Minnesota Crop News

By: Dan Kaiser, Extension nutrient management specialist Earlier this year, I wrote about recent research showing that alfalfa benefits from sulfur fertilizer application. Those studies seem to confirm the current U of M alfalfa fertilizer guidelines for sulfur application, which suggest applying 10 to 25 pounds of sulfur fertilizer per acre, depending on overall production and soil organic matter concentration in the top six inches of soil. But what source of sulfur fertilizer is best for alfalfa? That’s the current focus of two studies funded by Minnesota’s fertilizer check-off dollars through the Agricultural Fertilizer Research and Education Council (AFREC) . Sulfur fertilizer sources In these two new studies, we compare specific classes of sulfur fertilizer sources at three different rates. One area of interest is whether different elemental sulfur sources can oxidize enough sulfur in a given year. There are two main options for growers if they wish to apply elemental sulfur. The

By: Dan Kaiser, Extension nutrient management specialist While much of the field work around Minnesota has slowed, the rising cost of fertilizer and uncertainty surrounding fertilizer availability for spring 2022 may have some still thinking about late fall application options. Urea can be a tempting option for fall application because it is easy to apply with a floater, but is this a good practice? Urea is a dry source of nitrogen that can be lost to the atmosphere via ammonia volatilization and to water via nitrate leaching. Risk of volatilization is more immediate and can occur regardless of soil temperature. If urea is applied on the soil surface, or even with shallow incorporation, it is at risk of loss via volatilization as it dissolves. Many people think that as long as it is 50 degrees or colder, urea cannot be lost to water. While products containing NBPT, such as Agrotain, can help delay this process, there still can be risk of loss if urea is not incorporated into the soil m