Farm Table says:
What is the problem?
The high rainfall zone (HRZ) of southeastern Australia (500 – 900mm rainfall/year) provides the climatic
environment and soil resources in which canola can yield 3-5 t/ha and wheat can yield 9–11 t/ha with current
Despite these high potentials, the current average yield is only 1-2 t/ha for canola and 2-3 t/ha for wheat, due to abiotic (e.g fertility, waterlogging, subsoil acidity) and biotic (e.g. fungal diseases, insect pests) stresses .
Attaining yields closer to these high potential yields requires additional inputs, and the biggest single cost is fertiliser. Greater understanding is being sought by growers when targeting high yields to reliably predict how much fertiliser to apply.
What did the research involve?
A field survey of soil, tissue and grain conducted in southeast South Australia and southwest Victoria aimed
to establish baseline knowledge about the current nutrient status of soils, and canola and wheat crops in the region.
Soil, tissue and grain samples were taken from commercial crops in southeast South Australia and southwest
Victoria from April to August 2014 with sites ranging from Frances to Inverleigh
The first year of field survey data was also used to identify field sites for nutrient omission experiments that are designed to test the validity of critical soil test values and response curves for high yielding crops in the HRZ.
A second year of sampling was conducted in 2015. This paper presents the findings for the first year.
What were the key findings?
Soil analysis from this first year of field sampling showed that some paddocks in southeast South Australia
had low soil nutrient concentrations for S, Cu, Mn and/or Zn, and this is consistent with earlier surveys
This snapshot of crop nutrient status in the HRZ of southeast Australia suggests that overall plant nutrition
is adequate for current grain yields.
However, there is a broad range of values for some nutrients in soil and tissue, so there are opportunities to improve nutrition for those crops. There was generally no relationship between soil nutrient status and plant nutrient status at the South Australian sites except possibly Cu in tissue.
Future nutrient management research in the HRZ aims to determine the fertiliser strategies needed to meet
nutrient demand when targeting higher grain yields and test the validity of critical nutrient values for high
yielding crops using nutrient omission experiments in the field
Nitrogen fertiliser requirements are generally based on the difference between the nutrients required for a targeted yield and the estimated amount of nutrients supplied from the soil. Balancing N with other essential nutrients such as P, K, S, Cu and Zn is important to attain high grain yields