To uncover what makes for profitable and sustainable crop production.

This study of Victorian wheat crops shows that:

• increasing the uptake of nitrogen by 50kg N/ha improves WUE by 3.4kg/mm,
• introducing a break crop increases WUE by 2.1-4.2kg/mm,
• the efficiency with which fertiliser nitrogen is taken up by wheat increases from 40 to 80% as GSR increases from 200 to 400mm,
• each 1% of OC contributes from 16kg N/ha (200mm GSR to 32kg N/ha (400mm GSR) to the uptake of nitrogen,
• at current prices for fertiliser N ($1kg/N) and for wheat ($170/t) is is still more economic to apply fertiliser N than to increase N supply by raising OC levels with pasture,
• grain protein levels tend to fall by 1% for each 100kg/ha increase in yields.