As the 2010 growing season heats up and farmers across the state get ready to implement fertilizer management programs, the Minnesota Department of Agriculture (MDA) is reminding them of a potential wild card ‑ the nitrogen content of their irrigation water. 

According to MDA Water Quality Advisor Jennifer Gallus, accurate nitrogen crediting requires knowledge of the nitrate concentration in the irrigation water, and an estimate of the amount of water normally pumped during the period when the crop in question is actively taking up nitrogen.  To assist irrigators in properly determining nitrogen content, MDA is partnering with the East Central Irrigators Association to provide free nitrate testing during the 2010 irrigation season. 

“Proper nitrogen crediting and nutrient management leads to improved water quality,” Gallus said.  “Some farmers may already be taking the proper nitrogen credits for soybeans, alfalfa, and manure, but in some cases they may not be aware that their irrigation water also could be a significant source of nitrogen.”

Corn aggressively uses nitrogen from the time it is waist height to silking stage.  After silking, nitrogen uptake is essentially complete and no additional credits should be included. For potatoes, the uptake period starts about 20 days after emergence and continues for approximately 40 days.

To sample the irrigation well, allow the pump to run for 20-30 minutes prior to sampling.  Collect about ½ cup of water in a Ziploc bag or a clean jar.  Prior to filling the container, label it with a waterproof marker.  Identify with a unique number that you will remember. Drop off the sample(s) at a location listed below anytime during normal business hours from June 1 to June 15, 2010.  Call the drop site after June 21 to find out your results. 

Drop sites include:

  • Helena Chemical in Royalton;
  • Benton Soil and Water Conservation District in Foley;
  • Centra Sota in Santiago;
  • Crop Production Services in Big Lake; and
  • Federated Co-op in Isanti.

Postcards will be sent in late May to East Central Irrigation Association member irrigators as a reminder about this opportunity.  Non-members are also encouraged to participate free of charge. Names and locations of wells will not be collected.  For more information, farmers are encouraged to call Gallus at (320) 543-3150.

Source: Minnesota Department of Agriculture