Development of the peat.
To understand the problems of farming peat you need to understand how peat was formed and it’s different stages of development. Peat is formed from the remains of wetland plants in wet environments. The high water tables prevent the rapid breakdown of the dead plant material. On Craigmore the peat is called “oligotrophic” as it forms where rainwater is the source. Because rainwater doesn’t contain many nutrients oligotrophic peats have a low fertility and are acidic. They generally support low-growing plants tolerant of low fertility such as sphagnum moss.
The Waikato peatlands began to form about 18000years ago when the Waikato river changed course. The river filled the basin with debris, which built up into a series of gravel fans. Drainage was poor in between the fans, resulting in wet patches and small ponds where peat formed. The peat spread out, merged into a basin bog and domes began to develop from sedges and rushes. As the peat spread outwards, it covered trees growing on the higher parts of the fans. It is the stumps and logs from these that are such a problem to us when managing the peat land today.
Undeveloped peat is mostly made up of organic matter and a small amount of mineral material. As the peat is developed, it shrinks and becomes denser. Developed peat has a higher bulk density than the undeveloped peat, contains less organic matter and more mineral matter. Development for pasture usually requires inputs of nitrogen and lime. As a result the pH increases and the carbon to nitrogen ratio decreases. This relatively high carbon content gives peat a good physical structure for growing.
In 1943 at Craigmore 976 acres of undeveloped peat was purchased. This peat ranged from 20 to 80 feet deep. This was some of the deepest in the Waikato. The land was broken in the 1960s and started with a pH of 3.3. The land was broken in by digging in drains, the teatree and moss was dried out and ran over with a bulldozer on big swamp tracks. This was then burnt. The biggest problem was keeping the bulldozer afloat, as it was so wet.
Today careful management of the peat is still needed so that it keeps improving. The peat at Craigmore can now be described as semi improved peat to improved.
Some of the key actions we do are:
- Stumping – paddocks are still being cleared of the logs and stumps that keep coming up to the surface. These logs are very costly to remove and machinery can get damaged when working the ground. When the logs are removed they are put into a stack and burnt. The logs are manly kahikatea. When these heaps are burnt we need to be careful that the peat underneath them does not burn for too long otherwise you are left with big holes in the ground. Fires can burn for a very long time on the fibre that is in the ground.
- Drainage – drainage is an on going cost due to replacing broken and blocked culverts, and when they become to high as the peat shrinks. On-going cleaning is needed of the drains. We also spray the drains to try and keep them clean.
- Lime – we are always putting on lime to try and keep the pH up. As the peat shrinks we rotary hoe/ disc plough it that brings up more raw peat which causes us to have to put more lime on.
- Fertiliser – we need to continue to add fertiliser to the peat ground to keep up fertility.
- Minerals – copper and selenium are added to the fertiliser to try and compensate for the lack of minerals in the peat. Additional minerals are given to the cattle as outlined in the animal health section.
- Fencing – we have started using 5 metre strainers and electric fencing because with the ground shrinking and soft we find the 5 metre strainers hold the wire up better and gates stay swinging longer.
- Tracks –the tracks were formed in the 1970s which took a lot of clay to give a solid base with 2 drains down each side, which was slow progress, because we couldn’t get big gear across the ground.
- Stock in drains –we always need to check the drains in the paddocks the stock are in and have to pull them out regularly. If we have a water leak the problem is even worse as the animals go to the drain to drink and can’t get out. We try and calve our cows in paddocks that don’t have drains for this reason. We lose a few calves every year by falling in the drains.
- Weeds growing between fence and drain –we have to keep spraying especially for blackberries.
This all results in huge additional costs compared with farming on better soils, however farming peat was a challenge for my grandfather, father and now my generation to get the peat to a stage where it is more productive. The challenge and enjoyment is seeing it improve greatly over the short time it has been worked.
DAVID & SUE HENDERSON
PH: 07 825 2677
MOB: 021 166 1389
429 RUKUHIA ROAD, RD2, OHAUPO