Broccoli is Big on N Uptake

By Patrick Cavanaugh, Editor

Utilizing funding from the Fertilizer Research and Education Program (FREP), Richard Smith, UC Farm Advisor Monterey County, looked at the nitrogen uptake by cool season vegetables, in particular, cole crops.

With the funding Smith did work on the nitrogen uptake by broccoli, cauliflower and cabbage. Smith noted that he is about half way through the survey and preliminary numbers show in particular the amount of nitrogen picked up by broccoli is quite high—on average 300 pounds of N per acre.

Smith noted that even though the nitrogen uptake by broccoli is noted in the literature, it still surprised him that it was routinely as high as 300 pounds per acre.

“We are surveying fields that are growing very well in order to get real world

Information. Remarkably, growers are not even applying anywhere near that amount of nitrogen,” said Smith. “They are actually putting on about 180 pounds on N. So the bottom line is that broccoli is actually savaging nitrogen from the soil. It’s taking up more than is applied. The big question is: Where is broccoli getting all this nitrogen,” asked Smith

“We have been growing broccoli for 80 or 90 years in the Salinas Valley and here is something that we did not realize that it was capable of doing. And it may be due to it’s rooting structure, or density, but its illustrating that it is a tool to capture nitrogen that would otherwise be susceptible to loss,” Smith said. “We could use broccoli as a rotation crop. 

In addition to fighting Sclerotinia, it may be doing something else too, in terms of managing nitrogen, by capturing N and bringing it back up to the surface.  This is all good news because we now know we have a system of a rotational crop that can capture N deep in the soil profile,” he noted.