Effects of Pig Slurry Treatment with a Peroxide-Based Additive, GasAbate, on the Seasonal Growth of Perennial Ryegrass

Abstract Livestock manures are valuable sources of crop nutrients, however greenhouse gas (GHG) emissions during storage exacerbate climate change and also preclude the closing of nutrient loops. Chemical additives applied during storage can reduce these emissions, where a peroxide-based slurry additive (GasAbate) successfully reduces GHG emissions from stored pig slurry. However, its effects upon crop uptake, and thus plant yields, following land application have not been assessed. To this end, a 5-month pot trial was used to assess ryegrass dry matter (DM) after fertilisation with either untreated (SU) or GasAbate treated (ST) pig slurry post-storage (4 replicates per condition), where an organic topsoil and a heavy gley soil were assessed. Pots were stored under ambient, outdoor conditions and four harvests were performed for DM and grass quality, inferred by measuring chlorophyll content. In both soil types, DM yields across four harvests were consistently higher. In the high OM soil the cumulative yield from ST (122.50 g DM pot⁻ 1 ) exceeded that from SU (101 g DM pot⁻ 1 ) equating to a 21.2% increase ( p < 0.05). In the second, lower OM soil, cumulative yields were lower but again cumulative ST yields (109.0 g DM pot⁻ 1 ) exceeded those from SU (90.6 g DM pot⁻ 1 ) representing a 20.3% increase ( p < 0.05). Chlorophyll indices demonstrated that, in one soil type, ST resulted in grass with higher ( p < 0.05) chlorophyll content which would increase the nutritional value of the pasture. In the two soils tested, GasAbate-treated pig slurry improved ryegrass DM yields, while an increase in chlorophyll content was observed in one soil type. These preliminary findings highlight the additive’s ability to slow the nutrient loss typically seen during slurry storage and potentially improve agricultural circularity.