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Ontario Grain Farmer Magazine

Tillage, fertility, and potential phosphorus movement

Principal Investigator: Aaron Breimer  

Research Institution: Veritas Farm Management

Timeline: September 2016 – October 2017  

Objective:

  • To evaluate possible methods to reduce phosphorus (P) movement and how that can be impacted by tillage.

Impacts:

  • Producers in Ontario agriculture will benefit by maintaining or increasing yields, productivity, and profitability while reducing soil erosion, off-target P movement, and increasing soil resiliency.
  • All Ontarians will benefit with reduced P movement into the Great Lakes system and the ecosystem of the Great Lakes will be significantly improved.
  • A reduction in the P levels of the Great Lakes will be of benefit to the public perception of agriculture in Ontario.

Scientific Summary:

This project evaluated strategies to mitigate off target movement of agricultural phosphorus (P), reduce soil erosion potential, yet allow growers to maintain and increase yields. These key elements needed to be investigated concurrently to develop best management strategies that can be implemented by Ontario growers.

Algal blooms in Lake Erie have increased dramatically, and agricultural P has been implicated as a potential contributor. Management techniques need to be developed that will reduce any possible environmental impacts that are related to fertilizer usage, especially regarding P. These systems need to include productivity as well as environmental impact, as both are key elements in sustainability.

Tillage, specifically zone or strip-tillage, and fertility management were evaluated regarding phosphate movement and crop productivity. Phosphorus losses from runoff are less when P fertilizers are incorporated into the soil. Zone tillage creates a tilled zone where fertilizer (P) can be incorporated into the soil, while breaking soil macropores to reduce movement to tiles. Combined, this should reduce the potential for off target movement of P.

From a theoretical crop productivity measure, the zone should allow yields to be achieved similar to conventional tillage, while providing much of the soil erosion benefits of no-till, as only 8” out of 30” is tilled (27%). Ten field-scale replicated trials evaluated and demonstrated these effects. Sites were monitored for two growing seasons through soil nutrient testing, plant tissue analysis and soil health tests.

Each site was divided into three zones of expected yield productivity with randomized treatments being replicated within each zone. Fertility was variably applied based on yield potential within each zone. All zones were monitored individually. This component adds greatly to the knowledge base on interactions of yield with fertility management and potential phosphorus movement. Additionally, it utilizes the latest technology in precision farming and should allow even further fine tuning of fertility management for optimum sustainability.

Loss of P through surface runoff and leaching is highly correlated to the concentration or saturation level of P in the soil. Baseline fertility levels were established through geo referenced soil testing within each yield zone. Soil fertility levels were monitored throughout the project, at timing intervals related to growth and development of the crop. Tissue samples were taken to quantify phosphate uptake at key growth stages, with crop residue and grain being tested for total and water extractable phosphate (WEP) to measure potential for off target movement. WEP values in crop residue give an indication of phosphorus at risk of off target movement, and evaluations can be made of the impacts of different fertilizer regimes and application strategies on WEP in residues. Yield data and all yield related parameters were collected and analyzed, to add to the evaluations of economic and environmental sustainability implications of the management techniques evaluated.

Results:

The results indicate there is no significant difference in yield between strip tilling and the standard cropping system employed by the cooperators. The yield data indicates there is a significant difference within the various treatments based on the yield potential within the treatment. This means that yield variation observed within this project has a stronger correlation to the factors (soil type and fertility) that influence yield potential over tillage practices. There has also been no significant level of correlation between tillage systems (strip vs cooperator standard) and in the dissolved reactive phosphate in the plant stover. These findings result in the conclusion that strip tillage does not result in a risk of increased dissolved reactive phosphate from fields that adapt strip till cropping techniques. Furthermore this means that the other net positive benefits of strip tillage cropping systems (phosphate fertilizer soil incorporation, disruption of macro pores suspected of causing dissolved reactive phosphate reaching field tile, increase of in season water infiltration by the soil in order that soil erosion is minimized, and the reduction of yield loss due to water ponding from particularly excessive rainfall events) are all achievable with no negative economic impacts or environmental risk from dissolved reactive P. These conclusions have the potential to be significant to primary producers, ag retail, equipment manufacturers, fertilizer manufacturers and the greater Ontario population. 

External Funding Partners:

Growing Forward 2 – A federal-provincial-territorial initiative

Project Related Publications:

None.