Optimizing genotype and nitrogen management for improved yield and agronomic efficiency in dry direct seeded rice under temperate ecology

Abstract

Rice production through conventional transplanting is becoming increasingly difficult because of limited water resources and labor shortages. Dry direct-seeded rice (DSR) offers a practical alternative with lower water and labor requirements. However, the success of DSR depends on suitable genotype selection and efficient nitrogen (N) management. Therefore, this study was conducted to assess the influence of genotype, N rate, and split application schedule on yield and agronomic efficiency under temperate conditions. A field experiment was carried out under dry direct-seeded conditions using three temperate rice genotypes: Shalimar Rice-3 (SR-3), Shalimar Rice-4 (SR-4), and SKAU-484 (SK-484). Three nitrogen rates (0, 120, and 150 kg N ha⁻¹) were tested in combination with three split-application schedules (3, 4, and 5 splits). Data were recorded on crop phenology, grain and protein yield, thermal indices, and nitrogen-use efficiency. Significant differences were observed among genotypes and nitrogen treatments. SR-3 produced the highest grain yield (6.4 t ha⁻¹), which was 14% higher than SR-4 and 5% higher than SK-484. Grain and protein yields increased with N application. Application of 120 kg N ha⁻¹ produced near-maximum grain yield (6.7–7.4 t ha⁻¹) compared with 150 kg N ha⁻¹ (6.9–7.6 t ha⁻¹), although grain yield was significantly higher under N150 in 2025. The highest grain yield (7.3 t ha⁻¹) was recorded with 120 kg N ha⁻¹ applied in five splits, which was slightly higher than 150 kg N ha⁻¹ applied in three splits (7.1 t ha⁻¹). SR-3 also required fewer heat units to reach maturity and showed higher heat use efficiency, hydrothermal unit efficiency, and agronomic N-use efficiency. In contrast, the zero-N treatment markedly reduced these efficiency indices. The highest agronomic N-use efficiency was obtained with 120 kg N ha⁻¹ (16.7–17.2 kg kg⁻¹), representing an approximately 15% improvement over 150 kg N ha⁻¹. The results indicate that SR-3, 120 kg N ha⁻¹, and increased N splitting were associated with improved grain yield and nitrogen-use efficiency. Thus, cultivation of SR-3 with an appropriate N rate and split application strategy may be considered a promising option for enhancing the productivity and sustainability of dry direct-seeded rice under temperate northern Indian conditions.