Providing information on the different soil types and how to look after them is the main method by which the Tasman District Council promotes wise management of soil as a resource. Soil maps and soil descriptions are the main data sources.
There are over 140 different soil types in the Tasman Region. Different soils have different properties or characteristics.
These characteristics mean that some soils will be more suitable for certain land uses than others. For example, some areas have soils and a climate particularly suited to growing pasture grasses, and others are more suited to growing fruit trees.
Published maps and information for the district include:
These publications are available on request from Council.
New soil survey is currently being carried out by the Tasman District Council in the coastal area between Braeburn and Upper Moutere.
This survey is intended to provide better information on the soil and land versatility within rural 3 zoning, where some of the greatest development pressures exist on the Districts most versatile soils. The survey follows on from the Waimea Plains Soil Survey and is to be compiled using the same methods and sampling density, producing maps of the same scale and function.
Soil health can be affected by loss of organic matter, a breakdown of soil structure, erosion by wind and water or chemical contamination. The health of the soil influences both farm economics and the environment. To look after our soils we must know what soil characteristics are important and how to measure them. The main characteristics to assess are:
Ssoil sampling can be carried out and the results fed through the Landcare Research soil indicator tool SINDI. to help interpret soil quality.
The key soil properties that need to be measured are Olsen P, pH, mineralizable N, Total C, Total N, bulk density and macroporosity. These are standard commercial tests available through the fertiliser companies and laboratories. It is not necessary to have all 7 indicators to use SINDI but the more indicators you have, the better the resulting interpretation. SINDI is freely available onthe website:
A nutrient budget allows you to identify nutrient inputs to the farm, such as:
It also allows you to identify where nutrients go off the farm (outputs), such as:
Nutrients lost from land are a major cause of reduced water quality in our regions rivers. See the Tasman District Council surface water quality reports for further information on water quality in the district.
Nutrient budgets are just one step in effective nutrient management. Getting the fertiliser on the right place at the right time is just as important. The Code of Practise for Fertiliser Use has been produced by the fertiliser industry to guide users on all aspects of fertiliser use. The User Guides enable farmers to maximise production and minimise any adverse effects of fertiliser use.
Four User Guides cover Arable, Horticultural, Pastoral Farming and Plantation Forestry. They can be found on:
Managing nutrients carefully can save you money and improve farm decision-making. Together with soil test results, you can use a nutrient budget to assess farm fertiliser requirements, targeting nutrients where you most need them. Nutrient budgets are like financial budgets. They’re useful tools to plan ahead and keep track of what’s coming in and going out. The OVERSEER® nutrient budgeting computer programme has been developed to assist farmers. You can contact the Ministry of Agriculture and Forestry (MAF) Policy, Hamilton office, for a free copy of the OVERSEER® programme. You can also download it from:
Different farm management options available to maintain soil health include minimizing compaction and increasing the organic matter content through to reducing soil loss from erosion. Other useful information can be obtained from the following links:
The council carries out a programmeof monitoring the state of the regions soil health. This has been carried out in line with national protocol and the national programme which started in 2001.
Several soil quality characteristics are monitored. These are described in the chart below:
|
Soil quality characteristic |
Measure |
What it tells us |
Why it’s important |
|
Fertility |
Soil pH |
Whether a soil is acid or alkaline. |
Some plants and animals will only live in soils at a particular pH. |
|
|
Olsen P (phosphate) |
How much phosphate is available for plant growth. |
Phosphate (P) is an essential nutrient for plants and animals. Plants get their P from phosphates in soil. Most New Zealand soils are low in phosphates and extra phosphate needs to be added for agricultural use. |
|
Humus (organic matter) |
Total C (carbon) |
Organic matter content. |
Organic matter helps the soil store water and release it in a steady way. Organic matter also helps a soil store nutrients and form a crumbly structure suitable for plant roots. |
|
|
Total N (nitrogen) |
Organic N reserves in the soil. |
Nitrogen (N) is an essential nutrient for plants and animals. Nearly all the N in soil is in organic form (see mineralisable N). |
|
Physical condition |
Bulk density |
Whether a soil is firm and compacted or loose and friable. |
Plant roots cannot grow through compacted soil. Compacted soils also become waterlogged quickly, starving roots of oxygen. If a soil is too loose, it dries out very quickly and may be easily eroded. |
|
|
Macropores |
How many large pores there are in soil. |
Large pores (0.03–0.3 mm diameter) are needed for air to reach roots and for water drainage. The larger pores are the first to be damaged by compaction. |
|
|
Aggregate stability |
How resistant soil aggregates are to breaking. |
A stable ’crumbly’ texture lets water quickly soak into soil, doesn’t dry out too quickly, and allows roots to spread easily. This measure is most useful for soils used for horticulture and cropping. |
|
Biological activity |
Mineralisable N (nitrogen) |
How much of the total N is available to plants through microbial activity |
Mineralisable N is related to the amount and quality of organic matter and biological activity in soil. Soil life breaks down the total N in organic matter and converts it into forms plants can use. |
The latest data collected in 2009 indicate that the sampled soils were in a healthy state. Further information can be found in:
An ongoing programme of soil intactness or erosion assessment has been implemented to help identify trends and issues relating to soil disturbance and land instability in the Tasman District.
The first assessment was carried out on data collected off 2001 aerial photography. This photography covers the majority of privately owned land that may be used for land-based productive purposes. The data was collected from 6,005 points.
The survey indicates through the presence or absence of vegetation whether points are at risk of soil disturbance. It also differentiates whether disturbance results from the shifting around of soil by land use activities, or erosion and accumulation by natural processes. Finally, it assesses the extent of vegetative cover whether natural or planted ‑ and measures its effect with respect to soil conservation.
The 2001 data indicates that:
Fresh disturbance by land use related activities such as roading, cultivation, harvesting and earthworks is most intensive on dairy farms, where the majority of the disturbed area is due to the presence of farm tracks and lanes. Although the majority of dairying is based on flat land where surface water run-off is less prevalent than, say, on hill country, localised sedimentation is known to occur and affect the in-stream values of small streams. Fresh disturbance in exotic forests also is significant.
Exotic forestry is the largest commercial-based land use type situated on hill country in the survey area hence the effect of the disturbance can potentially be significant, as silt in run-off from the disturbed sites is likely to enter water bodies. The table below demonstrates the levels of disturbance.
|
Land Use |
Percentage of Survey Area |
Percentage Freshly Disturbed by Land Use |
|---|---|---|
|
Intensive land use |
1.3 |
5 |
|
Dairy pasture |
4 |
18.5 |
|
Dry stock |
15 |
6 |
|
Exotic forestry |
17 |
11.4 |
|
Scrub |
14.7 |
2.9 |
|
Native forest |
40 |
0.2 |
|
Mountain scrub/tussock |
3 |
0.4 |
The survey also indicates that there is only a low level of natural erosion through the survey area and land use is not showing up as significantly accelerating this level. More detail can be found in the Report:
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