By Craig Madsen
We have been discussing how nature can capture some of the nitrogen from the atmosphere. Remember that 78% of the air we breathe is nitrogen. Once we have determined through a soil test, a plant tissue, or sap analysis that nitrogen is needed, how do we increase the effectiveness of the applied nitrogen?
Nitrogen is a fundamental part of plant life as it forms an essential part of proteins, phosphatide nucleotides, alkaloids, enzymes, hormones, and vitamins. It is an essential component of chlorophyll, which is required for photosynthesis.
Most applied nitrogen is converted to the highly leachable nitrate anion that can only be stored on positively charged soil organic matter. A significant amount of soil organic matter has been depleted in our soils over recent decades. Nitrogen applied above the immediate requirements of the plant results in loss of carbon (soil organic matter) because the soil biology will balance the carbon-to-nitrogen ratio in the soil by eating the carbon (SOM). Research has shown that up to 40% of applied nitrogen is lost to the environment. Fall application and applying large amounts at seeding result in the highest loss of nitrogen and greatest impact in loss of carbon from soils.
Increasing the efficiency of Nitrogen inputs can be accomplished in several ways:
Apply nitrogen at the time and rates the plant needs it.
Stabilize starter N with humic acid. The inclusion of humate with ammonium N or nitrate N fertilizers creates a non-leachable N supply that is also less prone to volatilization (losses to the atmosphere) because ammonium humates and urea humates cannot leach or volatize. (Citation: “Bioactive carbon improves nitrogen fertilizer efficiency and ecological sustainability” - Peter Espie and Haley Ridgeway https://www.nature.com/articles/s41598-020-60024-3#Sec )
Foliar spraying of urea – A foliar application of urea is up to 6 times more efficient than soil applied. This is probably the single most important N efficiency strategy. Urea is an amine. When urea is applied to the soil, the urease enzyme converts it from the amine form into ammonium nitrogen, then microbes convert it to nitrate nitrogen. The plant absorbs nitrate nitrogen from the soil. The plant must first convert the nitrate nitrogen to the amine form. This process costs the plant a lot of energy. If the plant does not have the energy available, the nitrates cannot be converted to protein and accumulate in the tissue. Higher levels of nitrogen in the leaves can attract insects. Once the amine is formed it is a simple and rapid process for amines to become amino acids, and then protein. https://www.sare.org/publications/manage-insects-on-your-farm/managing-soils-to-minimize-crop-pests/impacts-of-fertilizers-on-insect-pests/
What if you bypassed this process and foliar sprayed urea directly onto the leaf? With this strategy. the amine is simply and rapidly converted to protein with very little energy expenditure. A foliar application to a broadacre crop can be equivalent to a side dress of six times that amount, and there is no leaching, no volatilization and rapid protein formation. It is important to recognize that plant immunity is protein-based. Higher protein is not just higher premiums. It also equates to less pest pressure.
There is one important tip to maximize this strategy: Always combine the foliar urea with humic acid to form a stable urea humate. The humic also buffers any potential burn while also increasing N uptake by 30%. Humic acid is also a plant growth stimulant. https://www.sciencedirect.com/science/article/pii/S2405844020319435
It is important to note that excess nitrogen can cause as many problems as too little nitrogen. Excess nitrogen can result in the loss of organic matter as biology balances the carbon-to-nitrogen ratio. This organic matter loss can increase weed, insect, and disease pressure. It can also negatively impact animal health and result in loss to the environment through leaching.
Craig Madsen has over 30 years of experience focusing on ecosystem management issues. For the last 20 years he has co-owned and operated Healing Hooves, a vegetation management business using goats. He has been a Certified Educator in Holistic Management since 2001. He was a Range Management Specialist with the USDA Natural Resources Conservation Service for 14 years. He graduated from Nicole Masters CREATE Coaching Program in April 2022. The CREATE Program was a deep dive into soil ecology, the interrelationships between plants, soil biology, and ecosystem function. He is currently a CREATE Fellowship Coach https://integritysoils.com/pages/create-fellowship-coaches. Craig is the current president of Roots of Resilience.