Aglime increases barley yields
Aglime of Australia’s long term field trial program commenced in 1981 and has included results from three barley trials to date. Cooperating farmers managed the trials using their normal farming practice. Yields were measured with a trial plot harvester.
Wongan Hills Trial
Aglime was applied in 1985 at 0, 2.5 and 5 t/ha, each replicated 3 times. The trial was sown to barley that year. Barley yields increased by 0.19 and 0.34t/ha with 2.5 and 5.0 t/ha of Aglime respectively in that first year (figure 1). Topsoil pH was 4.7 in the unlimed soils and rose to 5.5 with 2.5t/ha and 6.1 with 5.0t/ha of Aglime in that season.
Yield increases of this order pay for a substantial part of the cost of liming that is around $25/t at Wongan Hills. Continuing yield increases over the next 15 years or more will ensure large profits from liming. This trial was sown to barley on another occasion with spectacular visual growth increases on limed plots. Unfortunately, yields were not measured. Significant wheat yield increases have been measured regularly on this trial.
Aglime was also applied at 0, 2.5 and 5.0 t/ha rates replicated 3 times on this trial in 1985. At that time the topsoil pH before liming was 4.6.
Unicorn barley was sown in late June 1998, 14 seasons after liming. It yielded 1.65t/ha on the unlimed plots and 2.4 t/ha (0.75t/ha or 70% higher) on the plots that were limed in 1985. This shows that Aglime continues to produce significant profits for a very long time.
Following the initial pH increase after liming, topsoil pH gradually decreased over the next 14 years from around 6.5 to around 4.9. However, midsoil pH increased from 4.2 to around 4.6.
It is possible that even greater responses could have been achieved in this trial if the plots had been relimed with 1t/ha ten years after the initial application to increase the topsoil pH above 5.5 again.
This trial was on deep yellow sandplain that had been farmed under a wheat lupin rotation for many years. Typical topsoil pH’s are 5.0 to 5.5 becoming more acid with depth to 30 or 40cm where pH’s are in the 3.8 to 4.2 range. The pH then rises as depth increases. Aglime was applied in 1988 at 0, 1.25 and 2.50 t/ha rates. The trial was sown to barley in 1992, the 5th season after liming. There was no difference between the 1.25 and 2.50 t/ha rates. Both produced barley yield increases of around 0.3t/ha. The pH levels in 1992 were 5.5, 6.0 and 6.6 with 0, 1.25 and 2.5t/ha Aglime rates respectively.
It was surprising to measure such a large yield increase after liming pH 5.5 topsoil. The yield increase was most likely due to some of the Aglime leaching and treating the very acid subsoil at 10-30cm depth. This would allow roots to penetrate deeper into the soil profile for extra nutrients and moisture.
For best barley yields apply Aglime to bring topsoil pH up to 5.5 and midsoil pH above 4.5. If mid or subsoils need pH correction, topsoil should be limed above pH 5.5 to facilitate Aglime leaching to depth.