Effect of seed rate and row spacing on the performance of early and late maturing rice cultivars in mixed crop systems under intermediate deepwater conditions (15–50 cm)

Summary

A field experiment was conducted in 1990 and 1991 under intermediate deepwater conditions (15–50 cm) at Cuttack, India with two rice cultivars - Banaprabha, a semi-tall (130 cm), short duration (95 days), upland cultivar and Gayatri, a photosensitive, semi-dwarf (100 cm), lowland cultivar of long duration (170 days). The cultivars were direct-sown either in pure stands using 400 seeds/m² at 20 cm row spacing or in mixed stands composed of alternate rows sown with 200, 300 or 400 seeds/m² each at 10, 15 or 20 cm inter-row spacing. Mixed-row cropping of Banaprabha and Gayatri produced 17–21% higher grain yield than a pure crop of Gayatri. Panicles/m² increased with higher seed rate and decreased with wider row spacing but a reverse trend was observed in panicle weight. Maximum grain yield was obtained at a row spacing of 15 cm but the effect of varying seed rates at each row spacing was non-significant. Gayatri produced up to 82% of its pure crop yield and contributed up to 70% of the total yield in the mixed crop system. Therefore, the yield advantage under mixed cropping was due to the late maturing cultivar benefitting from the increased area available after the harvest of the early cultivar. A crop stand using 200–300 seeds/m² of each cultivar at a 15 cm row spacing was found to achieve the optimum productivity from the mixed cropping system.