Factsheet #4 – June 2003
Dr. Victor Sadras – Research Scientist, Farming Systems CSIRO
Everybody knows that water supply constrains yields in the Mallee. But what goes on in the field is complex, and single factors rarely limit crop yield.
• Focus paddock data across the Mallee indicates that wheat yields fall by an average 17kg per hectare per day if sowing is delayed from mid April onwards.
• Low levels of organic matter in the soil and low rates of nitrogen fertiliser often lead to shortage of nitrogen in cereal and oilseed crops.
• Low availability of phosphorous and micronutrients are common in Mallee soils.
Late sowing, shortage of mineral nutrients, weeds and diseases, and water availability, among other factors, thus constrain crop yield. Therefore, the bottom line is that many crops in the Mallee do not reach their attainable yield as determined by water availability (see Figure 1).