Legume inoculants and quality control.

Rhizobial inoculants have been used successfully in world agriculture for about 100 years. About 20 million ha crop and pasture legumes are inoculated in the world each year, although that figure could be increased if high-quality inoculants were available to all farmers. The characteristics of a high-quality inoculant relate to the properties of the carrier, the infective (nodulating) and effective (N2 fixing) attributes of the rhizobial strain and the numbers of the strain and other microorganisms (contaminants) that are present in the inoculant. In countries with strict standards for inoculants such as Australia, the carrier (most commonly peat) must contain >109 rhizobia/g and <106 contaminants/g. Other countries demand that inoculants deliver high numbers of rhizobia to the inoculated seed, e.g. 106/seed for soybean in France. Research in a number of countries has shown that the most effective inoculants are produced using a sterile carrier and are relatively fresh, i.e. <6 months old. Rhizobial inoculants lose efficacy with age. The involvement of private-sector institutions in manufacturing and marketing and public-sector in quality control and RD Boonkerd these Proceedings), Bangladesh (Sattar et al. 1997) and Myanmar (Thein and Hein 1997). The Need to Inoculate Although rhizobia seem to be as widely distributed as the legumes themselves, many soils used for legume cultivation do not contain adequate numbers of highly effective rhizobia. They may be devoid of the rhizobia, they may contain low numbers of effective strains or they may contain high numbers of ineffective or partially effective strains. The question 1 NSW Agriculture, Centre for Crop Improvement, Tamworth, NSW 2340, Australia 2 NSW Agriculture, Horticultural Research and Advisory Station, Gosford, NSW 2250, Australia