis, brown spots on the upper leaves and distorted leaves. Soil that can cause zinc deficiency is high in pH, high in phosphorous, has a low soil temperature, waterlogged conditions, etc. The common zinc fertilizers used for the plants are zinc chelates (14%), zinc sulphate (25-36%) and zinc oxide (70-80%).

  1. How is manure prepared and what elements are present in it?

Farmyard manure is the commonly used manure in agriculture and is basically prepared from cow dung, cow urine, waste straw and other dairy waste materials. The cow dung is obtained from the cowshed; put in a pit and is allowed to decompose for a certain period of time. This compost is used as manure to enrich the soil. Manure or compost contains nitrogen, phosphorous, potassium, calcium, sulphur, zinc, copper, manganese and iron.

  1. What are the advantages of organic manures over conventional chemical fertilizers?

The benefits of using organic manures over chemical fertilizers are:

  • Manure is slower and gentler on plants and does not get washed away by water or heavy rain.
  • Manure improves the soil condition by retaining nutrients and moisture.
  • Causeless or no damage to the plants due to the slow release of nutrients into the soil.
  • Do not pollute the water resources.
  • Chemicals when not used get leached away if fertilizers are added, but manure keeps protecting the soil.
  1. How much manure is needed for the farm?

It is estimated that 100 sq ft of an area needs 20 to 30 pounds of manure, but it should be composted before use, otherwise, it can injure the plants.

  1. What items can be used to prepare compost manure?

Some kitchen items which can be used for creating compost manure along with animal manure are fruit and vegetable scraps, eggshells, coffee grounds, loose leaf tea, stale cereal, seaweed, kelp, peanut shells, leaves trimmed or pinched leaves from the garden, finely chopped wood and bark chips, grass clippings, flowers, dead houseplants and autumn leaves.

  1. What elements should not be used while composting manure?

Some elements or substances that cannot be used for composting are coal ash, coloured paper, diseased plant, aluminium foil, plastics, metals, meat, bones, dairy, pet droppings and synthetic chemicals (herbicides).

  1. What form of fertilizer is good for farms?

For small farms and gardens, granular and liquid forms of fertilizers are used and these can be either water-soluble or slow-release type. Slow-release type fertilizers are considered good for plants because they keep supplying nutrients to the plants for several months. For fast growth and development, liquid fertilizers are considered better.

  1. What are bio-fertilizers and how do they differ from normal fertilizers?

Biofertilizer is a medium that contains live micro-organisms like bacteria and fungi that fix the nitrogen in the soil naturally from the atmosphere. They are extremely eco-friendly whereas conventional fertilizers are created using chemicals.

  1. What are some bio-fertilizers used for farming?

Currently, there are five different types of bio-fertilizers used in agricultural practices such as Rhizobium, azotobacter, azospirillum, phosphate solubilizing bacteria, and mycorrhiza. Among these Rhizobium, azotobacter, azospirillum and blue-green algae are the traditional forms of bio-fertilizers.


In case if you are interested in this: How To Grow Organic Lettuce.



  1. Very Good information.Please give give some more information on use Liquid fertilizers. Can they be mixed with pesticides for spraying..Dr Pullamraju




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