Indica rice "Takanari" outcompetes japonica rice "Koshihikari" under low fertility conditions in soil developed on a sand dune

Significantly, soil fertility and rice variety influence rice growth. Under different conditions, Indica rice "Takanari (Tak)" outperformed Japonica rice "Koshihikari (Kos)" in terms of N-uptake and biomass production. However, it is still unclear how Tak and Kos respond to rice growth and N-uptake in low-fertility (sandy) and normal (alluvial) soils. Therefore, we conducted a pot experiment at Tsuruoka in the 2022 rice-growing season. Tak and Kos were transplanted individually and interplanted (Tak+Kos) with the main treatments of alluvial soil, sandy, and sand with chemical fertilizers (sand+CF). Rice growth parameters (shoot height, tiller numbers, and leaf color) were weekly investigated, while rice biomass and N-uptake were measured after harvest. Shoot height, rice tillers, leaf color, plant biomass, and N-uptake were significantly different among all treatments. Tak had significantly higher rice biomass and N-uptake than Kos in all treatments for both planting modes. The ratios of aboveground biomass and N-uptake between Tak and Kos in interplanting were higher than their respective ratios in individual planting. The ratios of aboveground biomass in interplanting were higher than in individual planting at 41.7%, 26.4%, and 18.4% in sandy, alluvial, and sand+CF, respectively. Whereas, the ratios of N-uptake in interplanting were higher than in individual planting at 41.9%, 36.6%, and 26.6% in sandy, alluvial, and sand+CF, respectively. Regardless of low growth for both varieties in the sandy, Tak increased the competitive ability of N-uptake and biomass production. Therefore, rice cultivar selection and management of fertilizing practices are required for rice growing in low-soil fertility fields.