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Ontario Grain Farmer Magazine

Safe fertilizer rate guidance for various fertilizer strategies for strip till corn

Principal Investigator: John Lauzon

Research Institution: University of Guelph

Timeline: April 2021 – September 2022   

Objectives:

  • Determine safe rates of fall applied phosphorus (P) & potassium (K) fertilizer blends (i.e., 6-28-28) through three different fertilizer placement strategies (shallow (4”) shank banding, deeper (6”) shank banding, mixing fertilizer throughout strip with coulter-type strip tiller). This simulates a typical fall strip fertility strategy and would determine when/if fall applied P&K would start to impact crop safety the following spring.
  • Determine safe rates of spring applied P&K fertilizer blends (i.e., 6-28-28) through three different fertilizer placement strategies (shallow (4”) shank banding, deeper (6”) shank banding, mixing fertilizer throughout strip with coulter-type strip tiller). This simulates a spring strip fertility strategy where a grower would like to push both P&K rates in the spring (versus P alone for crop safety) and determine when spring applied P&K would start to impact crop safety.
  • Determine safe rates of spring applied nitrogen (N)&P&K fertilizer blends (i.e., 19-19-19) through three different fertilizer placement strategies (shallow (4”) shank banding, deeper (6”) shank banding, mixing fertilizer throughout strip with coulter-type strip tiller). This simulates a spring strip fertility strategy where a grower would like to push N&P&K rates in the spring (versus P alone for crop safety, such as where higher K rates are desired, as well as higher N rates to allow time for later in-crop N applications), and determine when spring applied N&P&K would start to impact crop safety.
  • Determine safe rates of spring applied N fertilizer (46-0-0) through three different fertilizer placement strategies (shallow (4”) shank banding, deeper (6”) shank banding, mixing fertilizer throughout strip with coulter-type strip tiller). This simulates conditions where a grower would like to push N rates in strip to allow time for making remainder of N application as a late in-crop application, and where spring P&K fertility are of less concern (high soil tests) or met with alternative methods (manure or organic amendments, broadcast applications (K), fall strip applications).

Impacts:

  • Maximize the benefits of the strip till systems by providing guidance for what rates of PK, NPK or N fertilizers can safely be applied with either fall or spring strip till for various placement strategies without causing crop injury.
  • Safe fertilizer rate guidance would provide confidence or starting points for growers who would like to:
    • maximize application efficiency (apply as much product as they feel safe).
    • maximize fertilizer efficiency (apply as much product as they feel safe in the seed zone).
    • incorporate fertilizer into the soil in a reduced tillage system (limiting losses versus surface placement).
    • reduce alternative application strategies (other fertilizer applications made over concerns of being able to safely incorporate fertilizer in strip till).
    • limit the potential for yield loss due to crop injury.
    • reduce trial and error developing strip fertility strategies on farm.

Scientific Summary:

Strip till is increasingly popular for corn production to reduce tillage costs and soil losses while improving fertilizer/tillage logistics. While the portion of Ontario corn acres strip tilled is low, interest and adoption are growing. Safe fertilizer rates are one of the most common strip fertility questions from farmers and agronomists. Tillage prior to corn traditionally incorporates larger amounts of fertilizer to build or replace fertilizer from the crop rotation. Strip till can efficiently incorporate large amounts of subsurface fertilizer, important for crop response and limiting losses, but large amounts of fertilizer in the seed zone creates safety concerns. Safe rates exist for 2” x 2” planter banding, but no research has established safe strip till fertilizer rates in Ontario. Guidance also appears limited in other jurisdictions. Growers are currently using trial and error. Safe fertilizer rate guidance would improve fertilizer efficiencies (product delivery, crop responses) and limit crop injury risks, allowing existing and new adopters to more confidently maximize the benefits of corn strip till systems. 

Unlike 2” x 2” planter banding, developing safe strip till fertilizer guidance presents a challenge as there are a variety of strip fertilizer placements and timings which all carry different risks. Three common placement strategies include i) shallow shank banding (4”) for starter fertilizer effect, ii) deeper shank banding (6”) for safety and iii) mixing fertilizer throughout strip with coulter-type strip tillers. Application timing also varies – some strip till/fertilize in the fall, while others in the spring.

This proposal will evaluate crop safety through applying:

  1. A range of fertilizer rates for three common strip fertilizer strategies:
    1. PK balanced blend (6-28-28)
    1. NPK balanced blend (19-19-19)
    1. N only (46-0-0)
  2. Through three application methods:
    1. 4” shank band
    1. 6” shank band
    1. coulter mixed
  3. For two timings (PK balanced blend only):
    1. spring
    1. fall
  4. Across different soil texture (sandy loam, loam, clay loam).

External Funding Partners:

This project was funded in part by the Canadian Agricultural Partnership (CAP), a five-year investment by Canada’s federal, provincial and territorial governments.

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