BIG responses to nitrogen fertiliser in canola yields, but none to sulphur, have been the highlights of extensive research conducted for five years at more than 30 sites in the Central West of NSW.
Chief executive officer of Grain Orana Alliance Maurie Street said a GRDC-funded Grower Solutions Group conducting research across the Central West recently released their research findings, gathered at sites as far west as Nyngan to east around Coolah. NSW Department of Primary Industries (DPI) was also involved in the studies. What appears to be quite different to cereals Mr Street said there was no evidence of nitrogen fertiliser leading to premature haying off and reduced yields in dry spring years. There appeared to be a close relationship between greater biomass produced from nitrogen fertiliser and greater yield despite the difficult seasonal conditions.
While soil tests are a good help in making crop fertiliser decisions, Maurie Street said their research noted big canola yield responses to nitrogen in all but those soils testing very high. Even then sometimes responses were economical. Also important for good responses were factors like timely sowing, good weed control and good subsoil stored moisture at sowing. Responses to 50 – 100 kg/nitrogen/ha occurred in most trials but on a number of occasions economic responses occurred with even higher rates, some as high as 1.2 t/ha extra yield. And in the last five years dry hot springs have been a feature of much of the central west. Despite this Mr Street said in many cases if no nitrogen or only small amounts (less than 40kg/ha) were applied a lot of yield loss would have occurred. In many cases increasing applied nitrogen can be the difference between a non-profitable and profitable crop.
Nitrogen timing comparing pre or at sowing application to as late as bud visible as well as split (early plus late) Mr Street said were generally similar, although occasionally slightly favouring pre or sowing application. While overall applied nitrogen resulted in lower oil content (higher protein) Maurie Street said a typical one percent drop required an increase of only 15 kg/ha of yield to compensate, which was easily achieved in the vast majority of cases.
Research conducted in the 1990s showed canola may be extra sensitive to sulfur deficiency but the GOA extensive trialling over many years failed to register any sulphur response.
Next week: Top researchers to update on legume rhizobia studies.
- Bob Freebairn is an agricultural consultant based at Coonabarabran. Email robert.freebairn@bigpond.com or contact (0428) 752 149.
