Abstract

In order to investigate the effects of plant density and the role silicon plays in determining the agronomic features of rice transplanted as single plants and planted in hills, an experiment in the split factorial design in the format of randomized complete block design with three replications was conducted in Sari in 2007. The main factor consisted of two levels of silica (applying and not applying it), and the subordinate factor included two modes of planting rice (in hills and as individual plants) and three plant densities (40, 80, and 120 plants/m²). Results obtained showed that applying silica improved some agronomic features. For example, the total number of tillers per plant increased by 11.6%, the number of effective tillers per plant by 14.2%, and the seed yield by 18.2%; and, therefore, the harvest index, compared to the control (in which silica was not applied), increased by 4.4%; but the percentage of filled spikelets decreased by 13.9% (which was a significant reduction). Increasing plant density from 40 to 120 plants per m² caused deterioration in some agronomic features. For example, plant height, the total number of tillers, the number of effective tillers per plant, and the total number of spikelets per panicle decreased by 5.04, 51.94, 55.1, and 20.44%, respectively. The mode of planting had a significant effect only on the total number of effective tillers per plant, and on the total number of spikelets per panicle, at the one percent probability level; and it also significantly influenced the percentage of filled spikelets at the five percent probability level. Under the interactive effects of the three variables, the maximum seed yield was obtained in the treatment of applying silica and planting density of 80 plants per m² in transplanting rice as single plants and in hill planting (424.1 and 414.6 g/m^-2, respectively).

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