Lecture 5 - Strengths, Limitations + Improvements of Rangelands

Strengths of Rangelands (part 1)

1. Native pastures are adapted to prevailing environmental conditions and more tolerant of poorer soils.

2. Often comprise many species, which provides a level of resilience.

3. Perennial native grasses provide a permanent ground cover and play an invaluable role in reducing soil erosion and increasing water infiltration.

4. Often drought resistant, deep-rooted and can draw on moisture reserves from deep in the soil profile.

5. Soil moisture is used by some native species at a slower rate than exotic grasses.

Strengths of Rangelands (part 2)

6. Some native grasses can also help control dryland salinity, due to their deep root systems, summer activity and perenniality, reducing recharge to ground water.

7. Minimal or no fertiliser is needed by native grass species.

8. Generally tolerant of fires and some native species proliferate under semi-regular burning regimes (e.g. Heteropogon contortus – black speargrass).

9. Can be nutritious when actively growing.

Limitations of Rangelands

• Seasonal dry matter production.

• Generally lower herbage quality (protein, ME, P, S, Na) than improved pasture species.

• Fragility under grazing.

• Productivity low per head, and per hectare, especially in dry season.

• Degree of limitation varies with rangeland type.

Nutrient Status of Rangelands

• Good spike of nutrients when pasture is young + healthy + vegetatively growing, but as pasture starts to mature, it comes with a decrease in nutrients

• So with maturity of pasture comes a decrease in proteins, nitrogen, phosphorus

Seasonal Production limitations of rangelands

• drier periods - decrease in pasture productivity (not as nutritious)

• A cyclical effect (“sore tooth effect”) - where live weight of animals increase, decrease, increase, decrease, etc

• Ideally would just want to have a linear line instead of the up down up down

How do you prevent the decreases in liveweight of cattle

• add improved pasture species (putting legumes into the pasture will give more nutrition for a longer amount of time)

• Feeding Supplements (like protein supplements)

Describe what occurs for the animals in poor native pasture, good native pasture vs good improved pasture

Poor native pasture

• takes quite a while for the animal to reach the market weight

Good native pasture

• mitchell grasslands + black speargrass country are examples

• there are more markets to access

• Animal is getting fed some extra grain or forage for a period of time

Good improved pasture

• animals are growing faster

• animals are turned off at a younger age

• more markets for landholders to sell their products to

What are some improvements of rangelands that can be made

• Supplementation

• Tree Removal (trees compete for resources but also they can provide shade)

• Improved grazing management

• Improved species

Supplementation

• can improve liveweight gain

• Phosphorus in wet season while grass is green

• Nitrogen in dry season to improve grazing of poor dry herbage

• Sodium + Sulphur are often necessary any time

• Use of supplements is expensive so it’s important to know if it will benefit the specific animals in the pasture and to know what time to use them

What is the biggest limiting nutrient?

Phosphorus!

• most of our soil has very little phosphorus

• Phosphorus supplements is very common by landowners in Northern Australia

Do these cows receive phosphorus supplement?

No! These cows are on a native pasture that is low on phosphorus soil and do NOT receive phosphorus supplementation

• These are skinny cows

Do these cows receive phosphorus supplement?

Yes! These cows are on the same low phosphorus soil native pasture but they RECEIVE phosphorus supplementation

• Better weight

Tree Clearing

• Trees can reduce grass growth due to competition for soil water.

• Tree density in many native pastures increased since advent of ruminant grazing and reduced burning (aboriginals burnt regularly).

• Currently strict clearing guidelines and permission required.

• Broadscale clearing of remnant vegetation banned from 2006.

• Woody regrowth can be a major problem after clearing, especially if overgrazing and no burning.

What was a common practice/was cheapest method of tree clearing?

Chaining

What is the generalized relation of pasture biomass with tree cover?

• An increase in trees would lead to a decrease in pasture biomass

• The trees can have a competitive or stimulatory effect on pasture

• More of a competitive effect where tree is competing with pasture for resources

• The stimulatory effect is from when a few trees can provide shade for livestock + stimulates pasture growth by putting nutrients into the ground (dropping all their leaves) and some grasses like shade

What was a vegetative community that had a high potential area that has been cleared a lot and has become very productive and supports most of improved pastures?

Brigalow!

What are some risks of clearing/thinning woodland vegetation?

• Lack of response to clearing or thinning

• Regrowth problems (tress just keep coming back)

• Nutrient decline

• Erosion risk (tree roots may have been holding the soil together)

• Impact on the water cycle and the risk of salinity

• Effects of conservation of native plants and animals

Why return trees to landscape to create a woodland environment?

• Nutrient cycling

• Shade for animals

• Habitat for fauna

• Carbon sequestration

• Secondary income

Better Grazing Management - level of utilization

• Make sure stocking rate is appropriate to amount of pasture

• Long-term carrying capacity achieved if grazers use less than 30% of summer growth (allows for 70% of pasture to protect soil and put nutrients back in)

• Heavy stocking weakens the perennial grasses, causing erosion, woody regrowth, ingress of weeds

• Rangelands frequently overgrazed, especially during dry times

What is most important management tool for grazing management?

• Stocking Rate

Ecograze Project

• suggests 25% utilization of pasture overall, but if there are times you can provide a bit of rest for your pastures, there could be times where you could utilize the pasture more heavily (so 50% utilization then give the pastures a spell)

• Early wet season spelling (then increase utilization rates to 50%)

• Wet season spelling is important for the recovery of 3P grasses

• Need to have more paddocks so that the paddocks can be rotationally spelled in early wet season

• can increase cash flow

More Better Grazing Management ideas

• Rotational grazing or cell grazing for pasture stability rather than continuous grazing

• Use fences to separate resilient and non-resilient, preferred and non-preferred pasture types

• Space water troughs to give more even grazing (within 3km for sheep and 5km for cattle)

• Oversow with an adapted legume

• Replace the native grasses as well

What are the advantages of using better species

• Intensify animal production

• Improve system profitability

• Reduce or remove the need for supplementation

• Higher productivity gives flexibility to meet a variety of market requirements

• More resilient under grazing, reduced degradation

• Rotate with crops + improve soil fertility

What is one native pasture community that already contains excellent native pasture and doesn’t need much improvement?

Mitchell Grasslands

• Perennial Mitchell grasses (Astrebla spp.)

• Annual Flinders grass (Iseilema spp.)

• Could benefit from an introduction of a legume that can grow on cracking clay soils (has not been any options until recent introduction of Desmanthus spp. and Caatinga stylo

Examples of pastures with improved species

• Cleared Brigalow replaced with buffel grass to give better growth (Leucaena paired with buffel grass)

• Cleared rangelands replaced with Rhodes grass

• Cleared areas in southeast QLD replaced with Rhodes grass/villose joint vetch