Farm snapshot - Hinkley mixed farming operation:
- Owners: Matt and Rachel Hinkley
- Location: Derrinallum, Victoria
- Area: 1750ha; 1166ha owned, 583ha leased
- Annual average rainfall: 604 millimetres
- Soil types: Loam over heavy clay
- Soil pH range: 5 to 6
- Crops: Wheat, barley, canola, faba beans, ryegrass/clover hay
- Livestock: 1000 to 1500 prime lambs
A sophisticated system integrating raised beds and on-farm drainage has seen high-rainfall zone (HRZ) growers Matt and Rachel Hinkley build a more resilient, productive and profitable grains operation at Derrinallum, Victoria.
The farming couple, both former agronomists, say a "catastrophic" wet season in 2010 was a watershed moment in the ongoing adaptation of their 1750 hectare-property to high-rainfall cropping in the western districts.
Reflecting on that "turning point" ten years ago, Matt says waterlogging wiped out 70 to 100 per cent of the wheat across half the farm area, then totalling 600 hectares. The surviving crop averaged 1 to 2 tonnes per hectare.
In contrast, wheat planted 'high and dry' on raised beds across the other half of the farm was mostly unscathed, averaging 5t/ha, despite the water inundating paddocks.
This showed that raised beds alone could reduce waterlogging crop losses by about 3t/ha in the HRZ farming system where annual rainfall averages 604 millimetres.
For the Hinkleys, it was a lesson that provided the impetus for a two-year push to implement a complex system of raised beds and drains on the remainder of the farm (then 600ha) from 2011 to 2012.
They had previously developed the raised bed-drainage system more gradually on the other 600ha of the property over a seven-year period from 2003 to 2010.
And the works have continued incrementally on about 550ha of new country (owned and leased) acquired as part of farm expansion in the past eight years.
Matt estimates that altogether, staged over 17 years, the couple has, to date, invested more than $1M in the works to reform and plumb their duplex soil profile, consisting of loam over heavy clay.
In developing the "intricate design" for their integrated strategy, Matt says the central aim was to build more resilient soils that promote optimal crop root growth drawing on improved drainage, aeration, moisture infiltration and microbial activity.
Achieving this objective through transforming the topography and controlling water movement across the soil surface, the couple recouped their capital investment in each stage of the raised bed-drainage works within two years.
Matt says the cost-benefits mainly stem from the reduced waterlogging losses and year-on-year increase in long-term average yields.
Testament to these gains was the 2019-20 season that saw their cereals average 8t/ha, even though the four-month period from May to September was the fourth wettest on record in 79 years. The property received 460mm of growing season rainfall last year.
Matt says the raised bed-drainage system is the main factor contributing to an overall lift in yield potential across their grains program, including wheat, barley, canola and faba beans.
The farm's long-term average wheat yields, for example, have increased about 2t/ha from 4t/ha to 6t/ha in the past eight years since they implemented the system on 1200ha.
The latest works across 270ha this year provide a snapshot of the complexity of the Hinkleys' grand design for raised beds complemented by a series of head, intermediate and tail-drains.
Matt says plans for its design are shaped by detailed topographical mapping on a paddock-by-paddock basis, with the aim of "understanding where water wants to naturally migrate".
This knowledge of water movement over the soil surface informs a blueprint that takes advantage of the existing paddock topography, particularly wetlands, and drain network.
To implement the design on nearly 300ha, a team of three full-time farm operators, including Matt, will apply a four-step process over two to three weeks. He estimates that expenditure on the 2020 works, using their own machinery, is about $200/ha.
It is a process that sees the team use a laser bucket with GPS guidance to reform the paddock surface and relocate excess soil to the centre of headlands. A grading machine is then used to level the soil surface and create tail-drains (v-drains) at headlands. A 12m grader board subsequently refines the smoothness of the soil surface. Finally, a bed-former, which the couple built in conjunction with an engineer, is used to create flat-top raised beds that are 150 to 200mm high, with centres spaced two metres apart.
Once implemented, the raised bed structure is maintained with the bed-forming machine at two to three-year intervals, with emphasis on restoring the seedbed height, which tends to decline 50 to 100mm over two to three seasons. Drains are repaired where necessary as part of annual maintenance works.
The earthworks to develop and maintain the system occur in dry seasonal conditions, usually during February and March before April sowing, in an effort to minimise soil compaction from heavy machinery.
Reflecting on the lessons learnt, Matt says trial and error has highlighted the imperative of "getting the system right where tail-drains are located in paddocks".
This design aspect is crucial since tail-drains or shallow relief drains function to remove surface water from inundated paddock areas. The shallow channels are also the main receptacle for all the water that runs from the paddock into other drains, meaning they underpin the effectiveness of the plumbing custom-built for each paddock.
For instance, experimentation with different types of tail-drains, characterised by variable channel shapes, showed that v-drains were more effective than u-drains (spoon drains) in controlling water flow from cropping country.
Matt says that compared with v-drains, so-called for their v-shaped channel with sloping sides, u-drains have a u-shaped channel with a flat bottom that tends to "collect silt throughout the season, forming internal channels in the drain and obstructing water flow".
They have also switched from flat to domed headlands to better direct water into drains from these machinery turnaround areas at each end of the paddock. Soil is shifted from tail-drains to form the 36m domed headlands, the slope of which helps move water to the paddock perimeter and into the drainage network, he says.
Matt says improved drainage on headlands is an important step in the next phase of the farm's HRZ adaptation since these areas account for roughly 10 per cent of the total cropping area.
He calculates that 40 to 50 per cent crop losses due to waterlogging on 175ha of headland area in wet seasons could be reducing farm business gross margins by about $100,000.
The transition to controlled-traffic farming (CTF) practices was a "natural progression" guided by the rigid structure of the raised beds and drains reticulating their property, Matt says.
"The advances in soil structure due to the combined effect of the raised beds, drainage and controlled-traffic farming are incredible," Matt says. "It has converted structureless, pasty clay into beautiful, chocolate-brown soil that is breaking yield records year-on-year."
To date, they have mostly converted to a 12m, 3:1 CTF system, comprising a 12m header, 36m sprayer, 12m grader board and 36m spreader.
Upgrading from a 10 to 12m seeding bar would complete the 12m configuration of the system, but the Hinkleys are considering this "inevitable" machinery investment against the backdrop of more cost-effective alternatives, such as improved headland drainage.
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More information: Matt Hinkley, 0428 531 731,firstname.lastname@example.org