Outwintering on sacrifice areas
This study has shown that outwintering of beef and dairy cows can lead to significant levels of water body pollution by ammonium, phosphorus and other particulate contaminants. Such pollution arises due to rapid transport of components of deposited excreta to tile drains through macropores in saturated soil during or after rainfall. Saturated soil conditions arise around the periphery of any field areas which have become compacted due to trampling by animal hooves, and this situation is almost inevitable during outwintering.
Saturated soil can also arise in a second situation after prolonged rainfall if the tile drainage system is inadequate so in effect the water table rises to the surface. In this situation, there is a significant additional level of pollution further to that arising from soil compaction due to trampling. It is very obvious when this second situation arises as it is associated with surface runoff and ponding.
Sacrificing an area requires planning and management to minimise the environmental damage from outwintering cattle. Increasing pressures on costs at the farm level will lead to the continuance of this practice within UK farming. The need to understand the trade-offs between environmental damage and economic performance was recognized in this work and some modelling was undertaken to explore the relationships.
A significant issue raised during the workshops with farmers was the importance of public perception in determining site location of cattle for outwintering. This aligns with several high profile debates surrounding intensification of livestock production systems and public criticism of large-scale indoor facilities. The majority of farmers in the workshops saw cattle outdoors to be associated with higher health status.
Practical recommendations for best practice
A range of best management measures and recommendations were identified from this work and then tested with farmers in a second round of workshops in the final year (2013/2014) to assess their likelihood of adoption. These were:
- Provision of visual soil assessment aids: Soil types are critically important in affecting the level of damage within a sacrifice area. If the farmer has a choice they should be on medium to heavy well-structured soils and we have developed a visual guide to understanding soil and impact on main pollutants within the context of a sacrifice field management strategy.
- Visual poaching assessment aids: A method was developed and tested to objectively measure the amount of poaching within a particular area. We are exploring options for linking this to mobile phone camera technology however, again, visual aids may be useful in identifying levels of ponding within a field at certain times of the year.
- Drainage management: Outwintering should not take place in any field which is subject to frequent ponding or surface runoff due to the inadequacy or degradation of the tile drainage system. Misiewicz (2014) has described measures for inspecting and refurbishing old field drainage systems. This might allow outwintering in a field previously unsuitable due to frequent ponding.
- Potential for rainfall collection and monitoring: In a field in which ponding occurs infrequently, there would be a benefit from recording rainfall and moving cows out of the field if the weighted mean past rainfall reaches a certain value. Only a small number of farmers (from a sample of 90) were actively recording rainfall. Investment in both collecting equipment and provision of ‘ready-reckoner’ type cards or software may be beneficial to controlling pollution in a sacrifice area.
- Use line feeding and balers: Soil compaction due to trampling leads to a significant base level of pollution which is unavoidable. We found there is no environmental benefit at all in moving the feeder to different locations periodically over the winter. Furthermore, this will cause further damage in extreme events both on the new site of the feeder ring as well as from the activity of moving this.
- Post-treatment of the field: The highest risk period emerges in the four months after sacrifice (1 April – 31 July) and N-losses are minimised if farmers reseed rather than natural regeneration. Slot seeding, which over sows, may be an option for some farmers in terms of feeding provision and minimising damage.
Farmer feedback recorded greatest support for measures 1, 2, 3 and 4.
Note also that weather provides context for these results and strategies need to be adjusted for extreme wetter winters. These may raise the issue of providing temporary shelter or the use of pads/webbing to minimise damage.
About this project
Outwintering cattle offers a number of economic benefits compared to housing over the winter months and, if the farmer is within an NVZ, offers an alternative to investing in slurry storage facilities. However, outwintering may have a number of undesirable consequences, mainly in terms of air and water pollution. In addition, there are a number of other issues related to outwintering, specifically related to economic impact, animal health and welfare, and public safety.
- To investigate the use of grass sacrifice fields.
- To explore options for mitigating negative environmental effects of outwintering.
- To hold farmer workshops to gain an insight into management and perceptions of sacrifice fields
- To develop an understanding of the limits to adoption by farmers of pollution mitigation practices.
A multidisciplinary approach will be used, with the first phase being a review of sacrifice area production systems, impacts and mitigation methods. Phase 2 involves identifying a range of at least six farms for social, economic and environmental monitoring over 2 years. Phase 3 will aim to understand the impacts on environmental and economic indicators on grassland sacrifice fields by modelling using some of the data collected from the monitor farms. The model of the consequences of sacrifice areas will look at the prediction of annual nutrient loadings in rivers and estimate land-atmosphere exchange of gaseous species, and to assess alternative management scenarios and climates.
A report will be produced at the end of project, which can lead to policy recommendations and identification of available options for mitigation. On-farm events could be held to transfer new information to the industry, which will be supported by articles and industry briefings.