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Enhancing soil health and phosphorus-use efficiency for crop production with management of organic amendments

Principal Investigator: Paul Voroney

Research Institution: University of Guelph (U of G)

Timeline: April 2019 – March 2024  


  • To determine ability of various organic amendments to complex with nutrients alone and in soils amended with organic amendments.
  • To determine the effects of various organic amendments on the chemistry of phosphorus (P) in calcareous soils.
  • To determine the availability of P to corn and soybeans in calcareous soils amended with various organic amendments relative to that of inorganic P fertilizer.
  • To determine the appropriate soil P test for local calcareous soils treated with various organic amendments compared to that with inorganic P fertilizers for maintaining grain yields, while minimizing risks of runoff P.


  • By providing detailed characteristics of organic matter from various organic amendments and its effects on soil fertility, especially related to soil P chemistry, provide better recommendations for an evidence-based policy to guide farmer’s decisions for soil P fertility management.
  • Produce a comprehensive evaluation of the use of different organic amendments for effective corn and soybean growth in Ontario’s different types of calcareous soils in order to improve recommendations for usage of organic amendments, which will result in reduced P fertilizer costs for farmers.
  • Provide guidance on the use of different soil P test methods for calcareous soils amended with various organic amendments and to estimate P losses from farmlands in order to provide more effective P management in agricultural soils.
  • Provide information on a mechanistic role of various organic matter on soil P chemistry to provide guidance to manage organic matter amendments to soils.

Scientific Summary:

Organic amendments provide both plant-available nutrients and organic matter (OM) to soils for growing corn and soybeans, enhancing soil physical and biological properties and fertility. However, these amendments can be a serious environmental concern when improperly managed, especially phosphorus. Phosphorus-enriched runoff from agricultural land continues to receive attention due to the critical impact P has on water quality. Organic amendments, which typically contain high concentrations of calcium and P in addition to OM, affect soil P chemistry by altering both the amounts and distribution of the various P forms. Recent studies have shown that the presence of OM delays formation of stable P forms in soils. If OM favors the formation of labile P forms over stable P forms in calcareous soils, soil P fixing can be delayed and therefore excess P fertilization should be avoided. While the benefits of OM on soil health are well known, the role of OM in governing soil P chemistry is not well understood.

This project will clarify the mechanistic role of OM on the chemical behavior of soil and fertilizer P by analyzing the capabilities of OM to complex with nutrients including P and determine if OM prevents plant available P from being transformed into stable plant unavailable P forms. It will also investigate how various organic amendments affect corn and soybean growth and soil P chemistry compared to inorganic P fertilizers in both greenhouse and field settings. In addition, Ontario’s current soil P test in soils amended with organic amendments will be validated. The project will also provide critical scientifically-based information for establishing effective P management strategies for agricultural grain production in Ontario, thereby leading to reduced fertilizer costs to  farmers while improving soil health and minimizing the risks of P to water quality.

External Funding Partners:


OMAFRA (2018) New Directions Research Program

We acknowledge the support of the Natural Sciences and Engineering Research Council of Canada (NSERC).