Rice nitrogen uptake as affected by different nitrogen application depths

ABSTRACT

Subsoil nitrogen (N) can contribute to rice (Oryza sativa L.) nutrition and affect its response to N fertilization. The N recovery by depth for flooded rice using ¹⁵N was evaluated in three undisturbed soils (varying in their physical and chemical properties) in a greenhouse experiment. Rice was grown after ¹⁵N-labeled ammonium sulfate application at the soil surface and at 0.10, 0.20, 0.30, and 0.45 m depths. The N located at greater depths was absorbed over time, resulting in a similar ¹⁵N concentration in leaves among treatments at rice heading. The N-fertilizer application at the near soil surface resulted in higher dry matter production for all soils, with a constant decrease with depth. Although, ¹⁵N recovery and N derived from fertilizer were greater with N application at 0.10, 0.20, or 0.30 m depth, probably due to N dilution effect caused by soil N and greater N loss at the soil surface. The intensity of ¹⁵N recovery from 0.45 m was related to soil properties, such as hydraulic conductivity. Even later in the season, rice plants effectively used N from subsoil layers, therefore greater soil depths should be considered in studies regarding correlation and calibration of soil-based N tests for N-fertilizer recommendations.

KEYWORDS:

• ¹⁵N uptake
• N derived from fertilizer
• fertilizer use efficiency
• paddy soil
• Oryza sativa L

Acknowledgements

The authors gratefully acknowledge all students and staff for their contributions in the development of this research.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was financed (grant and scholarships) in part by the Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and the Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - Brasil (CAPES) [Finance Code 001].