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Ontario Grain Farmer Magazine

Evaluating strip tillage and fertility placement to reduce soil and P loss

Principal Investigator: Ben Rosser

Research Institution: Ontario Ministry of Agriculture and Rural Affairs (OMAFRA)

Timeline: April 2018 – December 2021

Objectives:

  • Evaluate competitiveness of fall phosphorus (P) and potassium (potash, K) fertilizer placed through strip tiller vs. broadcast and incorporated.
  • Evaluate competitiveness of P and K fertilizer placed with fall strip tillage pass vs. fertilizer placed with spring tillage pass.
  • Evaluate importance of planter banded fertilizer in a fall strip tillage fertility system.
  • Evaluate yield performance of strip tillage versus conventional tillage.

Impacts:

  • The development of an economically competitive conservation system using strip tillage may lead to reduced losses of phosphorus (P) fertilizer from the field.

Scientific Summary:

Run-off from agricultural land has been identified as a contributor of phosphorous (P) loading to Lake Erie and has received considerable public attention for this role. Soil conservation efforts such as no-till have delivered reductions in particulate P loading. However, these efforts have been offset by an increase in dissolved P, which have been partly attributed to the broadcasting of fertilizer on soil surfaces which do not receive incorporation and are susceptible to loss to surface water. Future conservation strategies for long term sustainability will need to address both issues – reduction in erosion (reduces particulate P loss) with simultaneous incorporation of fertilizer into the soil (reduces dissolved P loss). Strip tillage is one system which could potentially address both reduced tillage and sub-surface placement of larger amounts of fertilizer. Strip tillage has been investigated and promoted as a conservation tillage system for nearly 20 years in Ontario and is now seeing considerable momentum and uptake in the farm community. More research is required to evaluate the ability of strip tillage to replace surface applications of P and potassium (potash, K) fertilizer, and further refine management recommendations for current corn hybrids and strip tillage technology for those who are converting to it.

This project built on previous research investigating response of P and K fertility and placement in strip tillage systems relative to broadcast and conventional tillage systems, but focused on a different geography (Perth, Wellington, Brant and Oxford counties). Trials investigated the ability of strip till and fertility placement to compete competitively with broadcast fertilizer and conventional tillage systems through evaluating:

  1. Fall PK fertilizer placed through strip tiller vs. broadcast and incorporated.
  2. PK fertilizer placed with fall strip till vs. placed with spring strip till.
  3. Importance of planter banded fertilizer in a fall strip till fertilizer system.
  4. Yield performance of strip tillage versus conventional tillage.

Trials were conducted with co-operators under conventional tillage and for fertilizer response evaluation, which favoured locations with low P or K fertility. Treatments investigated a variety of tillage and fertilizer placement methods to answer the above objectives over three growing seasons. A total of 15 trials have been completed over 3 growing seasons (2019-2021) following soybean or cereals.

Results

Trials were conducted at 15 locations from 2019 to 2021 (Bornholm, Drumbo (2019 and 2020), Elora (cereal residue), Elora (soybean residue), Kintore (2021), Shelburne (2020 and 2021) and Winchester (2019)). Trials ranged from loam to clay loam soils with either cereals or soybeans as previous crops. To investigate yield responses to fertility management, field testing for low P & K were favoured.

Strip tilling was completed with a 6” x 30” Kuhn Krause Gladiator shank-style strip tiller operating 6” deep, while full width tillage was completed with 2 spring passes of a finishing disk/harrow or cultivator leaving mostly bare soil. Full width tillage was fall chisel plowed or disked at some locations. Strip till fertilizer was applied by banding tube behind the strip tiller shank at 4” depth (balancing crop safety with starter response) while planter starter fertilizer was applied by 2” x 2” band. Broadcast treatments were surface broadcast between spring tillage passes. To investigate yield response to P & K placement and timing, 60 Ib-P2O5/ac and 60 Ib-K2O/ac (mono-ammonium phosphate and muriate of potash) were applied for all treatments (roughly 1 corn crop removal equivalent, high enough to elicit yield responses, not too high to saturate responses or cause significant crop safety issues). All treatments received 30 Ib-N/ac as urea applied in a 2” x 2” band on the planter, with the balance of N usually applied as UAN sidedress.

Treatments used to investigate strip till P&K fertilizer timing and placement questions included:

  1. Full width tillage, no P or K fertilizer (fertility response control).
  2. Full width tillage, spring broadcast P&K.
  3. Full width tillage, 50% spring broadcast P&K, 50% spring planter banded P&K.
  4. Fall strip till, shank placed P&K.
  5. Fall strip till, 50% shank placed P&K, 50% spring planter banded P&K.
  6. Spring strip till, shank placed P&K.

