L4: Rangelands

Strengths, Limitations and Improvement

strengths:

rangelands

-native pastures are adapted to enviro conditions/tolerate poorer soils

-many spp, providing resilience

-perennial native grasses reduce soil erosion, increase water infiltration. ​

-drought-resistant, deep-rooted, and slow soil moisture usage. ​

-control dryland salinity thru deep roots and perenniality. ​

-require minimal or no fertiliser. ​

-fire tolerant: some species thrive under burning regimes. ​

-nutritious when actively growing

limitations:

rangelands

-seasonal dry matter production

-lower herbage quality (protein, ME, P, S, Na) than improved pastures

-fragile under grazing. ​

-low productivity per head and hectare, especially in dry seasons. ​

-limitations vary by rangeland type

in what nutrients are rangelands usually deficient in?

-protein

-ME

-P

-S

-Na⁺

improvements (supplementation):

rangelands

Phosphorus (P) supplementation - wet season (green grass)​

Nitrogen (N) supplementation -dry season (poor dry herbage)

Sodium (Na) and Sulphur (S)

what is a limitation of supplementation?

-v expensive

improvements (tree clearning):

rangelands

-trees compete with grass for soil water

-tree density increases when reduced burning and under grazing ​

-broadscale clearing banned since 2006: strict guidelines apply. ​

-woody regrowth is a major issue after clearing

where is Aus is there a P deficiency?

-most of N. Aus has a severe deficiency

what is a particularly cheap tree clearing method?

-chaining

-however, very destructive

general trend between tree cover (%) and pasture biomass (%)

-as tree cover increases, pasture biomass decreases

limitations:

tree clearing (5)

-woody regrowth

-nutrient decline

-erosion

-salinity (impact on water cycle)

-conservation impacts

How can better grazing management improve rangelands? (Ecograze project)

-Use < 30% of summer growth for long-term capacity (suggest: 25%)

-wet season spelling aids recovery of 3P grasses

-rotational grazing stabilizes pastures better than continuous grazing​

-space water troughs evenly (3 km for sheep, 5 km for cattle)

-avoid overgrazing to prevent erosion, woody regrowth, and weed

-oversow w adapted legume

-replace native grasses

what is the difference between competition and stimulation relationship between trees and pasture?

C: trees inhibit grass growth

S: trees increase grass growth

improvements - advantages:

better animal spp

-intensify animal production

-improve system profitability.

-reduce or remove the need for supplementation.

-higher productivity gives flexibility to meet variety of market requirements.

-more resilient under grazing, reduced degradation.

-rotate with crops and improve soil fertility

why are Mitchell grasses good?

-contain excellent native grasses

• perennial Mitchell grass: Astrebla spp

• annual Flinders grass: Iseilema spp

-could benefit from a legume that can grow on cracking clay soils

• Desmanthus spp

• Caatinga stylo (stylosanthes seabrana)