No description available.

No description available.

In the glasshouse, two cultivars of alfalfa growing in non-sterile soil were evaluated for their response to inoculation with 4 VA mycorrhizal fungi and 3 strains of Rhizobium meliloti. Alfalfa cultivar Hayden PX-1 had significantly greater dry stem weights (p = 0.05) when inoculated with Glomus fasciculatum, G. deserticola or an undescribed Glomus sp. compared to mycorrhizal controls. Alfalfa cultivar Lew HI Nod had significantly less dry stem weights when inoculated with G. fasciculatum, G. mosseae or the undescribed Glomus sp. Addition to R. meliloti did not impart increased growth responses with either alfalfa cultivar probably due to the high nitrogen content of the soil. In the field, alfalfa cultivar Hayden PX-1 was both transplanted and direct-seeded. Transplanted alfalfa had been preinoculated with VA mycorrhizal fungi and R. meliloti. Inocula containing VA mycorrhizal fungi and R.meliloti were Layered below the seed in direct-seeded plots. Phosphorus, as treble super phosphate, was also added as a treatment. At first harvest, transplanted alfalfa inoculated with the undescribed Glomus sp. had significantly greater (p = 0.05) dry whole plot weights compared to controls regardless of R. meliloti or phosphorus treatments. Inoculation of alfalfa with G. deserticola significantly increased dry whole plot weights over controls but significantly (p = 0.05) only with added R. meliloti and phosphorus. Second harvest data maintained the trend for yield increases over controls with addition of the undescribed Glomus sp. and G. deserticola; however, only significantly (p = 0.05) with inoculation with the undescribed Glomus sp. including R. meliloti and phosphorus. Yield increases were not obtained for the final three transplanted alfalfa harvests or for any of the direct-seeded alfalfa harvests. Statistically significant differences in phosphorus and protein content of alfalfa were not found between any of the treatments. Also, differences were not found in soil populations of R. meliloti in mycorrhizal inoculated plots compared to control plots.

No description available.

Attempts at reforestation of many sites in the southwestern United States have repeatedly failed. Experience and research show that moisture stress is the primary cause of seedling mortality. Therefore, it is of utmost importance to produce planting stock for these areas that are as drought tolerant as possible. Seedlings with high ratios of root mass to shoot mass and adequate mycorrhizal infections should be more resistant to harsh conditions than most seedlings currently produced in nurseries and greenhouses. Inferences from other research indicated that the root-shoot ratios of seedlings could be increased solely by decreasing the amount of nitrogen supplied to them. Mycorrhizal formation would also be enhanced by minimal nitrogen levels. Containerized ponderosa pine seedlings (Pinus ponderosa Lawson var. scopulorum Engelm.) were grown in commercial greenhouses at various levels of nitrogen fertilization and treated with several mycorrhizal inoculums. Mycorrhizal treatments significantly increased shoot height and diameter, but no other seedling parameters. The inoculums did not affect the root-shoot ratio or the percent of short roots that became infected. Nitrogen levels significantly affected all parameters measured. As nitrogen concentration increased, shoot height, diameter, and weight increased, while root weight, root-shoot ratios, and mycorrhizal infections decreased. The inverse relationship between fertilizer nitrogen concentration and the resulting root-shoot ratios of the seedlings was linear and highly correlated. Nitrogen and percent mycorrhizal infection was nearly linear and also inversely correlated. The results of this research are immediately applicable to current greenhouse and nursery operations. When stock is to be planted on sites where seedling survival may be compromised by harsh environmental conditions, production methods should be modified to yield seedlings with maximum root-shoot ratios and heavily infected with mycorrhizae.