In a nutshell...
- Soil health is not easy to define, but it is vital to the health of the plants that grow in it, and the animals that graze it.
- Many believe that it's also the basis of consumer health and welfare.
- The concept of a "living soil" is real and describes the large amount of micro organisms in the soil.
- For example there are 1600kg/ha of bacteria, 2000kg/ha of fungi and 800kg/ha of earthworms.
- Healthy soils are fertile and rich in organic matter and humus, have a good crumb structure and are porous.
- Organic farmers make soil health their prime focus.
How can you tell if you have a problem?
- When you dig a spade spit and try to break the soil with your hands, it does not show a crumb structure with long plant roots.
- It is highly compacted and solid, with shallow roots.
- There may be evidence of a "pan" or compaction layer a few cm below the surface, preventing root penetration.
- Water will not drain through the soil and lies in puddles for a long time after heavy rain.
- Tile or mole drain outlets are not running after rain.
- Poor pasture grows all year round, with no clear spring flush.
- No earthworm casts on the surface and less than 2 worms/spade spit.
- Low levels of organic matter in the soil.
- A build up of a layer of dead organic matter on the soil surface.
- Soil does not smell pleasantly earthy - it smells sour.
- Presence of low-fertility grass species and very little clover.
- Presence of weeds - especially those that thrive in low fertility.
- Increased water runoff after rain - seen from sediment in drains and creeks.
How can you tell if you're doing well?
- When you did a spade spit, the soil is moist, has a pleasant earthy smell (not sour).
- You can break the dug spit with your hands to see a nice crumb structure.
- You can see plenty of organic matter and long healthy plant roots.
- There are healthy active earthworms in burrows in the soil.
- There is no sign of a pan below the soil surface.
- There is no accumulation of organic matter on the surface - earthworms have taken it all below ground.
- The pastures are made up of high fertility species of grasses and clovers, and they look healthy and not stunted.
- There is good pasture growth all year round, especially in spring.
- Drains are working and there are no areas where water remains stagnant after rain.
- There is no pugging in wet weather.
- Livestock look healthy and are being well fed.
What can you do to improve things?
- Treat the soil as the most precious part of the farm. Don't call soil "dirt"!
- Remember that maintaining the micro-organisms in the soil is vital to healthy crops and livestock.
- Maintain soil fertility to meet the demands of your farming system.
- Soil test regularly and carry out recommendations resulting from the tests.
- Remember the importance of lime (not technically a fertiliser)
- Keep a strict control on nitrogen fertiliser and only use it strategically.
- Likewise, be careful with farm effluent and get it analysed to see what nutrients are being applied.
- Think of a nutrient balance sheet for each paddock where inputs and outputs are measured and must balance. This concept is being adopted now.
- Avoid pugging pastures with stock on wet weather.
- Avoid cultivating soils that are too wet or too dry.
- Introduce new pasture species and cultivars that suit your farming needs.
- Don't overgraze to expose the soil surface to the sun and rain.
- Observe weeds as indicators of the effect of management on the soil.
- Install, maintain and improve drainage. (See drainage)
- If pastures have to be renovated at frequent intervals, check the reasons why.
- If there is a lot of pasture pulling, then look at soil structure and health.
Where can you go for help?
- Regional Councils
- County Councils
- Federated Farmers of NZ
- Ministry of Agriculture and Forestry
- Department of Conservation
Dr Richard Chapman, Soil Consultant. Phone (07) 829-5437