Rhizobia were isolated from nodules off a stand ofLotus corniculatus established with a single inoculant strain, ICMP3153, 7 years earlier in an area devoid of naturalized Rhizobium loti. The isolates showed diversity in growth rate, Spe I fingerprint of genomic DNA, and hybridization pattern to genomic DNA probes. The 19%o of isolates that grew at the same rate as strain ICMP3153 were the only isolates that had the same fingerprint as strain ICMP3153. Sequencing of part of the 16S rRNA gene of several diverse isolates confirmed that they were not derived from the inoculant strain. Nevertheless, all non-ICMP3153 strains gave EcoRI and Spe I hybridization patterns identical to ICMP3153 when hybridized to nodulation gene cosmids. Hybridization of digests generated by the very rare cutting enzyme Swa I revealed that the symbiotic DNA region (at least 105 kb) was chromosomally integrated in the strains. The results suggest that the diverse strains arose by transfer of chromosomal symbiotic genes from ICMP3153 to nonsymbiotic rhizobia in the environment.

This paper reviews the requirement for inoculation of white clover (Trifolium repens) seed with rhizobia bacteria in New Zealand. The pastoral industry relies on the nitrogen fixed by clover's rhizobia bacteria. These rhizobia were not present in soils prior to European settlement, but were introduced as contaminants, and naturally spread with pastoral development. The advent of large scale land development in the 1950s identified areas where clovers failed to nodulate and establish due to the absence of rhizobia, which led to the development of inoculated lime coated seed. Rhizobia have spread widely throughout New Zealand, and in the great majority of situations where pasture is being sown, soils now contain high levels of resident rhizobia capable of nodulating white, red and alsike clover, and inoculation of clover seed is not required. However, it is suggested the use of inoculated clover seed should be considered in the following three situations as an insurance against nodulation failure: undeveloped grasslands with no evidence of resident clover; virgin pastoral land cleared directly from scrub; and paddocks cropped with maize continually for over 10 years. It has been hypothesised that inoculating clover seed may improve clover growth through introducing more effective rhizobia with better nitrogen fixation ability, but the research in this area suggests there is little likelihood of any significant response from doing this. Keywords: rhizobia, inoculation, coated seed, white clover, red clover, alsike clover

Locally applicable information about climate and soil properties can help farmers identify opportunities and reduce risks associated with changing to new land uses. This article describes techniques for preparing high-resolution regional maps and GIS

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The interactions of lime, seed pelleting, and inoculation level were investigated on white clover (Trifolium repens) growing on a range of soils in the glasshouse.In the absence of seed pelleting, the addition of 2500 kg/ha of lime markedly increased the growth of clover on soils of low pH (4.7-5.0). The same effect was produced in the absence of lime by pclleting the seed (with lime or Gafsa-phosphate + dolomite). The increase m plant growth from lime or pelleting accompanied an increase in nodulation on one soil {pH 4.9) where nodulation was investigated. Lime or pelleting increased both crown (within 1 em of soil surface) and distal (remainder) nodules.On soils of pH 5.3-5.5, lime and pelletin~ effects were variable and less marked than al lower pH. Pelleting either had no effect or increased clover growth, whereas the effect of lime ranged from depression to enhancement. At pH 6.2, both lime and pelleting depressed growth.On two soils (pH 5.0 and 5.4), increasing the inoculation level from 2 X 103 to 2 x 104 rhizobia per seed markedly increased the growth of clover in the absence of lime and pelleting. On one of these soils (pH 5.4), increasing the inoculation level replaced the requirement for lime or pelleting for maximum plant growth.There were no significant differences between lime and Gafsa-phosphate + dolomite as rcileting materials. 317

Field experiments were undertaken on two infertile and acidic soils in the semi-arid Mackenzie Basin, South Island, New Zealand, to determine the influence of fertiliser placement and rate of N application (0, 15, or row, respectively) but not when N was drilled 20 mm below the seed. Seedling numbers declined in all treatments over summer, and 32 weeks after sowing, numbers were only significantly lower when 30 kg ha -1 N was drilled with the seed (11.1 and 7.9 m -1 , respectively). Early seedling growth of legumes, apart from lupin, responded to N, the largest increases occurring where N was drilled with the seed. Although individual plant weight increases where N was drilled with the seed were still evident 32 weeks after sowing, legume DM yields were not significantly affected because of the lower establishment. Plant growth 32 weeks after sowing was affected by competition from existing vegetation, and increases in individual plant weight and legume DM yield from N occurred only where herbicide was applied. Basal superphosphate was more effective when it was drilled with rather than below the seed. The role of N fertiliser in the establishment of legumes overdrilled into low fertility situations is discussed.

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