Variable Rate Nitrogen Application in Corn Production Jimmy Stotts Precision Ag 4213

Introduction Effective Management of fertilizer nitrogen (N) in corn production is needed to maximize economic return for producers and control N losses that can cause environmental problems. These environmental concerns with N use in corn are mainly focused on nitrate leaching to groundwater and surface water nitrate contributions to Gulf of Mexico Hypoxia.

Reasons for Variable Rate Applications More economic return Less environmental risk Less fertilizer applied Different soil types No Grid Soil Sampling

Environmental cures Less amount of nitrogen leaching Not near as much environmental risk with these variable rate applicators

Application Systems GreenSeeker Great for late applications of fertilizer These are Greenseeker sensors located on a Hagle High-Clearance Sprayer

Application Systems RT 500 Greenseeker Sensors on an Apache Spraying machine 2ftx2ft Resolution Good for early fertilization

Other Application Systems Soil doctor Standard Ag Coulters Paired “Rolling Electrodes” “Plug Into The Soil” One is positive and the other is negative Conductivity Electrochemistry Complex resistivity

Challenges For VRT in Corn The Potential Cost Savings Can be minimal When all costs of developing and executing the variable rate strategy are considered the net return may be insufficient to cover the added expense.

Challenges For VRT in Corn Prescriptive Nitrogen Strategies Involve Risk These could include unusually favorable growing conditions or yield limiting events such as frost, hail, stalk lodging, pests, drought, or N losses due to excessive rainfall and denitrification

Check Strips (NRICH) Needs to be several uniform check strips throughout the fields A uniform rate should be applied based on current local or university recommendations Additional strips with 50lb/ac above and below the recommendation rate may be helpful also Can be harvested as separate loads on yield monitors or as a side by side comparison with a weigh wagon

Nitrogen Cycle

Application If rates of applied N can be matched to actual corn N requirements throughout production fields, the economic and environmental goals of N management could potentially be achieved to a greater extent than would be possible with a single N rate applied to the entire field

Growth Chart

Application time (V5) Tassel formation (V6) Yield can be closely predicted (V9) Ear shoots develop (V12) By waiting until (V12) it would be better for predicting potential grain yield

Adoption Of Technology Variable Rate methods involving assessment of plant N status Through remote sensing during the growing season may have potential if the cost of these technologies does not exceed the value of the benefits provided

RETURN Doerge(2001) estimated that the Nitrogen cost savings is in the range of 5-15$/ac That is big time on 1000 acre farm

Sources http://www.neuse.ncsu.edu/nitrogen/ http://www.dasnr.okstate.edu/Nitrogen_use http://www.ppi-far.org/far/farguide.nsf http://www.ppi-far.org/ppiweb/ppibase.nsf/ http://www.soils.wisc.edu/extension/ http://www.soildoctor.com/nmgmt.html http://geospatial.osu.edu/conference/ http://msucares.com/pubs/bulletins/b1129.pdf http://www.riecks.com/2577-31.html