Biomass, nodulation and N₂ fixing response by subclover and pink serradela to phosphorus fertilization

ABSTRACT

In Mediterranean areas, sustainable production of rainfed pastures is associated with plant species which withstand low soil fertility and variable annual drought, phosphorus (P) being the primary limiting nutrient for legume growth and N₂ fixation. A study was undertaken under environmentally controlled conditions to compare the response of subclover and pink serradela to P supply using a moderately acid soil, very poor in available P, in terms of biomass, nodulation pattern, N₂ fixation and P use efficiency. A P dose in the range of 30–60 kg P ha⁻¹ is recommended as a starter for pastures under the present conditions. A higher P rate reduced the fixing nodule number and biomass, and the N₂ fixation rate. Fixed N₂ per unit of nodule P by pink serradela as monocrop was about 80% greater than the sole subclover, demonstrating its higher efficiency on the use of nodule P. Thus, pink serradela needs a lower P rate to produce the same amount of biomass per unit area as sole subclover. Long-term studies in field conditions, using these and other new pasture legume species are needed to consolidate the present findings.

KEYWORDS:

• Mediterranean condition
• N₂ fixation
• ¹⁵N technique
• pasture legumes
• phosphorus (P) partitioning in plant organs

Acknowledgments

Authors acknowledge the enterprises Fertiprado for providing seeds and Interface for assisting the distilling water used for irrigation. Acknowledgements are also due to the Laboratorio de Isótopos Estables (Universidad Autónoma de Madrid) for ¹⁵N analysis, and the Soil Laboratory (ISA/UL, Portugal) for other soil and plant analyses.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This research was supported by the PEst-OE/AGR/UI4129/2015-2018 project funded by the Foundation for Science and Technology.