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
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
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
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