As we continue to learn and study nitrogen I began measuring nitrate levels in a field on my home farm in Michigan. The field was planted on May 9th and received 15 lbs of actual N via AMS broadcast and incorporated on May 2nd. An additional weed-n-feed broadcast application of 60# of actual N via 28% occurred on May 13th. The corn field is at the V8 stage so approximately 12% of total N uptake has occurred. Conditions have been below normal at approximately 3 inches less than normal rainfall since planting. We have received close to 3 inches of rain in the last month.
May 2nd: 15# N AMS broadcast incorporated
May 13th: 60# N UAN weed and fee broadcast
I pulled two sets of samples, one set directly in the row (0″ from plant) and a second set in the middle of the row (15″ from plant). The results tell an interesting story. Even though the field was broadcast with even distribution of product across the whole field, we see that the nitrate levels are much lower in the row than the middle of the row and that over time the nitrate levels in the middle of the row are not dropping as quickly. We already see a 8 ppm difference in terms of placement resulting in close to a 30# N difference.
It’s important for us to understand where our root system is. The biomass we see above ground, is the exact mass we expect underground. We see concentrations of our root mass up to 7″ away from the stalk. Yes, we do expect canopy closure at V8, but still the majority of our roots are within that root ball. Nitrogen is mobile with water which moves through our soil vertically, so placement right over that root ball (7″ from stalk) is the most efficient placement of nitrogen.
Looking at the data two things jump out:
- When we think of uptake, it’s simple – where the roots can be found is where the N uptake will be at its highest.
- As conditions have turned dry, the movement of the nitrates laterally from the middle of the row have slowed.
Placement of N is vital for optimum NUE and 360 Y-DROP allows us to squeeze out as much potential we can out of each unit of N. Although we understand the benefits of 360 Y-DROP in a wet year the advantages of placement of N in a dry year may be just as important.
