“It may be one of the methods that we can help the guys in the heavier clay soils down in the Red River Valley move into a reduced-tillage regime.”
– LINDSAY COULTHARD
It’s hard not to like alfalfa. But Lindsay Coulthard’s feel ings for the nitrogen-fixing legume go a little deeper than most.
During a presentation on the merits of adding alfalfa to crop rotations for participants in the Manitoba Soil Conservation Council of Canada summer tour on July 8, the Manitoba Zero Tillage Research Association farm manager’s voice started to crack.
Someone fetched him a glass of water, and he joked, “When I talk about alfalfa, I get kind of emotional.”
It’s hard not to see why.
A study from 2002-07 at the farm north of Brandon compared a rotation of cereal-pea-canola-cereal-flax-canola with one using three years of alfalfa followed by cereal-flaxcanola.
The results showed that the alfalfa rotation, which was either hayed or grazed with cattle, required less than half as much nitrogen as the one containing peas.
Total N inputs in the annual crop rotation were 373 pounds, versus 142 in its alfalfa-based counterpart. Soil test results showed that after the alfalfa was taken out, the reduced N requirement for the following three years of the rotation averaged 66 lbs./acre with the same yield target.
On the money side, the annual crops paid $213 per acre for an average of $35 per year, while the alfalfa rotation with cattle returned $243 per acre for $40 per year – an extra $5 an acre.
More labour was needed for grazing the alfalfa, but for haying, it was less than annual cropping, and overall less fuel, equipment hours, and chemicals were used.
If future energy costs become increasingly onerous, as some are predicting, the advantage of reduced dependence on natural gas-based fertilizer and diesel fuel might see more farmers adding alfalfa to their rotations.
On the downside, there is greater operational risk from fluctuating hay prices in the diversified rotation. On the other hand, using Alfasure in the water supply helped keep bloat losses at bay.
There is a downside however. Coulthard said haying the alfalfa takes a lot of nutrients out of the soil, which may cost more to replace than the forage is worth.
But with grazing, most of them are dumped right back on the field as manure and urine and cycled back into the soil for the benefit of future crops, he added.
Soil test results comparing the nutrient benefit from either haying or grazing haven’t been completed, but Coulthard is “fairly confident” that grazing will show better results.
The MZTRA farm’s practice of spraying out the alfalfa, then direct seeding into the field instead of discing it in didn’t punish the crop in the following year by drying out the soil, he said.
It also paid off in better water infiltration via the plants’ long taproots, which opened holes for the winter run-off to seep down into the subsoil.
Glyphosate, Amitrol 240 and 2,4-D were used to terminate the alfalfa. Even though the kill rate wasn’t always 100 per cent, he noted that the few remaining plants didn’t compete with the followup crop.
“Including alfalfa as a short-term crop has helped us economically because it has reduced our nutrient requirement and has helped soil quality by adding organic matter,” he said.
In some saline areas, the first attempt at seeding alfalfa encountered problems getting a good catch, but a second run at the rotation in the same spot saw improvements with increased growth into
the salty patches due to better water infiltration.
Evidence of this can be seen in the faster drying of small, ephemeral wetlands, which allows the researchers to crop straight through them.
It may be bad for the ducks, he added, but good for the farmer and the land because the water is being put to productive use.
“The benefits of using alfalfa in a rotation are immense, and we hope to get the word out to producers. It may be one of the methods that we can help the guys in the heavier clay soils down in the Red River Valley move into a reduced tillage regime,” he said. daniel.wint[email protected]