New national regulations for winter grazing need to be met by 1 May 2021. These will include changes to the way paddocks are cultivated. Having a detailed cultivation plans from your client for every paddock will ensure wintering requirements are met. Plans should include any critical source areas to avoid, waterways, paddock slope, buffers, and the required width of the buffer.
You can protect your business and your reputation by ensuring you have all the information required before you start. A conversation with your client or manager before you start cultivating a paddock will put your mind at ease and prevent any future complications.
Winter crop cultivation
Soil cultivation removes vegetation and exposes the soil to the weather, increasing the risk of soil runoff during bad weather. Nitrogen, phosphorus, soil and E. coli losses from winter forage crops are much higher than those from pasture grazed during other times of year.
A relatively small area of winter crop can make a disproportionately large contribution to nitrogen losses from the dairy farm or grazing system. The amount of N and P lost from a crop paddock can be two to seven times as much as a pasture. Too much nitrogen, phosphorus, soil or E. coli in waterways can be toxic to aquatic life, cause human health issues, contribute to excessive plant growth, and reduce recreational and aesthetic values.
The presence of slope, critical source areas (CSAs) and waterways increases the risk of sediment, E.coli and phosphorus loss to waterways. Careful management of these areas has been shown to significantly reduce losses, and uncultivated buffers around waterways act as a filter for overland flow.
Critical source areas
Critical source areas are low lying parts of farms such as gullies and swales (a shallow channel with gently sloping sides) where excess water congregates and flows, transporting soil, E. coli and phosphorus to waterways (including drains). CSAs left uncultivated will provide a filter and slow down water movement, allowing it time to soak into the soil rather than running off.
Buffer zones or grass strips in and around CSAs and next to waterways act as filters by slowing overland flow to trap suspended contaminants. The buffer should ideally be left uncultivated to operate effectively. The faster the water is flowing into a buffer zone (ie. The greater the slope of the paddock), the wider the buffer zone will need to be to provide time for effective filtering and infiltration.
Slope can be classified as good (less than 7°), not ideal (7-15°) or Steep (over 15°). Crops should only be planted on slopes that are 10° or less. If your client wishes to plant on slopes over 10° then they will require a consent. This recommendation is part of the new wintering regulations.
Creating an uncultivated buffer at the bottom of the slope will help to reduce the risk of sediment from winter crops entering the waterway. Where safe, cultivate across slopes rather than up and down. Cultivating up and down can speed up overland flow of water during heavy rainfall events.
Place bales away from waterways and CSAs. Cows will spend a lot of time around the bale which will result in greater soil damage in these areas.
Regulations around buffer widths differ between Regional Councils.
Critical source area terminology
A gully is a small but deep trench, typically on a hillside. It can be a sign of serious erosion of soil by running water.
A swale is a shallow channel with gently sloping sides; a low-lying part of a paddock that can be moist or marshy.
Buffer zones or grass strips in and around CSAs and next to waterways act as filters by slowing overland flow to trap suspended contaminants.
The buffer should ideally be left uncultivated to operate effectively. The faster the water is flowing into a buffer zone (ie. the greater the slope of the paddock), the wider the buffer zone will need to be to provide time for effective filtering and infiltration.