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:
- amount of organic matter
- physical condition (for example, whether it has become compacted)
- amount of beneficial soil life, such as bacteria and earthworms.
Soil Health On-Farm Assessment
On the farm soil health can be assessed using the Visual Soil Assessment (VSA) tool. This tool was developed by Landcare Research, provides landowners with simple tools to check their soil’s physical condition. The VSA booklets are available from the Tasman District Council free of charge and Tasman District Council staff are available to assist with getting you started and developing an “on the farm” assessment programme. Further information can be obtained from:
Alternatively, soil 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:
- purchased feed
- clover nitrogen (N) fixation
- Dairy shed effluent
It also allows you to identify where nutrients go off the farm (outputs), such as:
- farm products – for example, milk, wool, meat
- transfer to non-productive areas - for example, races, stock camps, yards
- leaching and runoff losses to waterways
- gaseous losses to the air.
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:
How to Look After Our Soils
The VSA booklets also outline the different farm management options available to maintain soil health. These include minimizing compaction, increasing the organic matter content through to reducing soil loss from erosion. Other useful information can be obtained from the following links: