Research results were encouraging, although a cautionary result was obtained in one field trial. Confirmation was obtained that the microbial strains used in combination in the product have positive effects on the vegetative growth rate and the yield of rice. Yield increases were also demonstrated in a large number of farmer trials, where half a rice farm was treated with a recommended rate of biofertiliser plus a 50 per cent urea application then compared to the other half of the farm that was treated with the normal rate of urea.
In a large number of these farmer trials, yields of about 115 per cent on average were obtained when biofertiliser was applied. Such yields, if consistently obtained, would have clear potential to reduce input costs for farmers, improve total grain yield and possibly provide other benefits.
A similar yield increase from the application of biofertiliser was confirmed in one field trial using a split plot design. The results indicated that lower rates of inoculant biofertiliser would have been sufficient. However, a second trial at a different site using a different rice cultivar with lower rates of biofertiliser application actually showed a slightly negative effect with respect to the rate of biofertiliser application, coupled with a classical positive response to the rate of urea application.
This result in a single trial is not considered surprising. There are other factors involved in delivering an effective result. The biofertiliser product must meet certain quality criteria, and these are currently imperfectly met. Sufficiently high numbers of the most effective microbial strains must be present at inoculation, and in a viable form. Since non-sterile media are used, growth of the correct strain may not always be achieved. Such a cautionary result is not without benefits. Indeed, it justifies the decision to conduct a follow-up AusAID CARD project, focused on quality control of the biofertiliser product.
Laboratory research carried out in Australia has provided support for the efficacy of the biofertiliser product. Field trials in Australia using these Vietnamese strains will require permission from AQIS, which was not possible while questions about their taxonomic identity remained. Identification of the species involved using both nutritional and genetic approaches (PCR and 16s-r-DNA sequencing) now indicates that the three bacterial species (2N, 3C, 4P) selected from the rice rhizosphere for use in the biofertiliser are soil organisms potentially beneficial to the growth of non-leguminous plants. These identifications dispel concerns that the strains might be pathogenic on plants (or humans) and their physiological properties - such as nitrogen fixation, phosphorus solubilisation and phytohormonal effects stimulating plant root growth - are consistent with possible benefits.
All these effects have been observed in laboratory trials. In combination with local Azospirillum and Herbaspirillum strains, the strain known as the 'companion strain' (3C) has stimulated the yield of wheat grown in a typical Australian rice soil not amended with nitrogen or phosphorus fertiliser.