Erosion impacts on farms. It represents a loss of current and future potential productivity on the farm and affects water quality in our streams and rivers. Financial support and plants are available for farmers from the regional council.
Approximately 252,000 hectares of Hawke’s Bay hill country has been identified as being high risk of erosion.
It is estimated that this land produces on average 3,272,686 tonnes of sediment into the region’s waterways every year. That’s 136,000 truck and trailer loads or 1090 Olympic sized swimming pools full of sediment per year.
Erosion impacts on farms. It represents a loss of current and future potential productivity on the farm. This high level of sedimentation also impacts on water quality within the region and the biodiversity (both aquatic and terrestrial) that depends upon it.
The Regional Council has a selection of poplar and willow poles for sale each year. These poles have been bred especially for farm planting.
Hawke’s Bay Regional Council had a selection of native plants for sale in 2020. These were sourced specifically for riparian planting of fenced off waterways on farms.
The ECS Scheme helps Hawke's Bay landholders keep soil on their hills and out of the water. It provides significant financial support for erosion control work such as non-commercial tree planting, fencing and land retirement. You can find out more about how we can help you on your farm by contacting your nearest catchment office.
|Case study - check out the work Horizon Farming is doing here||Case study - check out the work Evan Potter has done on his farm|
Erosion is the process where soil is lost from land. This can be driven by water or wind. Bare soil and increasing slope increases the risk of erosion. Some soils are also more susceptible.
Why this is a problem
There are a diverse range of soil types present throughout the Hawke’s Bay region. Knowledge of your properties soil types and characteristics is essential for their sustainable management and long-term agricultural profitability.
This video shows our team talking about protecting our land in Hawke's Bay
S-maps are available online here. S-map is the new national soils database. When completed, it will provide a seamless digital soil map coverage for New Zealand.
Soil maps and a soil book of the Heretaunga & Ruataniwha Plains are available. These describe soil type, characteristics, formation and ‘best management’ guidelines. Thematic maps covering available water capacity, compaction, drainage, frost, permeability and wind erosion susceptibility are also available. Call Paul Train in the Land Management Team for more details - 0800 108 838.
Across Hawke's Bay, many different types of soils have evolved. A knowledge of these soils is critical to understanding the growing environment for your trees, crops and pasture. While soils are complex, there are some basic things you need to understand.
Hawke’s Bay region is regularly affected by intense storms, and predictions are that these will increase with climate change. As well as the damage done to property, storms often cause slips on our thin soil.
Slips remove all topsoil and much subsoil leaving a very poor surface for pasture growth, and putting productive use back. The biggest challenge is replanting this lower fertility soil to return to economic production. A mix of hardy pasture species, fertiliser, soil conservation planting and careful management are needed.
This information has been prepared for farmers by the Regional Council's land management advisory team. Farmers can contact their land management advisors directly for advice for their own land.
Over-sowing and top dressing with careful management helps to improve the recovery of slip scars. Resting an erosion area for at least a season is ideal but may be difficult to achieve when feed demand arises. However the results of this work are very worthwhile as well as providing an opportunity to establish soil conservation poplar and willow poles. While many farmers may find the need to re-grass slips as soon as possible, better value may be gained by repairing fences if funds are limited.
the Regional Council's Land Management Advisors can assist with information on soil conservation planting and slip recovery. Contact us on 06 835 9200 or 0800 838 108.
Trials in the Wairarapa hill country show the recovery rate of pasture on slips can be improved by over sowing and top dressing (with at least maintenance rates of superphospate and sulphur but not nitrogen). Pasture production on these areas was 2.5 times greater after 5 years than on untreated slips.
Storms often remove all topsoil and much subsoil leaving a very poor surface for pasture growth.The biggest challenge comes back to what varieties of plants will take to this lower fertility soil types. Essentially legumes are the most successful establishers in low organic matter sites. These come in the form of white clover, sub clover, and even a touch of annual clover will be beneficial.
