Nursery establishment technology and seedling production has a key role in rice mechanization development in order to increasing efficiency and improve the performance rice yield in unit area. Technically, suitable and healthy seedling and correct application of transplanting machines are two important steps in mechanical cultivation of rice. Greenhouse experiment was conducted in a factorial randomized complete block design with three replications in Rice Research Institute in Mazandaran, during 2012. A local rice cultivar, Tarom, was used in the experiment. Factors involved in the experiment including different levels of soil pH and soil situation in respect of microbial infection have been set in 5 (4, 5,6,7 and 8) and 2 level (normal and sterlized soil), respectively. Seedlings boxes were irrigated by water with corresponding pH in during the experiment. Sampling of seedling was conducted three times during the growing season and plant height, root length, length of the first leaf, first leaf sheath length, length of the second leaf sheath, length of the second leaf, Length of the third leaf, the third leaf sheath length, leaf area index, crop growth rate (CGR), average leaf area index (LAI) and net assimilatory rate (NAR) were measured. Analysis of variance showed that the effect of pH treatments on plant height, length of the second leaf sheath, third leaf sheath length, dry weight of leaf sheaths, dry weight of seeds, chlorophyll meter readings, crop growth rate (CGR) and net assimilatory rate (NAR) was significant. Soil situation in respect of microbial infection were found statistically significant differences on plant height, sheath length of the third leaf, dry weight of leaf sheaths traits. Comparison of treatment means showed that pH 5 is desirable for the most traits of seedlings Key words: crop growth rate (CGR), net assimilatory rate (NAR), leaf area index (LAI), mechanized cultivation, rice seedlings, soil pH