K.A. Smith

Ammonia emission factors for UK agriculture

Ammonia (NH3) emission inventories are required for modelling atmospheric NH3 transport and estimating downwind deposition. A recent inventory for UK agriculture, estimating emission as 197 kt NH3–N yr−1, was constructed using 1993 statistical and census data for the UK. This paper describes the derivation of the UK-based emission factors used in the calculation of that emission for a range of livestock classes, farm practices and fertiliser applications to agricultural land. Some emission factors have been updated where more recent information has become available. Some of the largest emission factors derived for each farming practice include 16.9 g NH3–N dairy cow−1 d−1 for grazing, 148.8 g NH3–N liveweight unit−1 yr−1 for housed broilers and 4.8 g NH3–N m−2 d−1 for storage of solid pig and poultry waste as manure heaps. Emissions for land spreading of all livestock waste were 59% of the total ammoniacal nitrogen (TAN) applied as a high dry matter content slurry and 76% of TAN applied as farm yard manure. An updated estimate of emission from UK agriculture, using updated emission factors together with 1997 statistical and census data, is presented, giving a total of 226 kt NH3–N per year.

Nutrient composition of poultry manures in England and Wales

Abstract In this study, 121 poultry manure samples were collected from commercial holdings in England and Wales. The nutrient contents of the individual manure samples varied widely. In general, broiler/turkey litters had a higher dry matter content (c.60%) than layer manures (c.35%), although all manure types had similar concentrations of nutrients (N, P, K, Mg, S) on a dry weight basis. Typically N:P:K ratios were 6:2:2 for layer manures and 6:2:3 for broiler/turkey litters. The readily plant available N content (ammonium-N+uric acid-N) of the poultry manures was 30–50% of the total N. The dry matter content of poultry manures is suggested as a useful indicator of total fresh weight nutrient concentrations.

Spring applied organic manures as a source of nitrogen for cereal crops: experiments using field scale equipment

The effects of spring top-dressed applications of broiler litter, pig slurry and cattle slurry on winter wheat and winter barley yield and quality were investigated on a field scale at three UK sites between 1992 and 1994, using commercially available application equipment. Broiler litter was applied at rates ranging from 5.3 to 8.8 t/ha, and slurries from 54 to 89 m 3 /ha. Few practical problems were encountered when spreading broiler litter, but when spreading cattle slurry there was some crop damage and soil compaction from the tanker wheelings adjacent to tramlines. Coefficients of variation for manure spreading using commercial spreaders ranged from 20 to 32%. Spring applied manures increased yields of winter wheat and winter barley, and lowered optimum inorganic fertilizer nitrogen (N) rates. When the N efficiency of the manures was compared to that of inorganic fertilizer N, broiler litter N efficiencies ranged from 10 to 49 %, cattle slurry was c. 30% and pig slurry c. 50%. The experiments demonstrated that poultry litters and slurries can be applied successfully to growing cereal crops in spring as part of an integrated policy for N supply.

Crusting of Stored Dairy Slurry to Abate Ammonia Emissions

Storage of cattle slurry is a significant source of ammonia (NH3) emissions. Emissions can be reduced by covering slurry stores, but this can incur significant costs, as well as practical and technical difficulties. In this pilot-scale study, slurry was stored in small tanks (500 L) and the effectiveness of natural crust development for reducing NH3 emissions was assessed in a series of experiments. Also, factors important in crust development were investigated. Measurements were made of crust thickness and specially adapted tank lids were used to measure NH3 emissions. Slurry dry matter (DM) content was the most important factor influencing crust formation, with no crust formation on slurries with a DM content of <1%. Generally, crusts began to form within the first 10 to 20 d of storage, at which time NH3 emission rates would decrease. The formation of a natural crust reduced NH3 emissions by approximately 50%. The type of bedding used in the free stall barn did not influence crust formation, nor did ambient temperature or air-flow rate across the slurry surface. There was a large difference in crust formation between slurries from cattle fed a corn (Zea mays L.) silage-based diet and those fed a grass silage-based diet, although dietary differences were confounded with bedding differences. The inclusion of a corn starch and glucose additive promoted crust formation and reduced NH3 emission. The maintenance of a manageable crust on cattle slurry stores is recommended as a cost-effective means of abating NH3 emissions from this phase of slurry management.

Behaviour and Impact of Cow Slurry Beneath a Storage Lagoon: 1. Groundwater Contamination 1975–1982

The chemical and biological composition of groundwater sampled from a 76 m deep borehole situated 80 m from an unlined, earth-banked lagoon excavated in Upper Chalk and continuously used to store liquid cow manure was regularly monitored from August 1975 to January 1982 for signs of pollution. The lagoon became self-sealing 3 months after the start of filling in 1975, but was further enlarged and re-filled in autumn 1976, and emptied by dragline in September 1978 and 1980. No significant changes in groundwater composition were detected in the period August 1975 to December 1978. In January 1979, significant numbers of Escherichia coli and a large, rapid increase in concentrations of ammonium-nitrogen (NH4-N), phosphorus (P), potassium (K), sodium (Na), chloride (Cl) and sulphate (SO4) were detected in the groundwater. Nutrient concentrations fluctuated at elevated levels throughout 1979 but decreased during 1980. Additional bacterial and chemical (NH4-N, P and K) contamination was recorded in January 1981 and subsequent months. The contamination was considered to have occurred as a result of fissure flow through the unsaturated zone of the Upper Chalk following repeated disruption of the self-sealing layer during emptying of the lagoon by dragline in September 1978 and 1980. The results indicate that unlined, earth-banked slurry storage lagoons need to be carefully managed to avoid biological and chemical pollution of Chalk aquifers.