In terms of grasses, ryegrass will make an excellent bulker to the mix, but most likely won’t give the best persistence in this lower fertility situation. Cocksfoot will give a certain amount of success. Agri Plus recommends the following mix : Blend of Perennial Rye Grass & clover 10kg/ha; Subclover 6 kg/ha;Cocksfoot 6kg/ha; Balensa clover 4 kg/ha.
Trials in the Wairarapa suggested the following mix: Cocksfoot 6kg/ha; White Clover 3 kg/ha; Lotus pedunculatus 2kg/ha.
Plantain is another species that has the ability to cover the ground very quickly on hard sites so could be worth considering for small patches of bare ground.
There are 2 types of bare ground on hill country after a storm: slip scars and slip debris.
Slip scars are usually very hard and steep and will grass over very slowly.
Slip debris although very rough is easily converted back into high production but will include initially many weeds.
Pasture growth only reaches 70 to 80% of original production after 30 years on slip scars. Most of this recovery takes place within the first 10 years. Research has shown recovery time can be shortened by 20 years with the right management.
Sediment is soil that has been washed off the land by rain water, taking nutrients with it. Sediment has damaging impacts on water quality and the health of streams, rivers, estuaries and coastal waters.
Soil is the basis of all farming profitability and takes thousands of years to be created, so farmers benefit by doing all they can to hold soil on their land.
Sediment is no good for stream habitats and fish life. As an example most of the Tukituki Catchment has high levels of riverbed sediment. The muddy water irritates the gills of fish and invertebrates, and makes it harder for fish to find food; imagine trying to eat a sandwich sitting in a sand storm. When sediment settles, it fills the nooks and crannies that bugs and fish live in; basically taking that sandwich away! An experiment near Hamilton showed that 90% of fish left a channel after it received fine sediment deposits.
Rivers eventually flow to the sea and carry that sediment out to the coast. The Regional Council’s 2016 State of the Environment Report shows estuaries around Hawke’s Bay becoming ‘muddier’. Fine sediment accumulation can be detrimental to coastal fisheries, so reducing erosion and preventing sediment from reaching waterways in the first instance is one of the regional council’s top priorities. We are also researching the impact of sediment on our coastal fisheries.
Good margins (buffers/gaps) between waterways and productive land are critical for ecosystem health. Fencing off waterways to prevent stock entering them is essential to ensure a healthy plant barrier and also stop animals excreting in the water.
Fencing off streams, planting trees and improving ground conditions along waterways is good operational practice and land stewardship, and will help fish and bugs live happily. An experiment near Taranaki showed that removing riparian habitat resulted in 75% less inanga (the main whitebait species) in a waterway.
Nitrogen and phosphorus are both critical for plants. Farming systems aim to make the most of them because obviously it costs money to apply fert. Unfortunately, nutrients don’t always stay where they are intended and can be attached to sediment in water.
Once in waterways, nutrients can trigger excessive algal growth in both tributaries near the source and further downstream in the main river channel. Ultimately, these nutrients find their way to estuaries and the ocean which causes other problems.
Although algal growth is naturally occurring, too much algae in the water smothers habitat and reduces life-supporting capacity. It looks slimy, may smell bad and may result in Phormidium (black mat) growth, which can be toxic to people and animals.
Currently, either phosphorus or nitrogen, or both, are above target levels in waterways in most of the Tukituki catchment.
Photos: 1) long green filamentous algae 2) phormidium
E. coli in water is an indicator of disease-causing organisms associated with faeces in our waterways. People can become sick after swimming in water with bacteria and other pathogens from faeces. The regional council uses faecal source tracking as a way of figuring out what type of beast (eg. human, bird, cow) E. coli comes from.
In Hawke’s Bay faecal contamination mainly comes from livestock, and cows in particular. E. coli and other faecal bacteria can live for several weeks in water, and stay alive while being carried a long distance downstream from its source. So stock accessing and excreting in small streams a long way from swimming holes in rivers or from coastal beaches still poses a risk to human health.
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