What is it ? How does the plant use it ? How to calculate N units ? What are the management plans to use it ?
How can we figure out our crop's need for N ?
All of those questions and many more are just a stroke on this amazing subject.
It can be found in the Atmosphere as N2 (Nitrogen), N2O (Nitrous Oxide), and many other gaseous forms.
Will be available for plants after it's been fixed to the soil solution from the air by bacteria or industrially.
The most common form of N in the soil is in the Organic Matter (OM) and is known as the Organic Nitrogen (ON).
ON has a chemical composition that makes it really resistant to any change on its structure which makes it unavailable for plant uptake. Altough it can be converted into Mineral Ammonium (Mineralization) by soil microbes. Subsequent to this it can be converted to Nitrate (Nitrification) by microbial activity. NO3- is the predominant form for plants to uptake it, but also the most mobile and most likely leachable form.
Some of the processes that N is subjected to in the soil are described below
- Immobilization; Happens when there's a high C/N relation situation (high Carbon / low Nitrogen) in the corn stover or wheat chaff or any other crop leftover (usually grains). The available N in the soil will be used by bacteria in order to break down the fibers. It'll get tied up. It causes what's known as N Starvation. It is most likely to happen in no-till to reduced-till systems when the N is spread over the surface (that widens the N availability for the crop because its downward movement will depend on either irrigation or rainfall) and also because the stover accumulates on the surface over time. It is a temporary situation though so it doesn't affect the N rate in no-till or other tillage system. This explains why is is recommended to spread Urea (50 lbs/ac) right before incorporation of the residues after harvest.
- Denitrification: Bacteria in saturated soils (with poor drainage due to compaction, or excessive rainfall, or field depressions where the water tends to stand) use the Oxygen from the Nitrate to breath causing the Nitrate to become into gaseous N (Unavailable for plant uptake and easily loseable).
- Leaching: Excessive rainfall periods and poorly managed irrigation in soils with good drainage can cause this to happen. The NO3- does not bind with the soil particles (clays and OM have negative charges) and gets washed away from the root zone by the water as it infiltrates through the soil profile downward.
- Volatilization: Any form of N that converts into gaseous ammonia (NH3+) like Urea will be subjected to this process. Spinning spreaders are timely effective when it comes to put N on the ground, but no incorporation of it will drastically increase the volatilization.
Liquid N form 30% and 32% at $320/ton and $342/ton, how much is an N Unit ?
1 ton are 2,000 lbs. 30% of 2,000 lbs are pure N so 30% are 600 lbs. So US$320/600 lbs = US$0,53/lbs
32% of 2,000 lbs so 32% are 640 lbs. US$342/640lbs = US$0,53/lb.
That's how the N Units are calculated, why do we need to know that value ?
To make a N recommendation, which will be the most economical amount of nutrient to apply that returns its cost in a yield increase.
Have a good week guys !
