Abstract
Over the last 20–30 yr, increased intensification and diversity of crop rotations, along with increasingly higher yielding crop cultivars on the Northern Great Plains, has increased nutrient removal from cropping systems, but also increased crop residues returned to the soil, affecting soil nutrient cycling, soil carbon (C) and nutrient balances. The University of Alberta Breton Classical Plots, established in 1929, consist of two crop rotations of varying diversity and intensity: (1) wheat–fallow (WF); and (2) 5 yr, cereal–forage. Superimposed on these rotations are eight fertility treatments, including a check (control), manure, balanced (NPKS), and nutrient exclusion treatments. Soil total C, nitrogen (N), phosphorus (P), potassium (K), and sulfur (S) levels were measured on soil samples (0–15 cm) collected from both rotations in 2013. Wheat yields and N uptake for the 2007–2018 growing seasons from both rotations were compared. In the 5 yr rotation, soil total C, N, and S, wheat yield and wheat N uptake were greater than the WF rotation. Soil total P levels were not different between the two rotations, but soil total K was higher in the WF rotation. Despite higher soil S and comparable soil P, wheat yield and N uptake response to applied P and S was greater in the 5 yr rotation compared with the WF rotation. Response to applied N in the 5 yr rotation was muted because of significant inputs of biologically fixed N. Wheat also responded to applied K in the 5 yr rotation. These results highlight the need to replace exported nutrients.
Highlights
As with so many stories, the details have faded with time
2) When comparing rotations with similar nutrient sources, rotations with perennial legume forages (WOBHH, CF and 8-year) show equal or greater soil C, N, P and S stocks in the surface 15 cm compared to annual grain only crop rotations (CG, WF)
The higher levels of soil organic C in the five-year WOBHH rotation are reflected in higher levels of soil carbohydrates and humic acids compared to the WF rotation.[13,14,4]
Summary
The Breton Plots were established by the Department of Soils at the University of Alberta in 1929. Within the Breton Plots research site, numerous long-term plot experiments have been conducted over the years. This paper summarizes results from the Breton Classical Plots 1980), the Breton Tillage Straw Nitrogen plots 1979) and the Breton Nitrogen Immobilization Plots The experiments were established to find suitable cropping rotations and fertilizer management strategies appropriate for the Gray Wooded soils developed on glacial till in the Breton area of Alberta. Long-term results from the plots show that production challenges on these soils can be addressed with proper nutrient (fertilizer, manure) and residue management and the incorporation of perennial legume forage crops into annual crop rotations
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