Farm Table says:
What is the problem?
In the early years of canola cultivation in central NSW crops were often planted after a legume pasture phase where soil N reserves were high.
The evaluation outline to this paper investigates the response of canola to increasing N application combined with mineral N available in the soil at sowing. The results are reported as grain yield and grain oil concentration, as well as the effect on WUE outcomes in the region.
What did the research involve?
Twelve experiments were conducted from 2012 to 2014 at several sites across central NSW (Table 1). Nitrogen rates applied at sowing ranged from nil to 200 kg/ha N and mineral N reserves (at sowing) ranged from 31 to 233 kg/ha (to 90 cm depth).
What were the key findings?
Grain yield and grain oil concentration
• Grain yield responded positively to applied N in 10 of 12 experiments (Figure 1), with a diminishing response in most experiments as applied N rate increased.
Water use efficiency
• Robertson and Kirkegaard (2005) reported on 42 experiments that were managed to achieve maximum yield potential in an equi-seasonal rainfall environment, finding an average WUE of 11 kg/ha.mm.
This combined with knowledge of regional soil N reserves and regional N application practices suggest that WUE outcomes of canola could be improved by increasing N availability to the crop.