Trials on deep grey clay soils near Nindigully, in southwestern Queensland, have shown the potential for healthy profits from applying nitrogen fertiliser to achieve Prime Hard grade wheat and barley for malting-grade crops, even in a relatively dry year.
According to Greg Thomas, Senior Agronomist with the Queensland Department of Natural Resources, the decision about whether to apply fertiliser, and how much to apply, is best made from the nitrate nitrogen (nitrate-N) and soil moisture levels of the paddocks near sowing time.
"In 1996, for example, the soil held 200 mm of available water and 60 kg/ha of nitrate-N at the time of sowing. We added various amounts of nitrogen fertiliser, and found that the more we added, the higher the gross margins were as a result of both increases in wheat grain yield and protein content," says Mr Thomas.
Mr Thomas also believes that the 1997 protein content, which did not make the Prime Hard classification, could have been increased by additional nitrogen fertiliser.
"In 1997, there was 140 mm of soil moisture and 35 kg/ha of soil nitrate-N at the time of sowing, for areas under continuous wheat. As for 1996, we added various amounts of nitrogen fertiliser, and again we found that more fertiliser resulted in greater gross margins." Lower gross margins, grain yield and protein in 1997 compared with 1996 were partly due to the drier 1997 season (117 mm of in-crop rainfall in 1997, 180 mm in 1996).
Yields were particularly low in 1998 due to waterlogging and disease problems associated with the extraordinarily high in-crop rainfall of 500 mm, despite only 120 mm of soil moisture at the time of sowing.
Even so, in wet 1998
"Even with these problems," says Mr Thomas, "profitability increased with fertiliser application because of the higher yield and protein content. In fact, not fertilising would have given a loss for that year, as shown by the negative gross margin." (See Table 1.)
The same can be said of barley, planted after either wheat or another barley crop. Adding nitrogen fertiliser improved profitability, not only because of the increased yield but also because of the higher protein content (see Table 1).
The trials also showed the benefits of including nitrogen-adding crops, such as chickpea, in a cropping rotation. In these trials, chickpea effectively reduced the need for nitrogen fertiliser, giving the yields and gross margins possible for continuous wheat only after intermediate amounts of nitrogen fertiliser (see Tables 1 and 2).
According to Mr Thomas, the benefits of chickpea in the rotation are also obvious for barley. "In 1996, we needed to add 40 kg/ha of nitrogen to produce malting-grade barley. In 1997 we could do this using only the extra nitrogen in the soil from the preceding chickpea crop."
Western Farming Systems project
Supported by growers through the GRDC, the trials at Nindigully and the associated on-farm trials are part of the Western Farming Systems project.
Other outcomes from three years of trials at Nindigully:
- zero-tillage practice for wheat showed larger profits than conventional tillage in average and dry seasons
- faba bean gave inconsistent yield results
- chickpea and faba bean gave moderate nitrogen benefits after legume grain harvests, whereas lucerne and medics grown for 18 months gave good nitrogen benefits
- canola can be profitably grown in this region
- lucerne and medic leys resulted in yield increases in following wheat crops.
The lighter-textured red soils in the area will be studied as part of the next phase of the project, as well as work continuing on the deep grey clay soils.
Contact: Mr Greg Thomas 07 4639 8836
Table 1: Grain yield and grain protein at 12 per cent moisture content and gross margin for 1996,1997 and 1998 winter wheat and barley crops in the farming systems trial at 'Dunkerry South', Nindigully. Prior to fertilising, the soil contained 60,35 and 45 kg/ha of nitrate-N in 1996,1997 and 1998 respectively.
|Crop||N fertiliser added (t/ha)||Grain yield(t/ha)||Grain protein (%)||Gross margin($/ha)||N fertiliser added (t/ha)||Grain yield(t/ha)||Grain protein (%)||Gross margin($/ha)||N fertiliser added (t/ha)||Grain yield(t/ha)||Grain protein (%)||Gross margin($/ha)|
|(following barley or wheat||40||3.68||10.2||450|
Table 2: Grain yield and grain protein at 12 per cent moisture content and gross margin for 1997 and 1998 winter wheat and barley crops after a chickpea crop in the previous year in the farming systems trial at 'Dunkerry South', Nindigully. Prior to fertilising, the soil contained 65 kg/ha of nitrate-N in 1997, for the wheat and barley crops and in 1998 40 kg/ha and 50 kg/ha for the wheat and barley crops respective
|Crop||N fertiliser added (t/ha)||Grain yield(t/ha)||Grain protein (%)||Gross margin($/ha)||N fertiliser added (t/ha)||Grain yield(t/ha)||Grain protein (%)||Gross margin($/ha)|