Physical Aspects of Pastures

7/31/2019 Physical Aspects of Pastures

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Physical Aspects

Mindset of a Pasture Manager

Profit by reducing costs of feed management and manure

management

Rely less on labour and machinery

Allow animals to do their own thing

Challenges for Pasture Manager

Balance forage availability with demand

Fast regrowth during season and long term persistence

Overgrazing = close grazing of preferred species

Undergrazing = undesirable plants left

Plant Recovery Between Grazings

Graze when plants are leafy and nutritious with reasonable yield

Temperature, moisture, fertility

Leaf surface area left after grazing

Amount of CHO stored in plant

When grazing, the most important factor in "quality" of any species

(naturalized or improved) is maturity:

Adequate Plant Rest Periods Before the Next Grazing

Repeated cutting for hay or silage results in a less firm sod for

exercise (higher cutting height than for pasture)


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Repeated close grazing reduces the proportion of some species

(e.g. trefoil, bromegrass, timothy) and total dry matter yield

Adequate rest replaces plant CHO reserves, produces more

surface tea for photosynthesis

Rotational Grazing

Based on the time required for pasture to recover

Length of Rest Period

Spring: 15-20 daysSummer: 30-40 days

System must be flexible

Days of Grazing per Pasture or Paddock

Long enough to graze pasture and short enough to avoid grazing

regrowth

Whole areas grazed quickly and uniformly

Less wastage by trampling and fouling

No opportunity for selective grazing

Most important feature of rotational grazing is period when animals

are not on the pasture allows plants chance to build up CHO

reserves

What are a pasture manager's goal for the plants?

solar energy intercepted

number of leaves per unit area

size of leaves

leaf area/ha

length of growing season

Allow palatable, nutritious plants to compete successfully for

sunlight, H2O and nutrients

Clipping (Mowing)

After removal of animals, clip (mow) to 4-5 cm (1.5 to 2 inches)

Longer for other forages

Remove old forage - stimulate regrowth


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Control weeds, prevents grasses heading

Some dry clippings will be eaten later

Aeration

Dense sod for active horses is like a lawn or playing field - aeration

helps roots

Pastures suffering compaction may benefit from aeration

One commercial aerator has a seeding attachment

Dragging (Harrowing)

Use a chain harrow or link harrow 1x per season

Spreads manure, exposing parasites to sun and air

Manure can decompose quickly, returning organic matter and

nutrients to soil

Effect of Manure on Grazing

Animals avoid grazing plants next to manure

Depending on stocking rate, this can affect 10-45% of the pasture

With higher stocking rate, animals are forced to eat more and more

hoof action breaks up manureAreas between dung pats get overgrazed

Manure Management

Usually do not spread manure on areas to be grazed. If you must,

compost first, then spread thinly.

On small pastures for 1 or 2 horses, some managers pick up

manure daily

Walk, rather than drive your pastures

Check the smoothnessDetect insects and weeds, holes and roughness

Assess the plant growth, vigour, colour, height, species variation

Find hazards; pick up wire and trash

Maintain and Manage that Pasture

Use frequent, close grazing, with high stocking density, for uniform

defoliation

Understocking or under-grazing allows selective grazing of short

favourite plants. allowing tall, less palatable plants to grow, shade

the others and reproduce

Under-grazed plants return apical buds, do not branch out

Overgrazing

Plants are exposed to intensive grazing for extended periods of

time, or without sufficient recovery periods

Reduces the usefulness, productivity, and biodiversity of the land

Leads to spread of undesired plant species

A Balancing Act


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Increasing stocking density allows quick uniform grazing down to

desired plant height

Too high a stocking density = excess trampling damage

Manage: soil fertility, type of plants in high traffic areas, drainage,

to keep animals off fragile areas when wet

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Physical Aspects of Pastures