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

Project 22-04 - Dr. Tiequan Zhang

Dr. Tiequan Zhang, Agriculture and Agri-Food Canada - Harrow Research and Development Center

4R Nutrient Stewardship is recognized as essential approach to maximize farming profitability with minimized environmental risk. The current 4R practices have been developed under field conditions where chemical fertilizers (CF) were applied only. However, cropping systems receiving manure have significantly different management requirements than those with CF alone. In manure-amended soils, the fraction of organic N applied that does not mineralize in the year of application accumulates and can have legacy N fertility effects. If manure N residual impacts are ignored in fertilizer decision-making, the soil tends to receive more N than what crops require. Unfortunately, residual manure N has rarely been studied in Ontario on their impacts on soil N availability, based on which chemical fertilizer recommendations are made.

Our studies have characterized phosphorus (P) contained in various Ontario manures and determined manure P fertilizer values using indoor approaches. However, such measured values need to be calibrated and validated under field conditions. Besides adding extra P to the soil, manure application also results in changes in soil P chemistry. These changes tend to reduce amounts of P fixed by the soil and thus enhance soil P availability. Therefore, CF applications based on current recommendations would cause P applied in excess of crop needs in manure-amended soils.

This multi-disciplinary study aims to fill the Ontario-specific knowledge gaps identified above. Based on the new knowledge we will improve/develop CF 4R practices by efficiently utilizing available N and P provided both directly and indirectly by manures previously or currently applied.