Nutrient losses by surface run-off following the application of organic manures to arable land. 1. Nitrogen

• Published in: Environmental pollution (1987) 2001, Vol.112 (1), p.41-51
• Main Authors: Smith, K.A, Jackson, D.R, Pepper, T.J
• Format: Article
• Language: English
• Subjects: Agriculture - methods; Agronomy. Soil science and plant productions; Animals; Applied sciences; Biological and medical sciences; British Isles, England, Herefordshire; Cattle; Cattle slurry; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; England; Eutrophication; Exact sciences and technology; Fresh Water; Fundamental and applied biological sciences. Psychology; Manure; Natural water pollution; Nitrogen; Nitrogen - chemistry; Pollution; Pollution, environment geology; Rainwaters, run off water and others; Soil and water pollution; Soil science; Surface run-off; Surface water quality; Water Pollutants; Water treatment and pollution
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/S0269-7491(00)00097-X

“Capsule”: Run-off nitrogen may increase eutrophication in catchments and affect freshwater biota. Research was conducted on nitrogen (N) surface run-off losses following organic manure applications to land, utilising a purpose-built facility on a sloping site in Herefordshire under arable tillage. Different rates and timing of cattle slurry, farmyard manure and inorganic N and phosphorus (P) fertiliser were compared, over a 4-year period (1993–97). P losses from the same studies are reported in a separate paper. The application of cattle slurries to the silty clay loam soil increased the loss of solids and NH 4 +-N in surface water flow compared to control plots receiving inorganic fertiliser only, or no treatment, but had little effect on NO 3 −-N losses by this route. Results were consistent with other observations that rainfall events immediately after manure applications are particularly likely to be associated with nutrient run-off losses. Losses via subsurface flow (30 cm interflow) were consistently much lower than via surface water movement and were generally unaffected by treatment. Increasing slurry application rate and, in particular, slurry solids loading, increased solids and NH 4 +-N losses via surface run-off. The threshold, above which the risk of losses via surface run-off appeared to be greatly increased, was ca. 2.5–3.0 t/ha slurry solids, which approximates to the 50 m 3/ha limit suggested for slurry within UK ‘good agricultural practice’. Sealing of the soil surface by slurry solids appears to be a possible mechanism by which polluting surface run-off may occur following slurry application on susceptible soils. Total losses of NH 4 +-N and NO 3 −-N during the 4-year monitoring period were insignificant in agronomic terms, but average soluble N concentrations (NH 4 +-N+NO 3 −-N) in run-off, ranging from ca. 2.0 mg/l, up to 14.0 mg/l for the higher rate slurry treatments. Peak concentrations of NH 4 +-N>30 mg/l, are such as to be of concern in sensitive catchments, in terms of the potential for contribution to accelerated eutrophication and adverse effects on freshwater biota.