“By year three, they were getting three times more bales in the fertilized than the non-fertilized field.”
– JANE THORNTON, MAFRI
It costs a lot to renovate an old forage stand. That’s why it’s important to get it right the first time, according to provincial pasture and rangeland specialist Jane Thornton.
But if it’s springtime and you’re just starting to think about tearing up and reseeding a hayfield that is past its prime, you’re already a year behind.
“Producers tend to phone me up in spring because they all of a sudden realize that the stand is not very good,” she said, at a beef production meeting held here recently.
“The better time to be taking it out is in the fall.”
Spraying out growth in spring is a tricky business. Because the plant is drawing on root reserves for growth ahead of the first cut, all the sap is flowing in the opposite direction necessary for a contact herbicide to kill root tissue.
Waiting until there’s eight inches of growth is also problematic, because by the time you get busy seeding, it might be getting too late in the season for a good catch before the first frost. There also tends to be more moisture and residual nitrogen available in the fall.
“Also, if your burnoff in the fall wasn’t good enough, you have time in the spring for a touch-up application,” she said.
A Monsanto study that looked at the efficacy of spring-versus fall-applied Roundup on alfalfa found two litres per acre in fall got a 96 per cent kill rate, while the same amount in spring managed only 53 per cent.
Also, keep in mind that not all glyphosates are created
PLAN AHEAD: Jane Thornton, a MAFRI pasture and rangeland specialist, presents options on renovating old forage stands at a beef production meeting in Lenore.
equal, and the quantity of active ingredient often varies widely. Killing Kentucky bluegrass, also known as June grass, can be particularly difficult without the use of an adjuvant like ammonium sulphate, she noted.
GIVE IT A BREAK
Reseeding alfalfa on alfalfa is a bad idea because the plant’s allelopathic effect suppresses the germination of seeds that are too close. Unless the alfalfa stand has gotten very thin, it’s better to plant a cereal crop for at least one year to give the soil a break.
If you’re using a tandem disk and heavy harrow pulled by a 120-horsepower tractor plus custom herbicide application, the cost of preparing the field prior to seeding could be around $68 per acre. Total costs for taking out a stand, including seed, labour, land and taxes could be as high as $165 per acre. Amortized over a typical six-year lifespan, that amounts to $27.50 per acre.
A three-year trial, done by Roger Sheldon of Manitoba Agriculture, Food and Rural Initiatives in 2008 near Ste. Rose, looking at 10-acre test strips – one fertilized and one unfertilized – found there were big advantages to be had from investing in fertilizer.
Each year, they fertilized to soil test recommendations. In year one, that amounted to 100 pounds of phosphorus, 60 lbs. of potash and 53 lbs. of sulphur. Year two saw them put on 100 lbs. of P and 64 lbs. of K, while year three called for 100 lbs. of P and 111 lbs. of K per acre.
In the first year, 45 1,100-lb. bales were taken off the fertilized areas, versus 24 in the unfertilized strips. In year two, it was 52 bales compared to 20. In year three, yield was 59 bales in the fertilized and just 18 in the unfertilized area.
“By year three, they were getting three times more bales in the fertilized than the non-fertilized field,” said Thornton.
In total, the difference was 94 bales on the 10-acre strips. At 3.28 cents per pound for the hay, and minus the cost of the fertilizer, the net cash gain was $2,021.50.
“So, instead of just saying fertilizer is too expensive, I think it is worth crunching the numbers and maybe doing some strip trials for yourself,” she said. “Establishment costs are high.”
The link between alfalfa winterkill and soil potassium deficiency is well documented, she added. Studies in Manitoba have shown that spreading 100 pounds per acre of K could extend the life of an alfalfa stand by several years.
Cow manure does the same job as commercial fertilizer, Thornton added. Moisture is needed for any kind of fertilizer amendment to work, but once it’s in the ground, it helps plants cope with drought by making them more efficient in their water use.
“You can’t change how much water falls on the ground, but you can change how efficient your plant is in making use of it in converting that water into forage for you,” said Thornton, who’s based at Souris.
“Lack of fertility can actually make your pastures or forage stands appear droughtier than they actually need to be.” [email protected]