10. sustainability

Question 1

The production of one tonne of grain results in the loss of

Answer 1

7 tons of topsoil on average

Question 2

organic carbon content of surface soils in Australia has decreased by between

Answer 2

50-80% since european arrival

Question 3

The grazing value ($/ha) generated from the cover crop in central NSW compensated for the grain yield reduction, True or False?

Answer 3

True

Question 4

benefits of summer cover crops in central NSW (5)

Answer 4

• reduced wind erosion
• cooler and more consistent soil temperatures
• less herbicide applications over the summer fallow
• forage value from grazing
• potentially increasing total carbon percentage

Question 5

Cons of summer cover crops in central NSW (5)

Answer 5

• reduced nitrogen levels
• reduced grain yield
• higher risk of soil water deficit
• potentially increasing disease risk in the following years cash crop
• patchy establishment

Question 6

Appropriate tactical use of summer cover crops may arise in situations where (3)

Answer 6

• soil cover is reduced by winter crop failure or prolonged drought creating significant erosion risk
• recalcitrant herbicide resistant weeds in winter crops require a chemical spring fallow and summer cover/forage crop, which could be grazed
• full soil profiles at harvest and wet seasonal outlook provide opportunities for cover crop growth without significant pre-emptive competition

Question 7

is widespread cover crop use compelling enough?

Answer 7

The rationale for widespread summer cover crop use in southern Australia is currently not compelling without more evidence for the scale and mechanisms of the anticipated benefits.