The uptake of selenium by perennial ryegrass in soils of different organic matter contents receiving sheep excreta

Summary

This experimental study examined how the application of sheep excreta (urine and/or faeces) to soils of contrasting organic matter content affected selenium uptake by perennial ryegrass, a key forage for ruminant livestock. Contrary to expectations, excreta application resulted in either unchanged or reduced selenium concentrations in grass; in high organic matter soils, faeces application significantly decreased selenium accumulation compared to urine, likely through interactions between selenium sorption and microbial reduction. The findings suggest that direct dietary selenium supplementation to animals is more effective for improving ruminant selenium status than relying on manure application to soil.

Regional applicability

These findings are directly applicable to UK pastoral farming, where sheep manure is routinely used as an organic fertiliser and selenium status in grazing livestock remains a nutritional concern. The research suggests that current practice of using ruminant excreta to improve soil fertility may not reliably enhance forage selenium content, with implications for livestock supplementation strategies in organic and conventional UK farming.

Key measures

Selenium concentration in perennial ryegrass tissue (ICP-MS analysis); total selenium accumulation in grass; soil organic matter content; type and source of sheep excreta (urine, faeces, or combination); mineral supplementation type (organic vs. inorganic) in sheep feed; selenium sorption and microbial reduction in amended soils

Outcomes reported

The study measured selenium concentration and total selenium accumulation in perennial ryegrass grown in soils of different organic matter contents after application of sheep urine and/or faeces. Results showed that excreta application either maintained or decreased selenium uptake by grass, with feces significantly reducing total selenium accumulation in high organic matter soil.

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