Nitrogen and phosphorus availability to ryegrass in an acidic and limed zeolite-amended soil

Nitrogen and P fertilization increases crop yields, especially in acidic soils, but its effect may be minimized by various N loss and P retention processes. Zeolite may enhance N and P fertilizer efficiency. The aim of this study was to compare N and P availability and recovery efficiencies to ryegrass, as well as soil available nitrogen, in acidic and limed zeolite-added soils. In a pot experiment with ryegrass we added escalating zeolite quantities to an acidic and limed soil and we measured soil NH4-N dynamics and N and P in plant. Added zeolite protected NH4-N by releasing it more slowly when compared to the no-zeolite treatments. Recovery efficiency (uptake compared to added nutrient) increased with zeolite from 11.7% (no-zeolite) to 30% (zeolite treatment) for N and from 1.52% to 4.02% for P. Even under the unfavourable conditions of an acidic soil, N and P recovery efficiencies were greatly improved due to zeolite. This was induced by the slow release of ammonium cations, which kept the available NH4-N unchanged and due to the protection of the available P from being retained onto soil colloids