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Deciding to replace a pasture using conventional methods of tillage, annual cropping and re-establishment of perennials is costly, but probably justified where production potential of the annual crops and the new perennial stand is great enough to offset the investment. The cost per acre of removing an existing pasture and re-establishing a new one can easily reach $100/ acre including the cost of seed and equipment (at custom rate values). Reduced carrying capacity as the new pasture establishes adds more costs. If carrying capacity is reduced by 50% or 1.25 animal unit months (AUM)/acre in the year following establishment, the extra cost of lower capacity is just over $30/acre when pasture rates are valued at $25/AUM.
Using herbicides and direct seeding provides some savings compared to traditional methods of plowing and discing. At least one year of annual crop is recommended before re-establishing perennial forage to ensure a proper seedbed for good establishment. Two years of annual crops are often needed to properly break down difficult sod, especially with minimal tillage.
| Example: Savings in harvest and feeding costs help pay for pasture replacement |
| Replacing an old pasture | $/acre |
| Cost of pasture replacement | $ 100 |
| Reduction in grazing days as new pasture establishes | $ 30 |
 | $ 130 |
| Swath Grazing - saving in harvest and feeding costs | $/acre |
| Year 1 | 125 | days @ | $ 0.50 | per day = | $ 63 |
| Year 2 | 175 | days @ | $ 0.50 | per day = | $ 88 |
| $ 150 |
When using herbicides to remove old perennial stands, especially if direct seeding the annual crop, it is important to apply the herbicide in late summer of the year prior to seeding. If the pasture is sprayed in spring, the decomposing sod can interfere with crop development. Applying nitrogen fertilizer helps offset the negative effects of sod breakdown on the crop.
Removing old grass and legume pastures with herbicides and direct seeding annual cereals into the sod saves both money and moisture. However, this method does little to smooth the field. Direct seeding could even make it rougher. Rather than spend more money trying to smooth the field for harvest or damaging equipment by bouncing over rough fields, why not let cows graze the feed in swaths and use that cost saving to help pay for pasture replacement. Studies have shown that savings from reduced harvest and feedout costs when swath grazing are about $0.50/cow/day and a good crop with high utilization can easily yield 150 days of grazing/acre. Over two years of annual cropping, harvest and feedout savings amount to $150/acre. Comparing this figure to the total cost of pasture replacement and reduced carrying capacity of about $130, it appears that swath grazing of annual cereals could have a place in pasture improvement. But remember, the principles of good forage establishment still apply; seed shallow into a good seedbed, limit competition by seeding without a companion crop and clipping, or if using a companion crop, cut the seeding rate by half and harvest early.
Lorne Erickson, Beef/Forage Specialist,
Western Forage Beef Group/AAFRD, Lacombe
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