Sow early for the best yields. That's a short-term measure wheat growers can use to reduce their expenditure on superphosphate if they need to prune costs.
Trials carried out at three sites in southern New South Wales showed that less fertiliser is needed for optimum grain yield in early-sown crops. The results suggest a stopgap measure for reducing expenditure on superphosphate: sow early for the best yields. This strategy has already helped some growers in difficult financial circumstances to reduce their costs.
The downside of the strategy is that soil phosphorus is depleted faster, because the grain of an early-sown crop has a high phosphorus concentration, even when little or no phosphorus is added. Early sowing will bring closer the time when supplementary phosphorus has to be applied to maintain respectable yields. The strategy is a short-term survival approach; it will not work for more than a couple of years.
A very different tack is to sow late in the sowing window (e.g. June) and use high applications of superphosphate to obtain high yields. This crop will produce more grain per unit of phosphorus taken from the soil, as the phosphorus concentration of the grain will be lower. A further point is that the late-applied phosphorus will be of more value to a following pasture.
Growers in high rainfall areas may want to weigh the benefits of the sow-early strategy against the advice that late-sowing helps reduce the impact of barley yellow dwarf virus (see story, page 1).