Broadcasting urea reduces gaseous losses because it is absorbed by the soil
Farmers who band urea must make sure they do it deep, says an agronomist and fertilizer specialist who has studied the consequences of shallow banding urea.
Otherwise, they are better off broadcasting it.
Farms are becoming larger and fewer operators need to cover more acres, and “all of the sudden, intentionally or unintentionally, we’re cheating on that depth,” Rigas Karamanos told Agri-Trend’s Farm Forum Event in Saskatoon.
“So in other words, what we are doing is shallow banding.”
Producers who band in urea create a microclimate around the granule within the band, which increases the pH in the area up to nine or 9.5, Karamanos said.
This creates an environment where the gaseous losses of urea as ammonia can be high.
Broadcasting urea avoids creating “very hot bands,” Karamanos said.
Nitrogen losses occur when urea is broadcasted, but Karamanos’s work shows that broadcasting urea causes less nitrogen loss than does shallow banding.
The optimal depth in which to band in urea is at least two inches and preferably three inches, said the Koch agronomist.
There are still gaseous losses of urea as ammonia being generated within these deeper bands, but the soil above the band absorbs the ammonia, which minimizes losses.
Gaseous losses of urea are caused by volatilization, which is a physical chemical reaction that starts at around 4 C with urea.
Plants such as canola and wheat do not use a significant amount of nitrogen for the first 10 to 12 days after planting.
“That’s why deep banding found its place. There are no losses during those first 10 days, because whatever gas is created is absorbed by the soil as the gas is moving up towards the surface. That’s the magic of deep banding,” Karamanos said.
He also studied enhanced efficiency products such as such as Agrotain and Super U, which were developed to minimize the losses that occur before the plants can use the applied nitrogen.
“If there are not losses, you don’t need these products,” Karamanos said.
“But when there are losses, those products can indeed help minimize the losses and preserve yields.”
Enhanced efficiency products have generated increasing interest in recent years because of the fluctuation of input costs, a need to show that the industry is being environmentally responsible and a shift from operational efficiencies versus agronomic efficiencies as farms become bigger.
Having a good packing system behind the applicator may reduce nitrogen losses, but Karamanos said it’s not a generic issue.
Losses depend on many variables, such as soil type, moisture and temperature.
Karamanos said producers who apply anhydrous ammonia should expect the same nitrogen losses if they shallow band compared to when they apply nitrogen deeper.