Organic Rice Production – Improving System Sustainability

Abstract

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.