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This study evaluated 48 rice genotypes under different nitrogen forms (ammonium versus nitrate) and water conditions (irrigated versus rainfed) across two seasons. Ammonium nutrition produced higher grain yields than nitrate, with advantages of 26.2 g/m² under irrigation and 154.2 g/m² under rainfed conditions, though responses varied by genotype. The research combined agronomic measurements with biochemical enzyme activities and gene expression analysis to show that nitrogen form preferences are genotype- and environment-dependent.
Why it matters
With increasing adoption of direct-seeded rice due to water and labor constraints, understanding how different rice varieties respond to nitrogen sources under varying water availability can improve fertilizer management strategies. The findings suggest that ammonium-based fertilization may be particularly beneficial for rice production in water-limited rainfed systems, potentially improving nitrogen use efficiency and yield stability.
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⚠️ Preprint – Noch nicht peer-reviewed
Dieser Artikel wurde noch nicht von unabhängigen Experten begutachtet. Die Ergebnisse sind vorläufig und sollten mit Vorsicht interpretiert werden.
Considering the increasing water and labor constraints in rice production, direct-seeded rice is becoming increasingly important. However, direct-seeded rice is vulnerable to water stress and inefficient nutrient use. Nitrogen use efficiency in rice is generally low, and improving nitrogen acquisition and assimilation is important for sustainable productivity. In this study, 48 recombinant inbred lines were evaluated under ammonium and nitrate nutrition in irrigated and rainfed environments across two cropping seasons. Agronomic, physiological, biochemical and molecular responses were assessed. Significant effects of genotype, nitrogen form, environments and their interactions were observed for several traits. Rainfed conditions reduced grain and biological yield compared with irrigated conditions. Ammonium produced a higher mean grain yield than nitrate by approximately 26.2 g m-2 under irrigated conditions and 154.2 g m-2 under rainfed conditions, although the responses varied among genotypes. Biological yield and SPAD values were generally higher with ammonium, whereas total chlorophyll showed season and environment-dependent responses. Glutamine synthetase activity was highest under ammonium treatment, while glutamate synthase activity was higher under nitrate treatment. Grain yield showed strong positive correlations with biological yield, but correlations between grain yield and GS or GOGAT activity were not significant. Expression of OsGln1.2, OsGln2 and OsGlt1 varied according to genotype, tissue and nitrogen treatment. Overall, the results demonstrate that responses to nitrogen forms are genotype- and environment-dependent, and that ammonium may provide a yield advantage under rainfed conditions. Integrating field performance with biochemical and molecular traits may help identify rice genotypes suited to water-limited systems.