Store soil water to help close the yield gap
GroundCover™ Issue: 120 | Author: Cox Inall Communications
These top operators typically have finely tuned farming systems and make timely agronomy and management decisions.
This is allowing them to close the gap between their potential and actual crop yields, according to farm consultant Simon Fritsch of Agripath, based in Tamworth, New South Wales.
He says a big driver of yield is employing systems and practices that store out-of-season rainfall in the soil and convert it efficiently – along with in-season rainfall – to grain.
Investigating ways to improve crop water use efficiency (WUE) is a key focus of the GRDC ‘Economics of Closing the Yield Gap in the Northern Grains Region’ project.
Through this project, Mr Fritsch is assessing WUE benchmarks, which he says underpin crop yield estimates for a specific location and season and can be used to monitor yield trends over time.
He says new tools and technologies, such as CliMate and electromagnetic soil mapping (EM38), can improve the accuracy of WUE benchmarks by including estimates of stored soil water and potential crop yield.
“In extremely low-yielding situations, the crop has used a lot of the available water growing to the flowering stage and the WUE can be less than a half of the WUE of a high-yielding crop,” he says.
“As yield potential improves, there is generally better tiller survival, more heads per hectare, more grains per head and higher grain weights – which improves WUE.”
Data collected by Agripath from trials and farm benchmarking in north-eastern NSW and south-east Queensland have found WUE in wheat can increase from about nine kilograms per hectare per millimetre of rainfall when crop yields are less than 3 tonnes/ha, to 12kg/ha/mm when yields are between 3 and 4t/ha.
Mr Fritsch says WUE in these areas can be routinely above 15kg/ha/mm when wheat yields exceed 4t/ha due to a favourable season.
He says the accuracy and usefulness of using WUE benchmarks to estimate crop yields can be further improved by using a range of estimates, such as 9, 12 and 15kg/ha/mm – depending on yield potential, and accounting for sowing time.
For example, if the WUE for wheat planted in mid-May is 15kg/ha/mm, it will fall by about five per cent each week and would be only 12kg/ha/mm for wheat planted in mid-June.
Mr Fritsch says to optimise crop yields for 2016, it is important to pay attention to crop variety choice and rotations, input spending, control of weeds, diseases and pests, soil health, stubble cover and fallow management.
He says good management practices may be able to conserve an extra 20mm of stored soil moisture, which can produce 0.4t/ha in extra wheat yields. In some cases this is enough to double profits.
Mr Fritsch says in some lower-rainfall areas, a high frequency of lower-yielding crops with small margins may be less profitable to grow than a well-planned rotation that includes some crops grown on long fallow during the change between summer and winter cropping.
“Good margins are important and, in some cases, too much opportunity cropping can result in reduced margins over the longer term,” he says.
More information:Simon Fritsch, Agripath,
0428 638 501,
2015 GRDC Grains Research Updates papers
End of Ground Cover issue 120 (Northern edition)
Read the accompanying Ground Cover Supplement:
GRDC Project Code APT00001