Trials near Katanning in Western Australia have shown that growers may see increased yields in the first cropping year after lucerne after a spring removal of the pasture, but the nitrogen benefits from lucerne compared with a subcloirer pasture do not appear to last any longer than two years.
According to Roy Latta, Senior Research Officer with Agriculture WA, the increased yields for the first two years reflect the higher levels of available nitrogen from lucerne pastures.
"In the third year, however, there was no longer any more nitrogen from the preceding lucerne pasture than would have been available from a subclover pasture," said Mr Latta.
Wheat grain protein levels tended to follow a similar pattern to crop yields and available nitrogen, with the extra benefit of lucerne over subclover lasting only two ears.
One explanation offered by Mr Latta is the possibility of more rapid mineralisation of nitrogen from lucerne roots, which is, then rapidly leached out of the soils, particularly during a wet summer.
The Katanning trials also looked at the relative benefits of pastures dominated by annual grasses, and found that crop yields, were down in all three years compared to the lucerne and subclover dominant pastures.
Contact: Mr Roy Latta 08 9821 3333