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Improving Survival of Sod-Seeded Alfalfa
Establishment success and production of sod-seeded alfalfa can be greatly
improved by killing off the existing sod with herbicide before seeding,
then applying fertilizer with the seed.
Although seeding alfalfa directly into existing grassland is not a new
method of pasture renovation, the practice has not been widely adopted because
the success rate has not always been high. For that reason, traditional
methods of renovating pasture have been favoured over direct seeding.
Disadvantages of Conventional Renovation
The conventional method of pasture renovation usually involves a number
of tillage passes before reseeding. However; there are distinct disadvantages
to this tradition:
- The operation is expensive and time consuming.
- Grazing is severely limited, if not curtailed entirely, during the
renovation period.
- Much of Manitoba's pastureland is stony, saline, on rugged topography,
subject to erosion or a combination of all these.
- Cultivation may be difficult on steep land and exposes the land to
wind and water erosion. Stones and rugged terrain are hard on machinery.
- Tillage dries out the soil. This is particularly critical on dry, coarse-textured
soils.
- A "good catch" is still not guaranteed. In fact, seeding
into dry topsoil created by successive tillage passes is often a
problem.
Direct Seeding Has Advantages
Direct seeding into existing sod is an alternate method of renovating
pastureland. The advantages over conventional methods are many:
- Direct seeding does not expose land to erosion.
- One pass sod-seeding is less expensive than conventional methods of
pasture renovation.
- Rocks are not disturbed and pulled to the surface; wear and tear on
equipment is held to a minimum.
- Soil moisture is conserved.
- Access to rough terrain is easier than with traditional methods.
- Delays in seeding because of unfavourable weather or site conditions
are held to a minimum.
Four Steps to Improved Survival
A recent study by the University of Manitoba's: Plant Science Department
has examined the effect of chemical burnoff of existing sod and application
of fertilizer at seeding on the survival of sod-seeded alfalfa. As a result
of the study, several suggestions for improving the survival of sod-seeded
alfalfa may be made.
1) Spray existing sod with 2.5 l ha (1 L/acre) of glyphosate (Roundup)
prior to seeding. Burnoff can begin in the spring once existing foliage
is growing vigorously and the threat of a killing frost has passed.
2) Inoculate all seed with a viable rhizobia prior to seeding. Always
use registered forage seed, Refer to Seed Manitoba-Variety Recommendations
and Growers Directory for recommended varieties.
3) Use a zero tillage drill or a specialized forage drill to ensure good
seed-to-soil contact.
4) Soil test prior to seeding to determine fertility requirements, then
apply fertilizer as required.
IT'S A FACT
There are approximately 3,575,000 acres of native and 800,000 acres of
tame pastureland in Manitoba for a combined total of more than four million
acres. Total value of production from these lands in 1991 exceeded $300
million. Approximately 13,000 producers use forages in their cropping systems.
Sod Suppression is the Key
Studies conducted by the University of Manitoba's Plant Science Department
have shown that sod suppression and fertilizer use can improve seedling
emergence and survival and dry matter production of sod-seeded alfalfa.
The studies were conducted on two sites, near Gladstone and Portage la Prairie.
Things You Should Know
- The number of alfalfa plants to emerge and survive can be significantly
increased by removing the competition of existing vegetation through non-selective
chemical burnoff before seeding. Dry matter production of alfalfa on burned-off
sod can be increased several times over non-treated land.
- Sod-suppressed sites may exhibit increased dry matter production during
the year following establishment, as well as in the establishment year.
- Soil moisture has a great bearing on the success of sod- seeded alfalfa.
The drier the site, the more important it is to remove the competition
of the existing grasses. Direct seeding helps to conserve whatever moisture
there is.
- Soil fertility also has a direct bearing on the rate of success of
forage establishment. Always soil test your pasture acreage for nutrients,
as well as your crop . Fertilize as required.
- On the sites used for this study, applying 30 or 40 kg hectare of phosphorous
(P(2)O(5)) with the seed improved plant emergence and vigour and increased
dry matter production significantly over non-fertilized plantings. However,
applying 40 kg/ha of phosphorous not increase emergence or dry matter production
significantly over 30 kg/ha.
Table One: Dry Matter Production at Gladstone Site (In kg/ha)
|
1991 |
1992 |
Treatment |
Not
Sprayed |
Sprayed |
Not
Sprayed |
Sprayed |
30 kg ha P(2)O(5) |
776 |
4330 |
336 |
5836 |
40 kg ha P(2)O(5) |
690 |
4765 |
306 |
5115 |
No Treatment |
181 |
2648 |
260 |
5150 |
The dramatic differences in production between the
sprayed and non-sprayed
areas was due primarily to soil moisture factors. Suppressing the existing
sod allowed the alfalfa to take full advantage of the available moisture. |
Table Two: Dry Matter Production at Portage La Prairie (In kg/ha)
|
1991 |
1992 |
Treatment |
Not
Sprayed |
Sprayed |
Not
Sprayed |
Sprayed |
30 kg ha P(2)O(5) |
2563 |
5758 |
2745 |
7732 |
40 kg ha P(2)O(5) |
2612 |
5844 |
3278 |
8400 |
No Treatment |
3073 |
4785 |
2701 |
6577 |
Although alfalfa establishment on the non-sprayed sites
was satisfactory,
suppressing the sod more than doubled production. |
Table Three: Dry Matter Production in Year Following Establishment
(in kg/ha)
|
GLADSTONE |
PORTAGE |
Treatment |
Not
Sprayed |
Sprayed |
Not
Sprayed |
Sprayed |
30 kg ha P(2)O(5) |
2068 |
2218 |
7881 |
8741 |
40 kg ha P(2)O(5) |
1018 |
2352 |
7186 |
7041 |
No Treatment |
627 |
1722 |
6531 |
8061 |
The effects of sod suppression and fertilizer in the year
following establishment
are evident but far less dramatic. |
|