SummaryThe effects of temperature on growth in broth and soil and on competition for nodule formation between Rhizobium japonicum serotypes USDA 76 and 94 compared to 6 and 110 were studied. Increasing root temperatures of Lee soybean from 20 to 35~ increased the competitiveness of 76 and 94 relative to 6 and 110 for all inoculum ratios such that at 30 and 35~ symptoms of Rhizobium-induced chlorosis appeared. Tolerance to elevated temperatures was exhibited by 76 and 110, but not 94 and 6 in broth and soil which suggested that increased competitiveness of 76 and 94 at high soil temperatures was not dependent upon growth at elevated temperatures. Nodulation and vegetative growth of Lee soybeans were at a minimum at 20~ and optimum at 30~ Differences in competitiveness of 6 to previous studies indicated the need to standardize temperatures of assays. Differences in growth responses of 76 and 94 to temperature from a previous study suggested a confounding effect on different carbon sources in growth media.
Developmental and functional responses of the tripartite bean symbiosis were demonstrated to be indicators of allelopathy potential of a cabbage intercrop. A field experimental approach using a modified Nelder Fan design tested 3 intercrop proportions at 7 planting distances for a range of allelopathic interactions. Greater cabbage proportion generally reduced VAM infection and bean biomass, N and P but increased nodulation, except at the lowest planting distances. In addition, an intermediate proportion treatment at the higher distances produced positive effects of bean biomass, N and P which represented a potential over-yielding mechanism. The allelopathic basis for only the negative effects was corroborated in the greenhouse with plants grown in Leonard jars but not in a recirculating root exudate apparatus. (1,2). These crop-crop interactions will have a significant impact on the practice of intercropping which is "a cultural practice in which two or more crops and/or wild plants are grown in the same field with both temporal and spatial overlap" (3). Numerous crops have now been identified as having an allelopathic potential, e.g. oats, sunflower, alfalfa, celery, etc. (1,4,5), and their use as intercrops would promote greater occurrences of allelopathic interactions. This chapter presents the background and experimental approaches for evaluating the role of brassica crop-based allelopathy when intercropped with leguminous crops. While the studies of allelopathy in agroecosystems have focused on crop-weed interactions, there have also been demonstrated crop-crop interactions, such as with rotations of monocultures Allelopathy and IntercroppingThe study of crop-based allelopathy is essential to ensuring successful intercropping because of its potential to impact important over-yielding factors of 0097-6156/95/0582-0193$08.00/0
Abstract. Although phosphate mining necessarily destroys extensive amounts of wildlife habitat, the industry attempts to minimize the long-term effects of the strip mining by reclaiming some of the land to make it suitable for wildlife. We have studied a spectrum ofunmined (reference) and previously mined (reclaimed) lands to determine how well reclaimed lands can support vertebrate wildlife species. We studied 100 sites, spread over an area of about 1,000 square miles of west-central Florida. Thirty reference sites were xeric (dry) uplands (scrub, sandhill), and 30 were mesic (moderately wet) flatlands (pine flatwoods and dry prairies), and the remaining 40 were reclaimed sites that varied from mesic-like to xericlike in their flora and fauna. Mesic flatlands are more extensive than the xeric uplands which often are patchy habitat islands surrounded by mesic flatlands. Collectively, xeric upland and mesic flatlands each support about 75 resident vertebrate species. Individually, mesic sites supported fewer species than mesic sites. Reclaimed sites, whether mesic-like or xeric-like, supported fewer species than respective reference sites. We documented a 50% overlap of resident species at mesic and xeric reference sites. "Focal species" are those that are under-represented at reclaimed sites relative to reference sites. The total list of focal species, from the xeric (28 species) and mesic (12 species) sites combined, includes 5 amphibians, 8 reptiles, 1 mammal, and 17 birds. Roughly 60% of the focal species resided at xeric reference sites, 10% resided at mesic reference sites, and 30 % were resident of both reference sites. Our fmdings indicate that current reclamation practices are not adequate to maintain a vertebrate fauna representative of the regional mesic flatlands and xeric uplands. All of our results indicate that the reclamation of terrestrial habitats for wildlife in central Florida should be planned on a broad scale and integrated to include the mostly protected hydric habitats, the relatively extensive mesic habitats, and the patchy xeric habitats. Additional
A field experiment was conducted to evaluate the effect of Rhizobium inoculation methods and the effect of different levels of N fertilization on nodulation, nitrogen fixation and yield of Phaseolus vulgaris L. The N treatment produced a seed yield significantly higher than that of the other treatments. Inoculation treatments had no significant effect on nodule number and dry weight, even when compared to the noninoculated and N controls. This finding was attributed to a high number of Rhizobium phaseoli in the soil. The applications of N and inoculation did not significantly affect the N percentages of foliage and grain or nitrogenase activity. Serological identification of nodules indicated that the native strain UPRM 6000 farmed the largest percentage of nodules (41%), followed by R. phaseoli 127K44 (34%), 127K17 (13%) and 127K12b (10%). The serogroup distributions of inoculated and N fertilized treatments differed significantly from the noninoculated control. Inoculation methods (seed vs. soil) did not differ significantly in either nodulation or yield responses.
The combined effect of N fertilization and Rhizobium inoculation on bean (Phaseolus vulgaris L., cv. Bonita) nodulation and yield was studied in the semi-arid southern region of Puerto Rico. Six N treatments: 0, 22, 45, 90, 180 and 360 kg/ha were tested in inoculated and noninoculated plots arranged in a split-plot design with 4 replications. The application of 22 kg/ha of N in the inoculated plots increased plant nodulation 4 and 8 weeks after planting. Higher rates of N fertilization reduced the number and size of bean nodules at both sampling dates. On the other hand, dry beans consistently increased with applications of 0 to 180 kg/ha of N in the presence of Rhizobium.
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