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Pea-Alfalfa Mix Revives Pasture

John Burden of Lougheed, Alta., says peas perform very well as a take-out crop for depleted pastures. He

direct-seeds peas into the sod and then broadcasts alfalfa seed immediately afterward. He gets a pea crop the first year, meanwhile creating a good foundation for the new alfalfa to get established. Ultimately his goal is to have productive alfalfa stands for hay, silage or grazing.

This report is based on a project I carried out while working with Alberta’s Reduced Tillage Linkages (RTL). I visited Burden’s farm in early May 2009 to observe his sod-seeding operation.

For step one, they used a non-selective herbicide to terminate pasture re-growth after grazing had been done in 2008. Then they direct seeded peas on May 6 followed closely with broadcast seeding of alfalfa. They harrowed then rolled to finish.

The spring season progressed colder and dryer than normal but by July 24, a decent crop of peas was established, along with sufficient plant density and development of the alfalfa.

The Burdens used a Conserva-Pak dual-knife system for seeding peas and a Valmar to broadcast alfalfa.

REDUCED FERTILIZER COSTS

Especially with moisture-stress, depleted grass pasture may never recover sufficiently in response to applied fertilizer. Whereas newly established alfalfa provides premium forage and improved soil quality without the need for nitrogen fertilizer. Additional short and long-term nutrient cycling and other co-benefits can be expected from a crop rotation that includes annual pulse legumes such as peas.

SUSTAINED PRODUCTION

This project demonstrates how the practice of sod seeding allows an efficient, unbroken transition from non-productive pasture into highly utilized perennial forage. For best results, inter-seeding — growing two crops, such as peas and alfalfa, together — must be compatible in terms of:

Weed control strategies. The interseeded crops must have similar available herbicide options. The fall-termination step alone generally provides a weed-free window in sod for early seeding and crop emergence without pre-seed treatments. Burden used Pursuit in crop.

Non-competitive spatial effects. The 12-inch wide row-spacing and narrow knife “furrowed” seed placement of this sod seeding system allows the broadcast alfalfa seed plenty of space for establishment. Post-seed harrowing with land rolling does not compromise the emergence of deep-seeded peas, while finishing the field for favourable alfalfa establishment. Peas root relatively shallow compared to the perennial nature of the multi-branched tap root structure of alfalfa. For this reason, the co-operator prefers the alfalfa variety Beaver and semi-leafless peas.

Harvesting methods. Typically in this system, the peas mature for combining within a natural dry-down season and the clipped alfalfa is ready for winter. Due to the importance of a livestock feed component in the co-operator’s operation, this interseeded crop presents many harvest options. On the Burden farm, the outcome in previous experience has ranged from: High-quality peas in the bin with cows content on the stubble late into fall; feed peas for the hog barns plus baled nutrient-rich residue to supplement the beef herd over winter; or an excellent “salvage” crop of stock-piled silage in the pit as carryover or an extended feed supply, plus the promise of “a place for cows next spring” with a much needed “rest” for stressed pastureland.

REDUCED SOIL EROSION

Burden emphasizes that an “essential” key factor in his sandy erosion-prone soils is conserving moisture with direct seeding. He tried a few variations that achieve similar results in terms of alfalfa establishment — including a companion crop of Clearfield canola — but the risk is greater. Sod seeding peas avoids many of the “discouragements” that he, his father, and his grandfather struggled with in past years.

SUMMARY

Alfalfa established very well as a surface broadcast application with sod seeding, where the minimal soil displacement from the furrows — narrow knife and wide row spacing — was subsequently harrowed and rolled to cover and firm the seedbed while saving moisture.

As a legume, peas grown in terminated pasture offsets much of the nitrogen immobilization that otherwise occurs without an intense amount of tillage to breakdown sod. Peas can withstand deep seeding into cool soils and perform superior, relative to alternative crops, in a period of extended drought, as was shown in 2009 with this project.

Ron Heller is an agronomist, formerly with Alberta’s Reduced Tillage Linkages.

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