Trials conducted as part of the Cooperative Research Centre for Sustainable Rice Production
during 2003-2004 investigated alternative weed management, cultivar assessments and fertiliser
strategies in order to improve the sustainability of organic rice production systems in the NSW
Riverina.
Results indicated there was no immediate rice yield benefit to organic producers by applying any
of the various organic fertilisers tested. Ongoing experimentation may have shown benefits to
cereal or pastures which followed in the rotation, but this was not evaluated. The authors
recommend that organic rice farmers carefully monitor crop yield responses to fertiliser
applications and carefully consider the cost:benefit of fertiliser applications to their cropping and
livestock rotation.
Whilst the yields achieved for organic rice during the experiments were low compared to district
averages for ‘conventionally’ grown rice during the 2003-04 season (yields ranged from 71-86%
of conventional yield), they were well above the 50-75% yield reduction cited as typical for
organically produced rice compared to conventional rice.
The authors recommend that organic rice producers investigate a number of strategies to improve
nutrient cycling within the rice rotation. This includes strategies to maximise symbiotic N fixation
during the pasture phase such as shortening the pasture phase to two years, ensuring a high (at
least 90%) legume component in pastures and improving pasture nutrition (particularly P), water
use efficiency and grazing management. The value of incorporating green manuring within the
farming system to increase N cycling, provide weed breaks and alternative cropping and grazing
opportunities should also be investigated.
Rice establishment techniques (sowing method, fertiliser placement and flushing) may have a
significant impact on N losses and rice yields. Sod-seeding rice into a legume pasture, the method
commonly used by organic producers, is the preferred sowing method for preserving organic
nitrogen as there is zero cultivation and hence slow plant decomposition. Organic farmers can
further reduce N losses during establishment by minimising flushing and by applying organic
fertilisers or composts prior to permanent water (as opposed to sowing application).
There was no statistical evidence that the application of liquid lime and molasses after sowing
prevented the germination of some weeds, and that a homeopathic remedy made out of Barnyard
grass seeds would decrease populations of barnyard grass over time. A field demonstration
showed that harrowing could produce an effective post-emergent control for barnyard grass,
providing the timing of harrowing and soil condition is optimal.