Franseria dumosa Gray and Hilaria rigida (Thurb.) Benth. ex Scribn. seedlings were grown in a glasshouse in potted soil which was collected from the Mojave Desert near Mercury, Nevada. The soil represented areas under living shrubs and also areas between shrubs. Soil was either steam sterilized or not steam sterilized. The sterilization resulted in greatly decreased yields of plants possibly because of induced P deficiency. It was suggested that symbiotic mycorrhizae necessary for P absorption for the species involved might have been eliminated by the sterilization. The effect did not hold for a noncalcareous soil well supplied with available P. Soil sterilization increased both Mn and Zn in plants. There was an interaction in that plants did not grow well in soil from under shrubs regardless of steaming indicating possible allelopathic effects.
Introductio~ยข
Other studies in this laboratory had indicated that Frctnseria dumosa Gray seedlings grew poorly in the glasshouse in soil obtained from the Northern Mojave Desert where this species grows naturally. The purpose of this experiment was to determine if the poor growth could be related to steam sterilization of soil.
Materials c~nd methods
Soil was obtained from near Mercury, Nevada in the Northern Mojave Desert. Soil from under shrubs constituted one test lot and soil from between shrub clumps constituted another. Soil characteristics will be given in a separate report s. The soils were highly calcareous and of pH about 8.5. The soil for half the plants was sterilized in a steam autoclave. F. dumosa seedlings or Hilaria rigida (Thurb.) Benth. ex Scribn. seedlings were planted into 2000-g quantities of each kind of soil in a glasshouse with six replicates. Soil moisture was kept near one-third bar by use of distilled-deionized water. After 90 days the plants were harvested, shoots were washed in distilleddeionized water, dried, weighed, and ground for analysis by emission spec~rography. There were six replications.
F. dumosa seedlings were also grown with and without steam sterilization in 1000-g quantities of Yolo loam (noncalcareous pH 6) and Hacienda loam