Which is best for crops? - 60mm in March or 60 mm in September

For Jerramungup this year, September rainfall has roughly equalled the March figure of 60 mm. Which will be more important to wheat yields?
Most people would think the September figure was the important one. But this could be overlooking the important nitrogen release from the March rain. The March rain, followed by chemical fallow has probably contributed a lot to nitrogen release. If this is the case, the theoretical potential of 20 kg of wheat per mm of rain could be adjusted up to 24 kg, according to South Australian researcher, Victor Sadras. For soils with low nitrogen levels, the potential might be as low as 6 kg per mm.
This year's soil tests showed that nitrogen levels were high because it was not just the March rain, but there was earlier rain as well. Consequently, we were expecting good yields, even without the good September rain.
Either way, for this year, crops should yield very well. The question about the benefit from spring rain compared to soil nitrogen levels will be more relevant for future crop management. Most people are at least vaguely aware of the importance of soil nitrogen, but this year's experiences from this harvest will add to this picture.