Boost crop profitability with soil testing
Author: Ellen McNamara | Date: 02 Feb 2016
Northern region grain growers can maximise the yield potential of this winter’s crop and ensure sustainable, long term land management through strategic soil testing.
Dr Mike Bell, from the University of Queensland’s Alliance for Agriculture and Food Innovation (QAAFI), says soil testing is a key component in ensuring the best possible chance of delivering on water limited yield potential in the coming season.
“Soil testing represents value for money in a farm management plan. Growers’ sampling strategy will be determined by the reasons for sampling – either diagnosis or fertility; selecting an appropriate laboratory test method based on the size and availability of the different pools nutrient in the soil; and working out which soil layers are of interest so that the mobility of the `nutrients of concern’ in the soil profile and the root activity of different rotation species can be monitored,” Dr Bell said.
Dr Bell cautioned that the correct soil sampling strategy and diagnosis of potential nutrient limitations wouldn’t necessarily guarantee a short term economic response to applied fertilizer, as seasonal conditions and inappropriate application strategies can reduce the crop nutrient requirement or limit recovery of the applied nutrient.
However he firmly believes it is growers’ best opportunity to make informed and effective decisions on fertiliser selection and management.
“My most compelling argument for soil testing is that if you don’t understand the fertility status of your soils it is extremely difficult and time-consuming to get the right fertilizer, application rate and method of application to maximise your yield,” he said.
“This is particularly true in the northern region as native fertility levels in our once fertile clay soils have been diminished through grain removal.”
Dr Bell says the northern region has some clear advantages over other rain-fed cropping zones.
“Firstly, moisture stored in the soil profile during a fallow can deliver a significant proportion of our annual crop growth and yield. So once a planting decision is made, questions about crop size and hence nutrient demand are about the extra growth and yield we may derive from forecast in-crop rainfall, rather than whether there will be a crop at all,” he said.
“Secondly, expensive nutrients like phosphorus and potassium often have excellent residual value for seasons following application so we can be flexible about applying them when cash flow and seasonal/stubble condition suit.”
However, the heavier soil types also have some disadvantages, relating mostly to more mobile nutrients like nitrogen and sulphur.
“These nutrients are less mobile in clay soils, meaning they are less likely to be lost below the root zone by leaching. However they are also slower to redistribute into subsoils, where much of the crop root activity occurs, and can suffer loss to the atmosphere as a gas during wet conditions in the case of nitrogen.
“The only practical way to account for these issues, particularly in the case of unusual rainfall events or seasonal conditions on these nutrients is soil testing.”
Prof Mike Bell, QAAFI, UQ
07 5460 1140
Ellen McNamara, Senior Consultant Cox Inall Communications
0429 897 129
GRDC Project Code UQ00063; UQ00078