Assessment of Phosphorus Supply Rate to Common Vetch By Using Ion Exchange Membranes

Abstract

In the present study we examined the suitability of resin membranes (Plant Root Simulator^TM, PRS) to estimate phosphorus (P) supply rate. For this purpose common vetch (Vicia sativa L.) was gown in a pot experiment with no P fertilization (P₀ = 0 kg P / ha) and with P fertilization (P₁ = 87 kg P / ha), and P supply rate was assessed using a specially pretreated anion exchange membrane encased in a plastic applicator buried in the soil for 2-week intervals. Cumulative P supply rate was also calculated at the end of the growing season. Soil moisture content was kept at field capacity and soil temperature was recorded daily throughout the growing season. Results showed that resin membranes assessed considerably greater soil P supply rate in the treatments including P fertilization compared to the control either in pots planted with common vetch or in bare soil. Without root competition (unplanted pots) soil P supply rate ranged on average from 3.89 μg ion /10 cm² / 2 weeks (P₀) to 59.28 μg ion / 10 cm² / 2 weeks (P₁). When root completion was considered (pots planted with common vetch) P supply rate varied on average from 2.70 μg ion / 10 cm² / 2 week (P₀) to 44.91 μg ion / 10 cm² / 2 week (P₁). Under the same P treatment, soil ion movement processes (i.e., ion diffusion) that can be modified by the presence of root hairs may explain the small differences in absolute values between planted and unplanted pots. The cumulative value of P supply rate was significantly lower in the treatment with common vetch plants and fertilizer addition than under bare soil and the same amount of fertilizer. Yield-related parameters and P concentration in aboveground plant parts were comparable to those referred in the literature. The P supply rate was more closely related to P uptake by plants (r² = 0.96), which is considered strong evidence that this method of availability estimation is effective and may be used for this purpose. The PRS probes under controlled soil conditions with respect to temperature and moisture may estimate P supply rates to common vetch plants successfully. They seem to be capable of differentiating P supply in fertilized soils and give results significantly correlated to yield parameters of this crop. However, it is not recommended to use them for making fertilizer recommendations before they are tested under natural conditions, especially in dry environments.

Keywords:

• Anion exchange membranes
• soil–plant phosphorus
• Vicia sativa L.
• yielding parameters

Acknowledgments

We acknowledge the technical assistance provided by the personnel of the laboratory of the Institute of Soil Mapping and Classification and we especially thank Gripari Paraskevi for performing the laboratory analyses. Special appreciation goes to Rigas Karamanos for providing the PRS technology to our institute.