Close eye on research lifts WUE and saves the sheep
GroundCover™ Issue: 111 | 30 Jun 2014 | Author: Nicole Baxter
Adopting a range of practices to improve water infiltration is proving beneficial for the Ingolds near Dirnaseer in southern New South Wales
Derek and Alexander Ingold have implemented a package of practices to maximise water and nitrogen availability on their farm near Dirnaseer, 75 kilometres north-east of Wagga Wagga in southern NSW.
For the past eight years, the father and son have closely watched a study by CSIRO and FarmLink Research investigating the management practices needed to increase grain productivity and whole-farm returns on their 2400-hectare farm.
The GRDC initiated the study in 2008 to challenge growers and researchers across Australia’s southern and western cropping regions to increase grain productivity by 10 per cent.
The study showed water use efficiency (WUE) could be improved by:
- maintaining 70 per cent stubble cover;
- taking a zero-tolerance approach to summer weeds;
- sowing earlier with slow-maturing crops;
- avoiding a build-up of excessive early biomass;
- using break crops; and
- improving the timeliness of operations.
Summer weed control
Starting after harvest, the Ingolds use herbicides to control summer weeds to maximise water and nitrogen availability for following crops.
After the weeds have been controlled, sheep are allowed to graze the stubble, but Derek says this was not always the case. About a decade ago, they stopped grazing sheep on stubble and had started to phase sheep out of their system, believing sheep damaged the soil and reduced water infiltration.
“Initially, I thought the sheep were doing major damage,” Derek says. “You’d put them onto a stubble and within a day or so the soil would be pulverised and powdery.”
So when FarmLink Research received funding from the GRDC as part of the National WUE Initiative, Derek joined the steering committee and encouraged the research team to investigate the effects of grazing sheep on grain returns.
“At the time, I was hoping the study would confirm the sheep lowered our yields so we’d get rid of them,” he says smiling – but it was not meant to be.
The research led by CSIRO’s Dr James Hunt, in collaboration with FarmLink Research, local crop consultants and growers, was undertaken on Peter, Lynne and Jason Coleman’s property, south of Temora, NSW. It showed sheep were not as detrimental as first thought in a well-managed system.
Dr Hunt says the biggest finding was that sheep grazing stubble and crops have no negative impact on grain returns, provided the grazing is well managed, weeds are controlled and 70 per cent of the ground cover (two to three tonnes/ha of cereal stubble) is maintained during the stubble phase.
After seeing the results, Derek is now confident enough to allow his ewes to graze stubble paddocks for two to four weeks in summer and autumn. Putting the ewes on stubble also allows the family’s lambs to be finished on lucerne.
Dr Hunt says the trial results also showed any compaction caused by sheep grazing on stubbles was shallow and transient, usually disappearing after the soil wets again.
“Reduced water infiltration and yield from grazing are due to removal of cover rather than compaction,” he says. “It is sheep’s mouths that do damage, not their hooves.”
Another finding that changed Derek’s opinion on whether to keep sheep was the beneficial effect they had on nutrient recycling.
Dr Hunt says there is a strong possibility that there was more nitrogen measured on plots that had been grazed because of the return of nitrogen through urine, and enhanced solubilisation of organic nitrogen at high pH under heavy urine deposition.
Another benefit, Derek says, was that the findings reinforced his no-tolerance approach to weed control in summer and autumn using herbicides.
To maintain stored soil water and nitrogen for use by crops, the Ingolds are careful to keep paddocks free of weeds until April, when pre-seeding sprays are applied.
Although direct drilling has been used since the early 1980s and no-till with knife points from the late 1990s, the Ingolds bought a 12-metre Boss disc seeder set on 254-millimetre row spacings in 2012 to improve their capacity to sow inter-row early into heavy stubble.
Derek says the main reason for maintaining stubble is to increase rainfall infiltration. The stubble cover also reduces erosion on the Ingolds’ hilly property if heavy storms hit.
To maximise returns through risk management, the Ingolds have zoned their property, with sheep confined to the lower parts of the landscape (where frost is a potential threat to crop yields).
On the low country, lucerne is grown for five to six years, followed by one or two years of grazing wheats, then canola, wheat and back to lucerne.
Lambs are allowed to graze the lucerne until early May before they are put onto grazing wheat and then sold into the export market in July at about 30 to 32 kilograms dressed weight.
The family’s higher country is intensively cropped for about 10 to 15 years, depending on the weed seed burden and soil nitrogen.
Before switching to discs, a Flexi-coil airseeder and bar with knife points and press wheels was used. However, inter-row sowing on the sides of hills proved impossible because the seeding rig would crab sideways.
After one year of using the disc seeder, Derek rates the machine as one of his best investments. A three-metre controlled-traffic system has also been implemented to keep soils soft and friable.
At harvest, crops are cut as high as possible to increase harvest capacity and to avoid having to handle too much residue on the ground at sowing.
To take advantage of efforts made to store soil moisture and nitrogen over summer and autumn, the Ingolds like to sow their grazing wheats early and into weed-free paddocks.
Whylah and EGA Wedgetail are generally sown from 7 to 14 April, allowing them to establish deep roots for tapping into stored moisture and nitrogen later in the growing season. Nitrogen is applied in-crop to match expected soil moisture availability and yield, which is judged through a subscription to the crop-forecasting model Yield Prophet®. This strategy has also helped to avoid building up an excessive amount of biomass early, which can cause crops to run out of moisture for seed set if conditions turn dry.
The threat of herbicide resistance is kept low by applying label rates of herbicide, using triazine-tolerant canola varieties and burning narrow windrows in autumn to destroy any herbicide-resistant weed seeds.
If the weed burden becomes unsustainable on a particular paddock, the Ingolds have the option of rotating it back to lucerne. “Sheep provide a better gross margin than brown manure crops,” Derek says.
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Dr James Hunt,
02 6246 5066,
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