Tim Smith from Cropsmith and Fred Below, Ph.D., from the University of Illinois, discuss their research on applying nitrogen on soybeans, when it makes sense to use it, the optimal timing and application rates and what role soil plays in providing additional nitrogen.
Nodules on the soybean root system
Nodules enclose nitrogen-fixing bacteria
Active nodules are pink inside
Both parties benefit; the bacteria in the nodules receive sugar from the plant and the nodules give the plant nitrogen
Temperature, soil acidity, water availability and soil aeration can all have a huge impact on nodule activity and nitrogen fixation
How much of the soybean’s nitrogen comes from the nodules?
The rest comes from the soil
Soybeans are a huge nitrogen-requiring crop
How much nitrogen do soybean plants need to accumulate per each bushel of grain?
4 – 5 pounds of nitrogen per bushel
Facts about soybeans and nitrogen
There is no such thing as a soybean nitrogen credit
Soybeans remove about a pound of nitrogen from the soil for each bushel produced
Can supplemental fertilizer nitrogen increase soybean yield?
Yes, no negative impact on nodule development and applying 100 lbs. of nitrogen preplant or V3 tended to increase nodule activity
Was there a best time to apply nitrogen fertilizer to soybeans?
Yes, although yield increases were observed for all application times, preplant applications regularly increased yield over 3 years
Do fertilizer nitrogen applications inhibit nodule formation and activity?
No, fertilizer nitrogen applications only had minor effects on nodule number and color
The Illinois Soybean Association (ISA) checkoff and membership programs represent more than 43,000 soybean farmers in Illinois. The checkoff funds market development and utilization efforts while the membership program supports the government relations interests of Illinois soybean farmers at the local, state, and national level, through the Illinois Soybean Growers (ISG). ISA upholds the interests of Illinois soybean producers through promotion, advocacy, and education with the vision of becoming a market leader in sustainable soybean production and profitability.