Photo: Collected
Concerns about water quality in the UK and, in particular, pollution issues in the catchment areas of the rivers Wye and Usk on the England/Wales border have escalated in recent years. Despite the protected status of the rivers, there have been reports of algal blooms, eutrophication, and ecological decline – indicative of an over-abundance of nutrients such as nitrogen and phosphorus.
With the recent surge in a number of poultry farms in the region, the sector has been implicated as a possible contributor. It prompted the British Egg Industry Council to commission ADAS to assess nutrient levels in soils from land that is used for free-range egg production and in watercourses that collect water draining from this land.
Working with egg packers, the BEIC identified “high-risk” free-range egg production farms in the Wye and Usk catchment areas. The risk assessment was based on the location, topography, and history of the operation with ADAS carrying out 17 sampling visits to 14 different farms.
Soil sampling
Soil sampling on the range followed conventional sampling protocols with samples collected in a W-shaped pattern. A minimum of 8 soil samples were collected (approximate depth 7.5cm) on each occasion and these were aggregated into a single composite sample for testing. A control soil sample was also collected from a nearby area of grassland, that was, as far as possible, not grazed by livestock or manure/fertilizer applications. In total, 17 range and 17 control samples were taken.
Water sampling
Suitable locations for water sampling were identified by ADAS, including upstream and downstream samples from a watercourse as close as possible to the point(s) of entry of water from the range land. The timing of the water sample collection was particularly important, as water had to be flowing through ditches and streams adjoining the farm. Periods of drought needed to be avoided as did times when poultry housing orders meant the birds were inside. For these reasons, the sampling period was extended and covered nearly 2 years – July 2021 to June 2023. In total, water data was available from 11 upstream and 11 downstream samples.
Testing
Soil and water samples collected by ADAS were analyzed by NRM Laboratories. For soil, a standard suite of analyses was undertaken, comprising pH, phosphorus, potassium, and magnesium. For water, analyses were for total phosphorus, dissolved phosphorus, total potassium, nitrate nitrogen, and ammonium nitrogen. Biochemical oxygen demand (BOD) and fecal indicator organisms (FIO) were also assessed to provide a guide to organic pollution.
The purpose of the soil analysis was to allow a comparison between range and control land to determine nutrient levels that might be associated with the use of the land by free-range laying hens. Water sampling and analysis were intended to show any changes between upstream and downstream samples, which might be attributable to run-off from the range.
Variations in relative levels of dissolved and total P, nitrate ammonium N, and BOD may also provide a possible indication of the source of the P. High total P and low soluble P, high nitrate and low ammonium N, and low BOD suggest P may be associated with soil input to the water course. High soluble P, ammonium N, and BOD imply that the P may be more likely to originate from organic manures, particularly if associated with high or increased levels of coliform bacteria. See details.
Source: Online/GFMM
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