Response of wheat to phosphorus-enriched ironstone gravel

Authors

David Weaver, Department of Primary Industries and Regional Development, Western AustraliaFollow
David Rogers, Department of Primary Industries and Regional Development, Western AustraliaFollow
Ron Master, Department of Primary Industries and Regional Development, Western AustraliaFollow
Peta Richards, Department of Primary Industries and Regional Development, Western AustraliaFollow
Robert Summers, Department of Primary Industries and Regional Development, Western AustraliaFollow
Simon D V Clarendon, Department of Primary Industries and Regional Development, Western AustraliaFollow

Document Type

Article

Publication Date

7-1-2025

Journal Title

Soil Research

ISSN

ISSN: 1838-675X, eISSN: 1838-6768

Keywords

adsorption, desorption, ironstone gravel, phosphorus, responsiveness, volumetric water content, wheat, yield

Disciplines

Agricultural Science | Agronomy and Crop Sciences | Soil Science

Abstract

Context

Gravel fractions ( > 2 mm) in soil are almost always excluded from laboratory analysis and glasshouse experiments as they are considered to be inert; however, the > 2 mm fraction is always present in field experiments. Aims

To determine whether the > 2 mm fraction of ironstone gravel (IG) soil enriched with phosphorus (P) can supply P to wheat (Triticum aestivum L.). Methods

An IG soil was separated into different size fractions ( < 2, 2–4, 4–6, 6–8 and 8–10 mm), and adsorption and desorption experiments, volumetric moisture measurements and glasshouse experiments were conducted. Each of the > 2 mm fractions were enriched with P to different levels and added to a sand culture, or to the enriched < 2 mm fraction in different amounts (25%, 50% and 75% IG). Wheat was grown in pots and growth correlated to P added from enriched soil fractions, weighted Colwell P, soil solution P concentrations and volumetric water content. Key results

The < 2 mm fraction of the IG soil adsorbed more P than the > 2 mm fraction of the IG soil likely due to its greater specific surface area. Volumetric water content decreased as gravel amount increased. Wheat was more responsive to P for larger compared to smaller gravel sizes. The P-enriched IG was able to support the growth of wheat in the absence of any other P source. For the same level of P enrichment, dry matter decreased as gravel amount increased. Conclusions

The IG influences wheat growth through P retention and release and soil moisture. Volumetric water content can be reduced significantly by high gravel contents, leading to reduced wheat growth despite sufficient P fertility. Implications

Depending on the nature of the soil matrix, soils with high amounts (~50%) of larger IG are likely to require lower P applications to optimise crop yield. Soil sampling strategies and laboratory testing need to consider how to practically include the > 2 mm fraction during sample collection and analysis.

Recommended Citation

Weaver David, Rogers David, Master Ronald, Richards Peta, Summers Robert, Clarendon Simon (2025) Response of wheat to phosphorus-enriched ironstone gravel. Soil Research 63, SR24151. https://doi.org/10.1071/SR24151