Effects of slurry application method and timing on grass silage quality

Small-scale silos (60-litre polyethylene barrels) were used to examine the chemical composition of grass silage after the application of slurry, at 40 m 3 /ha, at a range of timings, at two sites with contrasting rainfall; North Wyke, in Devon (high rainfall) and Reaseheath College, Cheshire (low rainfall). Grass plots (60 m 2 ) received cattle slurry via surface broadcast (S), shallow injection (I) or surface placement by trailing shoe (T) techniques at 10, 6 or 2 weeks before an early silage (first) cut in May/June, and 6 or 2 weeks before a second cut in June/July. Control plots (C) received no slurry treatment. The harvested grass was compressed and sealed in the experimental silos and samples of the herbage at ensiling and of ensilage (after >100-day fermentation) were analysed for various chemical components. Herbage yield was measured when the harvests were taken. Wetter than average weather conditions in both years resulted in silages with variable DM content (range 140–277 g/kg) being made at both sites. Generally, silages were poorly preserved with high pH and NH 4 + -N and low lactic acid contents. In particular, the silages from treatment S where slurry was applied 2 weeks prior to harvest exhibited characteristics indicative of clostridial growth, with high pH (range 4·0–5·2) and NH 4 + -N (106–213 g/kg total N) and low lactic acid (16–86 g/kg DM) contents. Damage to herbage caused by the injection tines on taller swards (treatments I at 6 and 2 weeks before cutting) was evident and the injection process was impeded by tall grass. This contributed to herbage contamination with soil and slurry on these treatments and, consequently, to poor silage fermentation. Silages made with slurry application method T at all timings showed improved fermentation characteristics compared with the other treatments, particularly at North Wyke. The results indicate that silage quality is unlikely to be compromised by slurry applications made in early spring, during February, March or even in April, where these are at agronomically sensible rates. Such practice will enable better utilization of slurry nitrogen (N), reducing risks of nutrient losses via leaching or surface runoff. Furthermore, shallow injection and, particularly, trailing shoe slurry application techniques may be used to increase flexibility of slurry management by allowing more immediate spreading before cutting than with conventional surface broadcasting, without detriment to silage quality.

Nitrate Leaching from Livestock Manures in England and the Implications for Organic Farming of Nitrate Control Policy

ABSTRACT European Community legislation will require controls upon agriculture to reduce nitrate leaching. A voluntary pilot Nitrate Sensitive Area (NSA) Scheme to assess the impact of changed husbandry practices on nitrate leaching has been in operation in England for three years. It is proposed to expand it in 1994 under the EC Agri-Environment Regulation. Research findings have shown that livestock manures applied in autumn and early winter increase nitrate leaching from both arable and grassland. Cover crops reduce the loss of nitrate. The initial loss from straw- based manures is less than from slurries and poultry manure. The original proposals for the future NS As included limits on the use of all manures which could have prevented organic farms from participating in such schemes. These plans have been modified in a way which will allow many organic systems to join the Scheme but not outdoor pig or poultry units. Organic farmers hope that when Vulnerable Zones are delineated under the EC Nitrates D...

Impact of hydrology and effluent quality on the management of woodchip pads for overwintering cattle. I. Development of monitoring methodology and sampling strategies

(Received27June2011;revised24November2011;accepted16March2012;firstpublishedonline12April2012)SUMMARYWoodchip pads can be a sustainable alternative to the overwintering of stock on grassland or in conventionalhousing and can offer benefits in improved animal performance, improved health and environmentallysustainable options for the management of animal excreta (dung, urine and the resulting effluent). Novel flowmeasuring equipment was developed to monitor effluent drainage from twowoodchip pads sited on commercialfarmsintheUK,oneinPowys(Wales,UK)andtheotherinLeicestershire(England,UK).Observationsweremadeover 8 months in 2009/10. The aim was to assess both hydrological characteristics and nutrient fluxes. Flowmonitoring, based on the use of tipping bucket or the principles of an overshot water wheel, was required to becapable of diverting a sample into a storage tank for sub-sampling and subsequent analysis. Estimates of padoutputs through evaporation and sub-surface drainage accounted for 0·98–1·01 of total inputs from precipitationand animal excreta, with evaporation and pad drainage representing 0·47–0·63 and 0·34–0·51 of total inputs,respectively. The resulting scientific information is of value in the synthesis of guidelines for design, constructionand management of woodchip pads. Detailed analysis of flow and precipitation data, coupled with columnabsorptionstudiestoevaluatemoistureretentioninthewoodchipmatrix,wereusedtoconsiderthe developmentof modelling approaches, with the potential to predict drainage outputs across a range of geographical, weatherand pad management situations.INTRODUCTIONThereiscontinuedinterestintheuseofwoodchippads(P.FrenchM CREH 2005; Vinten et al. 2006).