FARGO, N.D. — Dig up a corn root ball and you’ll see how the roots extend in all directions. They have been genetically modified to aggressively chase moisture and nutrients in the soil.
At a soil depth of about one foot, the longest roots from one row finally meet the longest roots from the next row. This is true regardless of row spacing, the difference being that the two rows of roots meet sooner with narrow spacing.
If you’ve placed your top-up nitrogen mid-row, that’s where the root tips will find it.
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However, at that distance from the stalk, the root tips aren’t nearly as strong or plentiful as they are right below the stalk.
Compared to the dense centre of the root ball, these distant tips cannot suck up as much nutrients and they cannot contribute as much to the health of the plant or total yield.
The number of root hairs and the degree of root-to-soil contact are always highest at the heart of the root, so that’s where uptake of water and nutrients is highest. Eighty percent of the root mass is located within a seven inch radius of the stalk.
“Late-season N application plays two roles,” says the 360 Y-drop website. “It provides needed nitrate and ammonium for plant nutrition and it stimulates microbes in the soil to mineralize and release late-season ammonium.”
The recommendation from 360 Yield Center is to run the Y-drop down every row, so every root receives an application from both sides.
However, at a price of C$800 per row unit, some growers want to cut their investment by half and run the Y-drop in only every second row. They argue that upping the rate still puts plenty of liquid fertilizer on top of every root.
The company responds that it’s important to deliver nutrients to a location that most consistently stimulates microbial activity throughout the root zone, which is located in a radius beneath the stalk base. They say one side only does not constitute a radius.
The natural funnelling structure of a corn plant is such that even 2.5 millimetres of rain across a field is magnified at the base of the corn plant. Funnelled water helps move nutrients into the root zone if it’s applied on both sides of the plant.
“In contrast, if we apply nutrients to only one side of the stalk base, the likelihood that nutrients move throughout the entire area is lower and you could be missing an opportunity to reach full potential and maximize nutrient efficiency and uptake,” the company says
Placement is critical for optimal nutrient use, but so is the timing of that application. Seventy-five percent of the nitrogen a corn plant uses is consumed after vegetative stage 10.
The best time for that final nitrogen application can be as late as tassling, which provides a wide window of opportunity to top up the nitrogen levels, any time from V6 to VT.
