Comparing key soil quality characteristics against threshold values tells us whether soil quality is satisfactory for different land use activities within our region. National guidelines have been developed to take into account different soil types. Land use activities consider both production and environmental goals.
Target ranges for individual soil characteristics were assessed using 'SINDI'. This is a web-based tool designed by Landcare Research to help interpret the quality of a soil that has been sampled. To find out more about how the national soil guidelines were developed, see Landcare Research’s soil indicators tool SINDI.
Soil Quality in the Marlborough Region
The Marlborough District Council began to monitor soil quality in the region in 2000. Between 2007 - 2012, 118 sites were sampled, with more sites yet to be sampled. Sites sampled represent a range of different land use activities including vineyards, cropping, pasture, dairy, native bush and exotic forest representing the major soil orders in the region.
To obtain reliable, long-term detection and prediction of trends in soil quality, at least three and preferably five points along a time sequence should be obtained. While results at this stage are very insightful, they only provide a snapshot of soil quality under different land use activities in Marlborough.
Keys finding include:
- Some cropping sites sampled showed signs of physical soil deterioration including low macro-porosity, low aggregate stability and low total carbon
- Some dairy pasture sites sampled had elevated soil fertility and soil compaction
- Some vineyards soil showed soil compaction in their inter-rows
- Trace element concentrations in soils were generally low and were similar to concentrations found in other parts of New Zealand
Maintaining Good Soil Quality
It makes sense to look after your soils – not only from an environmental point of view but also because healthy soils are central to plant growth and maintaining and enhancing agricultural and horticultural production. There are a number of things you can do to help maintain and enhance soil quality.
1) Getting your soil fertility right
To help maintain optimal soil fertility levels to meet your production goals, you need to undertake regular soil testing on different parts of your property to check nutrient levels. To ensure you are putting on the appropriate amount of fertiliser for your soil and production needs, you should undertake a nutrient budget. This can obtained from your fertiliser representative using a nutrient budget model such as OVERSEER®.
2) Maintaining soil organic matter
- To maintain or increase the organic matter in your cropping soil, grow annual cover crops between productive crops – these cover crops can then be mulched into the ground.
- You could also apply compost, organic manure or effluent to the soil. With more organic matter, soil is better able to store nutrients and water and has better soil structure.
- Reduce cultivation and soil disturbance to minimise the loss of organic matter – try direct drilling of seed for pasture renewal.
3) Looking after soil structure
Pugging and compacting of your soil can result in poor water infiltration which may increase overland flow and the potential for nutrient losses from soils. It may also result in poor drainage, gas exchange and subsequent crop production. To protect your soil from pugging and compaction:
- Graze wetter paddocks before the wetter part of the season
- Build pasture cover leading in to the wet season, to give better protection against pugging
- Graze land that is at risk of pugging with light stock
- Use the farm bike rather than heavy tractors
- Vary the depth of cultivation annually – to avoid forming a plough plan
- Avoid working the soil when it is wet