Nitrogen Fertilizer: Organic and inorganic sources for Crop Production
Authors: Rajendra Kumar Yadav, Sunita Yadav, Chiranjeev Kumawat And Deep Mohan Mahala
PhD. Scholar, Division of Soil Science and Agricultural chemistry, ICAR-IARI, New Delhi-110012


Introduction:

Nitrogen is generally the most difficult nutrient to manage for crop production. Cover crops and composts can contribute substantial N for crops, but it is challenging to synchronize N release from these materials with the plant demand. Various commercial inorganic and organic N fertilizers are available, but their costs may be prohibitive in many situations. Careful management of organic N sources is required to meet crop requirements, while avoiding undesirable N losses to the environment. most common sources of nitrogen organic and inorganic sources are given below in brief.

A. Organic sources:

1. Animal Manure: The waste from grass eating animals is an excellent source of nitrogen. Make sure the manure is well composted; since raw manure can not only burn your plants, but the nitrogen is more volatile and can leach away. Also, composting at a high temperature for an extended period of time can generate enough heat to kill weed seeds present in the manure.

2. Compost: Organic compost contains all of the nutrients essential for healthy plants, including nitrogen. Although the exact dosage varies depending on what was composted, overall the product is one of the best ways to enrich and improve your soil.

3. Green Manure: Cover crops - such as alfalfa, clover, peas, and other legumes - are able to absorb nitrogen from the air and release it into the soil. Growing these cover crops in your garden improves the soil just by living in it. Tilling cover crops into the ground at the end of the growing season results in a double dose of nutrients and natural compost. If you rotate crops in your vegetable garden, be sure to add green manures to the rotation cycle.

4. Blood Meal: Made from the waste of slaughterhouses, blood meal is a potent source of nitrogen than can burn your plants if over applied, especially on young seedlings. Because it's water-soluble, blood meal can be mixed with water or applied through your irrigation system.

5. Cottonseed Meal: This organic source is slightly acidic and provides nitrogen in a fairly slow-release form.

6. Feather Meal: Chicken feather meal is often dried and formed into pellets which make an easy to use granular fertilizer. Feather meal has a moderate release rate, as soil microbes break down the proteins to make the nitrogen available to plant roots.

7. Soybean Meal: Similar to cottonseed meal, soybean meal is a slow release source of nitrogen made from ground soybeans.

B. Inorganic sources

1. Urea: Urea is a highly soluble, dry material. Urea can be used as a starter, broadcast or top dress application and can be used in fertilizer mixes (dry or liquid). Advantages of \urea are its high N content (45 to 46%), relatively low cost per lb of N, and rapid conversion to plant-available N. If urea is surface applied and not incorporated (either by rain or tillage), N losses to the air (as ammonia) can approach 40% of the applied N. urea application by broadcast or basal dose.

2. Urea Ammonium Nitrate: Urea ammonium nitrate (UAN) is a soluble, readily available N source with 28-32% N prepared by mixing of ammonium nitrate and urea. UAN can be broadcast or placed in the starter band. If broadcast, UAN should be incorporated into the soil as the urea portion is subject to volatilization. However, because of its lower % of N in urea and ammonium form, volatilization losses per pound of N from UAN will be lower than for urea.

3. Ammonium Sulfate: Ammonium sulfate is a soluble, readily available source of N and sulfur (S). Dry forms contain 21% N and 24% S, Ammonium sulfate is well-suited as a top dress application as it has a lower N volatilization risk than surface-applied urea. Also, where S is needed, ammonium sulfate is a good source of S.

4. Anhydrous Ammonia: Anhydrous ammonia has the highest percentage of N of all fertilizers (82% N) and tends to be the cheapest N source. It is a high-pressure liquid that can be deep-banded before, at or after seeding provided that there is no direct seed contact. It must be stored under high pressure, which requires specially designed, well-maintained equipment and facilities should be well-protected for safety reasons.

5. Ammonium Nitrate: Ammonium nitrate is an odorless salt with 33 to 34% N. It can be surface-applied or incorporated into the soil. It contains both ammonium and nitrate resulting in reduced volatilization risk as compared to urea, and the nitrate provides a directly available N source. Since it contains ammonium, this fertilizer also lowers the pH of the soil.

6. Potassium Nitrate: Potassium nitrate, also known as saltpeter or nitric acid, is considered a specialty fertilizer. It is a colorless transparent crystal or white powder with 14% N and 46% potassium (K). Potassium nitrate does not lower the soil pH.

7. Mono-Ammonium Phosphate: Mono-ammonium phosphate (MAP) contains readily available sources of N (11%), P (52%) and S (1.5%). MAP is a dry granular material that is applied alone or often blended with other materials such as potash. It can be broadcast, band-applied or placed in the seed furrow. MAP can lower the soil pH but is an excellent starter fertilizer.

8. Di-Ammonium Phosphate: Di-ammonium phosphate (DAP) is dry fertilizer that contains readily available sources of N (18%) and P (46%). Formation of free ammonia produced after mixing of DAP with soil can cause seedling injury. To prevent such injury using DAP, it is recommended to limit band applications.

9. Chilean Nitrate: Chilean nitrate can be used in conventional and organic cropping systems (permitted for use by USDA/NOP in 2003). It contains 16% of a readily plant-available form of nitrate-N and sodium. It is available in a dry, flow able prill form.


About Author / Additional Info:
Ph.D Scholar, Division of Soil Science and Agricultural Chemistry, IARI New Delhi ,India