Crop yields varied by year in this study but on average, MP yielded 10% more corn and 13% more soybeans than CT. Linear relationships were established between soil available P and cumulative P budgets obtained under MP or 0 kg P ha −1 under CT. The N and P fertilization increased the availability of these nutrients, but had no significant effect on the soil microbial biomass, activity, and structure. However, soil N 2O emissions were not affected by tillage. The MP practice resulted in greater organic C content deeper, near the bottom of the plow layer, which promoted soil microbial activity at that depth. Results obtained 12 to 20 yr after initiation of the study indicated that CT enhanced organic C accumulation, NO 3-N, P and K availability, microbial biomass and activity, and microbial community structure in the upper soil layer, likely due to leaving crop residues at the soil surface. Soil tillage was performed every year while synthetic fertilizers were applied only to the corn. A long-term field experiment was initiated in 1992 at L'Acadie in southern Quebec on a clay loam soil to evaluate the effect of tillage, synthetic N fertilization (0, 80, and 160 kg N ha −1) and synthetic P fertilization (0, 17.5, and 35 kg P ha −1) on soil functioning and grain yields of a corn–soybean rotation. Adoption of conservation practices can induce beneficial changes to soil properties and related crop yields in which magnitude varies according to soil and climatic conditions but usually increases with time.

Long-term tillage and synthetic fertilization affect soil functioning and crop yields in a corn–soybean rotation in eastern Canada.

A., Gagnon, B., Lalande, R., Morel, C., Rochette, P.

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