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Sustainable farming - healthy soil

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

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