Retaining soil water in farming systems using strip/disc machinery 2023
SA Drought Hub – Minnipa Node: Retaining soil water in farming systems using strip/disc machinery DN1_23_02
AIR EP, Buckleboo Farm Improvement Group and SARDI Minnipa Agricultural Centre
Demonstration sites were established in low rainfall farming systems to determine:
- Can we measure increased stored soil water in strip/disc vs conventional no-till knife point systems?
- Are there other measurable benefits to the farming system such as soil cover, nutrition, weeds, disease, yield, soil health measures?
2023 Demonstrations
In 2023 three grower demonstration sites were set up with two different stubble systems, a stripper front stubble system using grower machinery and conventional harvest stubble implemented with the SARDI small plot harvester. The dates of the conventional stubble implementation were Cleve - Bammann 28 March, Buckleboo - Vandeleur 29 March and Minnipa - Oswald 6 April. Ideally the stubbles would have been set up at harvest in 2022, so that any differences in soil water and other measures over summer could have been quantified at the start of the 2023 growing season.
Stubble cuts and stubble height were taken after the stubble treatments were implemented. Soil moisture measurements to 90 cm depth were taken pre-seeding. Spray cards to determine herbicide efficacy and spray coverage in different stubble systems were collected at seeding at Cleve and Buckleboo.
The Cleve site at Bammann’s was sown on 18 April with a NDF SA650 single shoot low disturbance disc system with 24.1 cm row spacing. The paddock with different stubble systems was sown to Hurricane lentils and the stubble was then either rolled or unrolled.
The Buckleboo site at Vandeleur’s was sown on the 4 May with Ballista wheat @ 60 kg/ha with MAP (monoammonium phosphate) @ 60 kg/ha using a 60 foot John Deere 1890 ProSeries Opener disc seeding system with 19 cm spacing, and the MAC conventional 25.5 cm Harrington point seeding system.
Due to the later and dry seeding conditions (Decile 2) at Minnipa, Oswald’s decided not to sow the stripper and conventional stubble demonstration site with a cereal and instead the paddock become a self-regenerating medic pasture. Those project partners decided information relevant to low rainfall farming systems could still be collected with different stubble systems in the medic-based pasture. Half of the medic demonstration area has been fenced off to compare grazed and non-grazed stubble systems.
Average stubble measurements in 2023
| Site | Date | Stubble (t/ha) |
| Cleve (Bammann) | 28 March | 4.4 |
| Buckleboo (Vandeleur) | 29 March | 3.9 |
| Oswald (Minnipa) | 6 April | 3.6 |
Buckleboo (Vandeleur) plant emergence counts (average plants/m2) on 20 June 2023
Stripper Disc Seeding System: 88.1 plants/m2
Conventional Seeding System: 94.2 plants/m2
Minnipa (Oswald) medic plant emergence counts 10 July 2023
| Disc Seeding System
(Average Plants/m2) |
DBS Conventional Seeding System (Average Plants/m2) | |
| Medic plants/m2 | 21.7 | 34.3 |
| Broadleaf weeds/m2
(cape weed, marshmallow, fumitory) |
11
|
17.5 |
The spray cards to determine herbicide efficacy and spray coverage in different stubble systems were collected at seeding at Cleve and Buckleboo, but the spray coverage percentages still need to be processed as does the plant establishment data collected from Cleve (Bammann’s).
Project Conclusions December 2023
Across all sites, the stubble treatments implemented resulted in stripper stubble of 64 +/- 4 cm high and conventional draper front stubble system with stubble of 15 +/- 2 cm high.
Lentil establishment increased in the stripper stubble than conventional stubble at Cleve, however, plant dry matter was higher in the conventional stubble system. The grower’s disc seeder was used to sow into stripper stubble so the conventional system may have had lower seed soil contact.
There were differences in plant establishment at Cleve due to rolling. There were no differences in lentil grain yield due to rolling, however, the benefit at harvest of a flatter soil surface is important. The improved dry matter production of the lentils in the conventional low stubble system followed through to a yield improvement of 0.3 t/ha in 2023. There were no differences in % spray coverage with the different stubble systems using the Miller 7380 with spray air system with a water rate of 45 L/ha used with spray air system to improve penetration into the stubble canopy.
At Buckleboo, the pre-seeding herbicide application had higher spray coverage with the conventional low cut stubble system than the stripper stubble system. There were no differences in wheat establishment, growth, tiller number, grain heads or yield due to the different stubble systems.
Self-regenerating medic at Minnipa established better in the conventional stubble system than the stripper stubble, but there were no differences in dry matter production mid-season. There were more weeds present in the lower stubble system compared to the stripper treatment. Unexpectedly, the spray coverage was highest in the ungrazed high stubble compared to the other systems.
In the 2023, only Buckleboo and not Cleve nor Minnipa had differences with in-crop gravimetric soil moisture content with higher soil moisture in the stripper system compared to the conventional system. Ideally, to test the effect of the additional stubble retained in the stripper system on soil moisture this stubble treatment would have been established and monitored straight after harvest in 2022.
A new project, NGN project “Impact of stripper front and straw length on harvest efficiency, summer weed control, soil moisture retention and pest populations in the Upper Eyre Peninsula” has been funded by GRDC for two seasons. Stripper stubble and two heights of conventional stubble have been implemented directly after harvest in 2023 at Minnipa and Cleve and are ready for the 2024 growing season to monitor the effects of stubble and soil evaporation. This will provide detailed research on soil moisture, measured using in-situ 0-30 cm soil moisture probes over summer in different stubble systems.
Read the full technical report below in Downloads