Field pea magic
Pea magic is the improved yield that can occur for the crop following field peas in rotation.
New Agriculture Canada studies show it is due mainly to the nitrogen contribution of the pulse crop rather than to effects associated with rotations such as reduced severity of pests and diseases.
The information comes from field studies recently completed by researcher Hugh Beckie of Agriculture Canada in Saskatoon.
In previous studies comparing pea rotations to cereal monocultures, the nitrogen contribution of field peas to a following crop was deemed a minor component of the total benefit of this annual legume. Growing cereals continuously on the same land leads to a build-up of pests and disease.
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Nitrogen important
In Beckie’s studies, field pea rotations were compared with mono-cereal, mono-oilseed and mixed cereal-oilseed rotations. Although some nutrient benefit came from field pea residue remaining on the ground after harvest, most came from greater turnover of field pea residue nitrogen (including roots) and soil nitrogen. Field peas made more nitrogen available to the succeeding crop.
In the studies, two-year rotations of field pea-cereal crop (spring wheat or barley) and field pea-flax were compared with non-field pea rotations of flax-wheat, wheat-barley, canola-barley, wheat-flax and canola-flax. Nitrogen fertilizer was applied at incremental rates to the second-year crop.
Best results
Crops grown on field pea stubble generally yielded the highest.
Rotational benefits of field peas were similar to rotational benefits from an oilseed or cereal. The main difference was the nitrogen that peas left behind.
The nutrient benefit of field peas averaged 25 pounds of nitrogen per acre in the black soil zone, but only 11 lbs. in the dark brown soil zone.
To figure how much nitrogen a pea crop left behind, assume 15 lbs. nitrogen per acre for every 1,000 lbs. of seed per acre produced in the black soil zone. This is higher than the recommendation of five to 10 lbs. nitrogen per acre per 1,000 lbs. of seed.
In the dark brown zone, the nitrogen credit of field pea is five lbs. per acre per 1,000 lbs. of seed.
To minimize nitrogen losses to the environment and to maximize profitability, these nitrogen credits should be taken into account when determining how much fertilizer to apply to crops grown on field pea stubble.
– Agriculture Canada
