MOULAMEIN CROPPING GROUP 2016
IMPROVING SOIL STRUCTURE IN SODIC SOILS
AIM:
1. To compare different means of improving soil structure.
2. To decrease the reliance on Gypsum for improving soil structure in sodic soils.
BACKGROUND:
Most soils suitable for rice production in the Moulamein district are moderately-highly sodic and structurally unstable. Commonly Gypsum is applied to improve soil structure and increase crop production potential. However, this is only a short-term solution, requiring repeated applications prior to each cropping season.
To combat this, Moulamein Cropping Group began the ‘Improving Soil Structure in Sodic Soils’ trial. The trial was designed to investigate a number of alternative products which may be able to improve soil structure without the use of Gypsum.
TREATMENTS:
1. Compost: Burn stubble and incorporate A1 Compost at 5t/ha
2. Manure - Stubble: Burn stubble, spread 10t/ha pig manure and rice hulls and incorporate
3. Stubble retained: Mulch stubble and incorporate
4. Manure + Stubble: Spread 10t/ha pig manure and rice hulls and incorporate with stubble
5. Control: Burn stubble and incorporate
6. Standard: Burn stubble, apply 3t/ha Gypsum and incorporate
LOCATION:
The trial was conducted on Michael Chalmers’ property at Noorong, NSW. The selected paddock was a moderately sodic grey clay (Na 9%), which was lasered several years ago. It was sown to rice in 2014 and fallowed until the commencement of this trial.
METHOD:
Ø A cut and fill map was obtained to assess any improvement between soil properties in each zone.
Ø Soil tests for cut and fill areas were taken in September 2015.
Ø Burning of treatments occurred in September.
Ø Incorporation of treatments occurred during the summer fallow.
Ø The paddock was sown to wheat in May 2016.
Ø Yield and protein were recorded using a yield monitor at harvest in January 2017.
Ø Cereal stubble will be incorporated across all treatments in 2017.
RESULTS:
1. Plant establishment
Establishment was highest in the standard treatments. This is to be expected, as gypsum is proven to improve soil structure. Incorporated stubble gave a similar establishment in cut areas but was less effective in fill areas. The rice straw may hav e improved pore space, water infiltration and drainage during establishment.
Figure 2: Plant establishment in wheat across all treatments
2. Yield
The 2016 yield map has been attached.
The standard practice of burning stubble and applying 3t/ha of gypsum gave the highest yield, closely followed by the control treatment of burning stubble and incorporating. Upon further analysis, all treatments which did not retain stubble yielded higher than treatments with incorporated stubble. This is likely to be due to the high carbon content of stubble which leads to nitrogen tie-up in soil.
3. Grain N
Grain nitrogen is a combination of grain yield and protein. This gives an indication of overall nitrogen availability provided by the treatments. The manure – stubble treatment had the highest grain N, followed by the standard practice. This may suggest that additional nitrogen was released from the manure application, which became available after stem elongation, increasing protein levels.
Figure 1: Grain nitrogen content (yield & protein) of all treatments
CONCLUSION:
The standard treatment of gypsum still consistently provided the best establishment and highest yield in the short-term. The application of manure without stubble may provide a more sustained nitrogen source for plant yield and protein, but will not greatly influence establishment.
It is currently unclear whether any of the treatments have altered soil structure. Similar experiments suggest that the addition of manure and compost may take 3-5 years for soil changes to be detected in yield. However, it appears likely that the benefits will still be evident for a number of years after application.
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