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Improving 4R commercial fertilizer nutrient stewardship practices for crop production systems currently or previously receiving manures

Principal Investigator: Tiequan Zhang

Research Institution: Agriculture and Agri-Food Canada

Timeline: April 2022 – July 2027   


  • Calibrate and validate chemical fertilizer nitrogen (N) application rate through, a) determining N availability of  various types (pig, cattle) and forms (solid, liquid) of manure in the year of application and the residue values in the following years with contrasting soil textures; b) determining optimum chemical fertilizer N application rate in the soil with long-term manure application history; and c) quantifying the integrated effects of chemical fertilizer-manure combinations on crop yield and N use efficiency, soil N supply intensity and capacity, organic carbon, and soil N loss.
  • Determine chemical fertilizer phosphorus (P) application rate through, a) field calibration and validation of the lab-determined fertilizer P values of various types and forms of manure; and b) quantifying the effects on crop yields and P use efficiency, soil test P, P sorption strength and capacity, and soil P losses.
  • Develop 4R nutrient stewardship practices for cropping systems currently or previously receiving manure applications to maximize farming profitability and mitigate nutrient loss risks.


  • Improve our understanding of how manure applications influence the intensity and capacity of the soil to provide crop-available N and P.
  • Contribute to the efforts of Ontario (ON) in improving/developing new decision tools for nitrogen and phosphorus recommendations.
  • Provide farmers and crop advisors with data-based 4R practices that also reduce requirements for chemical fertilizer additions.
  • Enable policymakers to make evidence-based guidelines on nutrient management in integrated chemical fertilizer and manure cropping systems.

Scientific Summary:

4R Nutrient Stewardship is essential for maximized profitability with minimized environmental risk. Current 4R practices have been developed under conditions where only chemical fertilizers (CF) were applied. However, manure-amended cropping systems have different management requirements than those receiving CF only. In southwestern ON, an intensive manure-producing area, current 4R practices must be fine-tuned to be suitable to manured systems. The fraction of organic N not mineralizing in the year of application accumulates and can have legacy fertility impacts. Manured soils often contain more organic compounds, which reduce amounts of P fixed by the soil and thus enhance P availability. Unfortunately, current ON fertilizer recommendations do not consider both legacy N effects and enhanced P availability in manured soils. Therefore, resulting CF applications tend to over-fertilize manured soils, risking environmental loss and reducing profitability. We have determined fertilizer P values for Ontario manures using indoor approaches, which need to be validated under field conditions. In addition, current ON recommendations do not consider impacts of soil texture on manure N availability.

This study will evaluate manure N availability in the year of application as well as the residual effects in the following years using two ON soils with contrasting textures, determine optimum N application rates in soils previously receiving manures, and validate N availability under field-based long-term corn-soybean rotation conditions. The study will also validate the lab-determined fertilizer P values of manures using long-term field sites and quantify impacts of manure applications on P availability and optimum fertilizer application rates. To achieve these goals, crop yield, nutrient use efficiency, soil N supply intensity and capacity, soil test P, P sorption strength and capacity, organic carbon, and nutrient losses will be measured. Based on the results, we will develop 4R practices which can be directly and immediately applicable to Ontario grain cropping systems.

External Funding Partners:

Ontario Pork Producers Marketing Board