Corn N Timing: Full Yield Can Be Achieved Even With Late Applications

DR. ANTHONY OHMES

JACKSON, MO.
   In very general terms, corn requires nitrogen (N) for growth, phosphorus (P) for root development and potassium (K) for strength and kernel quality. It also needs calcium (Ca), magnesium (Mg), sulfur (S), and Micro’s such as zinc (Zn). Deficiency from the secondary nutrients may be observed on sandy, low organic matter and low cation exchange capacity (CEC) fields. Uptake of nutrients is reduced when pH falls below 5.8. When in doubt a soil test will help determine levels. Corn begins rapid growth at V6 (6 leaf) and utilizes 65 percent of N from V6 through VT (tasseling) , it uses an additional 20 percent for grain formation.
   Research by Peter Scharf has shown that late season applications of N through silking has increased yield potential, especially when plants were showing signs of N stress. Visual assessment above crop canopy along with tissue tests mid- to late-season could help determine a need for additional N to help the crop reach full yield potential. If concerned, collect leaf samples for analysis from upper leaves on plants over 12 inches. Collect ear-leaf tissue on tasseling plants in order to get an accurate assessment of plant needs.
   More information is available on the Missouri nutrient management website, http://nmplanner.missouri.edu/, including best management practices, timing, rate and loss of nitrogen. There is a nitrogen monitoring site that helps identify danger areas for nitrogen loss titled “Nitrogen Watch 2016” found at
http://plantsci.missouri.edu/nutrientmanagement/Nitrogen/Nitrogen_watch_2016/nitrogen_watch_2016.htm. ∆
   DR. ANTHONY OHMES: Agronomy Specialist, University of Missouri Extension