Nitrate (nitrate-N) is commonly found at some level in irrigation water. For corn in Minnesota in a normal irrigation year, when nitrate concentrations in irrigation water are below 10 parts per million (ppm), or 10 milligrams per liter (mg/L), we don’t recommend making adjustments to your fertilization plan. This is because the University of Minnesota’s corn fertilizer guidelines already account for this. If nitrate concentrations are greater than 10 ppm or the amount of irrigation during the season is substantially greater than normal, the nitrogen added through irrigation should be accounted for because: Excess nitrogen in some crops can result in vigorous and excessive vegetative growth, leading to uneven or delayed maturity and reduced quality.
The nitrogen credit from irrigation water means you can save money on nitrogen fertilizer costs, especially in dry years like 2021 (more on this below).
Exceeding a crop’s nitrogen needs can result in nitrogen loss and groundwater contamination.
Moreover, particularly in years like 2021 when we are experiencing excessive heat and very little rain, there is less potential for nitrogen loss from the fertilizer that has been applied and from nitrogen mineralization from the soil. So, it’s important to account for the nitrogen in the irrigation water in the total nitrogen application plan. Also, don’t forget that applying nitrogen past-tasseling will not help improve corn yields.
Source: umn.edu
Photo Credit: istock-laughingmango
Categories: Minnesota, Crops, Corn