THE most frustrating aspect of cropping must be to have knowledge that you've got subsoil moisture you can't access.
That's the case on Pindar farmer Mark Flannagan's property where he annually establishes 8100 hectares (20,000ac) of mainly wheat.
The property is marked as a 300mm rainfall zone on maps but this year he has recorded 210mm, with 100mm of that falling in August, the month that saved the bacon of many northern Wheatbelt farmers.
The immediate response is to discuss the lack of subsoil moisture, based on the hypothesis that no summer rain plus 210mm, from April, equals no subsoil moisture.
Well take a close look at the soil core test picture on this page to explode that hypothesis.
What Mark discovered two weeks ago was that at a 40cm (16in) depth, when soil core testing was done, unused moisture was clearly visible and showing as shallow as 20-30cm (8-12in).
This indicated that the wheat roots could not access that moisture due to a physical (chemical) constraint restricting growth.
This year Mark is resigned to harvesting crops that will probably average between 1.4t/ha and 1.6t/ha.
While this is above his budgeted 1.3t/ha, clearly if crops had access to that unused moisture, he would have been looking at a far different and more profitable scenario.
The latter is the subject of a collaborative research effort involving farmers, the North East Farming Futures Group, the Agriculture and Food Department, Birchip Cropping Group and Geraldton-based Agrarian Management, seeking to quantify a better management risk for growing crops in low rainfall areas.
This year Mark earmarked a 450ha (1100ac) block for the research group to mainly assess the merits of EM38 and radiometrics technology, integrated with the Yield Prophet model.
The idea was initiated by Craig, in an effort to develop a method of mapping soil water-holding capacity across a property.
EM38 involves electro-magnetic (EM) and radio-metric technology to identify the variation in soil types across a paddock.
This is then integrated with historical paddock yield maps to implement variable rate inputs to enable a more accurate allocation of input dollars to production reliability.
Yield Prophet is an on-line crop production model designed to provide grain growers with real-time information about the crop during growth.
To assist in management decisions, growers enter inputs at any time during the season to generate reports of projected yield outcomes showing the impact of crop type and variety, sowing time, nitrogen fertiliser and irrigation.
Obviously moisture is the key, so it is important to identify the sorts of "buckets" farmers have underneath different paddocks, capable of holding moisture for access by crop roots.
In this discovery process, using EM38 particularly, often restraints to root growth are discovered and on Mark's farm he knows he has an aluminium toxicity problem measured around 30cm (12in) below the soil surface.
"I've got 1.4m (56in) of soil depth, which fills with moisture like a bucket," he said. "But crop roots can't access it because root tips are burnt by chemicals at 30cm, effectively stopping them from pushing deeper into the soil profile.
"So using EM38, we identify the problem and make a decision, either to stop cropping the area or rip lime into it to ameliorate the soil and neutralise the aluminium toxicity so we can continue cropping.
"That's what I call managing risk.
"We've got technology and tools to help us identify high and low profit areas of the farm and then we employ people like Agrarian Management who can do the interpretive analysis which can help us understand predictive patterns.
"This means using inputs more efficiently and spending money more wisely.
"The Yield Prophet trials range from the poorest to best soils and we want to identify moisture-holding capacity and see if it is measurable during the year.
"That will enable us to make a more informed decision on whether or not, for example, we make a urea application."
It is the sort of predictive information Mark hopes will show out in the trials on his property.
"There's no problem visually identifying poorer-producing patches of land but identifying the reason is a far different story where you need tools like EM38 and Yield Prophet and the interpretative skills," he said.
"Before we started becoming involved in this research, it was really a matter of throwing money at problems and in effect taking more risk by investing in non-performing areas.
"But now we are getting information from EM38 and Yield Prophet, we are better placed and more confident of making investment decisions."
Mark admits the information comprises "a lot of science" and he is happy to have Agrarian Management on-board to help him make sense of all the data he collects.
"We're moving towards variable rate product applications as Agrarian helps us with our prescription maps," he said. "I see variable rate as another tool to help us with our risk management."
Mark will keep the trial going for at least another two years to identify the management practices he wants to adopt for his cropping program.
"It's a bit of suck and see at the moment but at the same time it is exciting to be involved in something at the cutting edge," he said.
"There's no doubt if it all comes together, we will have the ability to manage risk in a low rainfall area and make profits."
His gut feeling on yield potential on his land is "a lot more than we're getting now".
"The highest we've yielded is 6t/ha on good patches of soil and that really is the carrot to look at doing things differently," he said. "We're learning so much more now and the key is flexibility to play the seasons.
"I'm confident we can reach the stage where we have enough predictive information that tells us to ratchet up post-sowing nutrition applications or back off because there's no point.
"We're passed the stage of pumping crops because the season might turn out okay.
"What this trial work essentially will reveal is that guesswork is not the best tool to employ to manage risk.
"If you think about it, we can make more money out here for less risk in a perceived high risk low rainfall area than some people farming in a safer rainfall area."
But it's not all science.
Another interesting aspect of farming in low rainfall areas is the trend towards chemical fallows to preserve moisture for the following year's crop.
The strategy is to "bomb" selected paddocks in June with 1L/ha of glyphosate to kill mainly germinating ryegrass and radish plants.
While subsequent rains will spawn new germinations, a second "hit" in September can clean up paddocks.
"It's basically two cheap sprays with the reward of keeping moisture in the ground the following year," Mark said.
Last year Mark chemical fallowed 6500ha (16,000ac) of land earmarked for this year's cropping program and it maybe a subject of conjecture, but those soil core tests could be the proof that unused moisture from the previous year hangs around if you have a "bucket".
The threat of chemical resistance is acknowledged but Mark sees that issue as a "manageable problem".
"It's basically the old integrated weed management," he said. "Rotation of chemicals, rotations of crops, ploughed fallows or chaining.
"Another tool is windrowing chaff at harvest and burning the windrows to kill weed seeds."
Chemical resistant weeds are around and Mark found a patch of resistant ryegrass on his property last year.
"It's not a great worry to me and we're finding that higher rates of chemical will kill the rye."
According to Agrarian Management agronomist Craig Topham, the collaborative research effort assessing EM38 and Yield Prophet is at the cutting edge of agricultural research.
"Everybody involved in this trial is on a learning curve which will have positive impacts, particularly for growing crops in low rainfall areas," he said. "Our involvement is interpreting data to allow informed management decisions that can improve soil health and/or increase cropping efficiency and overall enterprise profit."
According to Craig, soil testing is an integral part of employing EM38 and radio metrics.
"Ground truthing is absolutely essential," he said. "Information using EM38 is directive so it needs to be integrated with digging soil pits and analysing soil core tests.
"It's the same scenario using radio metrics," he said. "You can finish with a nice map showing variability but the key is to discover what drives that variability and how that variability affects plant productivity," he said.
This is where the skill to interpret maps can influence that variability.
"We may encounter a nutritional problem or a physical one, such as soil pH, aluminium toxicity or simply water-holding capacity," Craig said.
"The area identified may require a soil ameliorant, additional nutrient supply, or it could be economic to employ a practice such as spading, claying or mouldboard ploughing, for example.
"We are developing virtual paddocks within paddocks that can be managed according to their production reliability.
"This 'virtual fence line' within a paddock, separates the safe investment from the risky investment, thus allowing the farmer to increase his exposure to the safe investment and decrease exposure to the risky investment."
