Ben Rosser, a corn specialist with Ontario’s provincial agriculture ministry, discussing tillage style and nutrient management in corn with grain farmers during a University of Guelph management seminar in July 2019.


Three ways of getting the most out of your phosphorus


Research projects that analyse the efficiency of repeated heavy P applications and P management in strip-tillage systems highlight more precise agronomic approaches that deliver better yields using less nutrients overall.


BY MATT MCINTOSH A 52


s environmental concerns around nutrient runoff persist, Canadian re- searchers both in and outside the Great Lakes region continue to in-


vestigate how nutrients – namely phosphoros (P) – can be better managed. Here are three examples.


1. Less P, more efficient bioavailability A 20-year study from Canada’s national agricul- ture ministry (Agriculture and Agri-Food Cana- da) indicates that crops growing in soils con-


sistently treated with applied P absorb more than they need. At test sites in the prairie prov- ince of Manitoba, researchers looked at an or- ganic system with no P inputs, an organic sys- tem with a single manure application made in 2007, a conventional system with steady nutri- ent application, as well as restored prairie grassland. Further research with these systems was also conducted in a greenhouse setting (using ryegrass as the plant measure) to better control other influencing factors, such as the presence of weeds.


Overall, results indicate that soil under organic management had lower concentrations of


▶ FUTURE FARMING | 22 May 2020


plant-available P compared with the conventional and grassland soils. Rye grass- centred greenhouse trials showed the biomass uptake from soils receiving no P were signifi- cantly lower for the organic management group. However, it was also observed that P use efficiency increased in the groups with a lower rate of P applications.


Overfeeding makes them lazy Scientist Tandra Fraser says the results indicate that a steady abundance of the nutrient means the soil microbes – which otherwise work to make P available to the crops – have less work to do. Over time this makes them ‘lazy’ and less effective. In the conventional system, Fraser says the rate of plant P absorption was higher – compared to the level of absorption in other systems – despite the same application rates being used. Biomass also didn’t increase with rate of fertiliser in the conventional system.


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