Integrating soil phosphorus sorption capacity with agronomic indices to improve sustainable P use in agriculture
Sifan Yang, Blánaid White, Fiona Regan, Nigel Kent, Rebecca L. Hall, Karen Daly
Journal of Soils and Sediments
School of Mechanical and Manufacturing Engineering
Journal of Soils and Sediments
Abstract

Purpose

Phosphorus (P) sorption processes in soils can influence P plant-availability and influence ‘build-up’ and ‘draw-down’ P cycles. Current fertiliser recommendations do not take these processes into account. This study aimed to integrate soil P sorption behaviour and P agronomic-indices to strengthen P management recommendations.

Methods

Mineral soil covering 35,716-km2 of Ireland was characterised by P status (Morgan’s P and Mehlich-3 P), and Langmuir sorption parameters of P sorption maximum capacity (Smax, mg·kg−1) and binding energy (k, L·mg−1).

Results

Segmented regression between Smax and M3-Al (R2 = 0.49) identified a significant change-point at Smax = 450.03 mg·kg−1, at which soils can be placed into ‘low’ (SLM3-Al) and ‘high’ (SHM3-Al) P sorbing classes. Sorption parameters in SLM3-Al did not change with soil P status; however, in high P sorbing soils, sorption parameters significantly correlated with P status. High sorbing soils that are P-deficient (Index 1 and 2) will ‘fix’ P and take longer to build-up plant available P to a value for agronomic production (Index 3). Low P sorbing soils at high P status (Index 4) will decline to Index 3 at faster rates than high P sorbing soils. These soils (SLM3-Al) are at higher risk of soluble P losses to water because of lower binding energies.

Conclusions

Efficient P fertiliser use can be more effective if soils are delineated into ‘low’ and ‘high’ sorbing soils coupled with soil P status. By integrating P sorption capacities with agronomic soil P indices, fertiliser advice and water quality measures can be targeted and more effective.