Based on three years of results (2019-2021) of applying moderate amounts of P&K fertilizer (60 Ib/ac of both P2O5 and K2O) at 15 trials, mostly on low soil fertility:

  1. Yields of spring strip till and P&K were significantly (p<0.05) higher than where P&K was broadcast and incorporated with full width tillage, 4.1 bu/ac greater on average, and significantly higher within 5 of 15 trials.
  2. Yields of spring strip till and P&K were significantly (p<0.05) higher than fall strip till and P&K, 4.7 bu/ac greater on average. Results were variable, with three trials having a large significant response.
  3. Moving a portion of P&K from fall strip till applications to starter fertilizer on the planter the following spring results in a significantly (p<0.10) higher yield (+3.2 bu/ac) compared to where all P&K was only applied through fall strip. Significant responses were observed within one location.
  4. When comparing similar nutrient placements, yield performance of strip till and full width tillage were similar. Spring strip till and P&K was similar yielding to other treatments which included starter fertilizer, but significantly higher yielding than treatments which did not. Fertilizer availability (placement, timing) within tillage system appears to be a strong driver of yield responses.

In past research, it has been noted that no-till has reduced particulate phosphorous losses but increased soluble/dissolved phosphorous losses relative to conventional tillage, not necessarily offsetting P risks associated with conventional tillage. Preliminary results from one rainfall simulator runoff trial have shown:

  1. Strip till to reduce soluble reactive phosphorous (SRP) and total dissolved phosphorous (TDP) losses relative to no-till, but still be higher than conventional tillage.
  2. That where 60 Ib-P2O5/ac fertilizer was applied, slightly higher SRP levels were observed (but not TDP), but these differences were much less than observed across tillage treatments.
  3. Particulate phosphorous (PP) losses were significantly higher than soluble/dissolved losses, but in contrast to expectations, losses increased as tillage was reduced. There are a couple of thoughts as to why this was observed:
    1. Losses appeared to be strongly driven by runoff amounts, as both PP concentration, and PP loss amounts increased with runoff volumes (naturally, as concentrations are multiplied by runoff volumes).
    1. Runoff volumes increased as tillage was reduced (0.54 L for conventional tillage, 2.83 L for strip-till, 7.88 L for no-till).
    1. Rainfall shelters were placed after tillage/fertilizer treatments were conducted to prevent tilled soil or nutrient loss from natural rainfall events, thus soil beneath shelters was relatively dry. Controlled pre-wetting was required to generate sufficient runoff for collection during the simulation.
    1. Even at pre-wetted soil moistures (wetted to the point of not generating runoff at the time of application), tilled soil (tilled strip in strip till, conventional tillage) was acting more like a sponge, absorbing rainfall simulator water, than untilled soil (no-till, untilled strips in strip-till) where it eventually started to run off.
    1. While pre-wetting helped produce runoff, it was still not able to generate the runoff of plots which never received rainfall shelters (no-till, no fertilizer (unsheltered) runoff volume = 13.67 L, no-till, fertilizer (sheltered) runoff volume = 2.09 L).
    1. A greater amount of pre-soaking over a longer period of time, or leaving plots uncovered for all but very excessive forecast rainfalls may better reflect losses from saturated soils, such as during the non-growing season. It is possible tilled soil losses could be much different under these conditions.
    1. It is possible these results do reflect runoff and P loss realities on relatively drier soils (e.g., growing season) for these treatments.
    1. Fertilizer treatments did not appear to be a strong driver for Particulate Phosphorous (PP) or Total Phosphorous (TP) losses in strip till and no-till. The unfertilized treatments averaged much higher than the fertilized treatments (but there was significant variability across reps – this is expected to be due to general background variation more than a treatment effect).

This research has demonstrated the competitiveness of strip till and fertility systems relative to conventional tillage and provides values for various fertilizer placement and timing strategies for growers to consider when building strip tillage systems on their farms (e.g., trade off logistics, costs of various placement and timing strategies versus the yield benefits these strategies may provide).

There are still a lot of questions on the strip till fertility front, particularly how to safely apply larger amounts of fertilizer where crop injury could be a concern (reduce the need to fertilize ahead of other crops in rotation, such as can be done with broadcast and incorporate applications in conventional tillage), what rates of fertilizer are safe to apply for the various placement options with strip till (various shank depths, or mixing with coulters), how to place fertilizer in the strip for maximum starter fertilizer effect (e.g., some shallow banding placement of P and K fertilizer) potentially mimicking or limiting the need for starter fertilizer on the corn planter, how to balance placement of large amounts of fertilizer with starter effects (e.g., double banding deep and shallow fertilizer to balance safety and starter placements, or blends), and management strategies for applying greater amounts of nitrogen in spring for those who would like to come back for late in-crop N applications (e.g., chest high corn stage).

Many of the above are common questions from growers and finding solutions to these problems would continue to remove some of the logistical challenges of strip till (which may be limiting adoption) or help producers to get the most out of existing systems. It is expected this could continue to drive adoption of an efficient and competitive-yielding conservation tillage system.

External Funding Partners:

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

Project Related Publications:

None.