Converting Forestry Blocks to Pasture
The Selwyn Plantation Board Ltd and its forerunner have been growing timber trees since 1874. The Board now controls around 14,000ha of forest, and is converting 2000ha of the lower lying land to pasture to make better use of the land, and replacing this with cheaper hill country, with a higher rainfall, that is more suited to trees.
The conversion process is machinery intensive, they have imported huge specialist machines to mulch trees up to 15 years old, grind stumps and crush rocks to change the topsoil into a suitable seedbed. Along the way they have had help from Lincoln with fertiliser and pasture species advice. Various trials have been carried out and the results are being used to improve the process as they go along.
The costs involved are between $2500 and $6000 per hectare, and the process will last 18 months.
SPBL is a producer of forestry products from company-owned forest plantations located in Canterbury. The forests are predominantly radiata pine, with substantial areas of Douglas fir mainly on the Canterbury foothills. Minor plantation species include macrocarpa, Corsican pine and larch. SPBL also owns and manages land for agricultural purposes.
Currently, the company's forest products are sold on the domestic and international timber markets. The company produces mill logs (including export logs); chip logs, firewood logs, post and poles. SPBL's plantation forests have the potential to provide a sustainable supply of logs for processing at around 150,000 cubic metres annually.
The company is owned by the trading arms of the Selwyn District Council (approx 60%) and the Christchurch City Council (40%), controls about 14,000ha of freehold and leased land and has a turnover of about $12 million. Plantations are located on the Canterbury Plains, the Canterbury foothills, the coastal belt north of Christchurch, and Banks Peninsula.
SPBL has 20 employees, but on any one day there could be up 100 people operating within the resource, working in its large forest harvesting programme of about 1000-1200 tonnes per day as well as the current land conversion programme.
In the 1870s the Canterbury Plantation Board had been formed to administer some 13,000 hectares of Crown Lands to supply both shelter and wood. These reserves in the Selwyn, Ashburton and Mackenzie counties were generally narrow strips of land 2 - 300 metres wide alongside roads and scattered over the plains.
In 1885, the Canterbury Plantation Board went out of existence. Most of its reserves were vested in the Selwyn and Ashburton Counties with the remainder administered by the Lands Department. By 1910, the Selwyn County Council had established 2,100 hectares of plantation reserve.
The Selwyn Plantation Board (SPB) was established in 1910, and its powers widened in 1953. The Selwyn Plantation Board Limited (SPBL) was set up in 1989 as a Local Authority Trading Enterprise and was subsequently changed to a Council Controlled Trading Organisation.
Although the original purposes of providing shelter and timber to Christchurch are no longer necessary the company aims to be profitable for its two shareholders and carry out operations in an environmentally and socially sustainable manner.
Some sites are into their third and fourth crop of trees, each crop taking 25-30 years to mature. While this process could in theory carry on indefinitely there are some good reasons to change the land use in some areas, as Kerry Ellem, CEO of the SPBL explains:
The lack of moisture, high winds and fire risk on the Plains restricts the types of trees that can be grown. Also land values have changed considerably, so the decision was made not to replant some areas but to convert that land to an alternative use more suited to the environment than pines, says Kerry.
There are hundreds of blocks spread all over the Plains - in total about 5500 ha. Some are as small as 3ha, but one of the conversions is 400ha. These days some of the smaller ones are suitable for residential sections or lifestyle blocks on the edge of towns, and some are a suitable size for farming units.
The companys plan is to convert about 2000ha of flat land to pasture and purchase more suitable land in the foothills of Canterbury and on Banks Peninsula for forestry.
We have been going at full bore with the conversion process for about six months.
The first question was what equipment could they use to mulch trees in the ground, up to 400 stumps per ha? There were also old windrows of stumps from prior rotations to deal with. The idea was to incorporate the mulched organic material into the topsoil but it had never been done commercially in New Zealand.
The second question was could they get pastures and forage crops established on what had been a forestry operation for nearly a hundred years? What was the condition of the soil, and what would it take to get pasture established? What varieties of grass and legumes would work best?
They sourced specialist Fendt tractors and Italian equipment such as grinders, mulchers, stabilisers and rock crushers. The stumps and all of the fibrous material on the surface is mulched to little finger nail size and stones crushed so that a seedbed can be worked up, drilled and sown in pasture or crops.
With Lincolns help they laid out a 30 hectare trial block looking at different rates of fertiliser, nitrogen and lime application and different species of grass, clover, lucerne, and other forage crops.
After 10 months of trials we are starting to get a very good feel as to what is right to sow, what fertiliser application rates etc, and what form of weed control we need to be mindful of to prevent reinfestation with gorse, broom, blackberry, wattle etc, says Kerry.
Dealing with weeds is one major issue that scientists from Lincoln University have been helping with. Dr Derrick Moot, Associate Professor at Lincoln, says that raising the soil pH has helped establish the pasture species and reduce the competitiveness of woody weeds like broom and gorse. The weeds that do does emerge can be controlled when young and tender by intensity of grazingng.
It takes about 10 tonnes of lime per hectare to raise the pH from about 4.8 to 5.8, we get it on before the final preparation of the seabed is done so that the lime is incorporated into the soil profile, perhaps 30 to 50 centimetres down, says Derrick.
Superphosphate is important because sulphur and phosphate levels are usually low, and we based our recommendations for those on a soil test.
Nitrogen is also necessary to break down the woody debris. Normally cultivation releases enough nitrogen to establish pasture grasses but these soils have not been in pasture before and have a nitrogen deficit. About 100kgN/ha is applied on some soils to boost the woody material breakdown and pasture establishment.
The ultimate goal is to produce either a pasture or a lucerne stand. We told SPBL that we wanted an area where we could try a few crazy things and from those we could give them our best recommendations, for the large commercial areas he says.
At Darfield we set up a comparison of going through brassica crops or cereal crops before pasture, or both brassica and the cereal crop before pasture, compared with going straight into the pasture without a crop. This has given us an opportunity to have a couple of shots at the weed control issue.
Incorporating the mulched material into the soil rather than burning it has given several benefits, according to Kerry Ellem better moisture retention in a dry summer and a slightly higher soil temperature in winter. They have also found that there is a best sequence of crops that will improve soil structure and ultimately lead to a better pasture.
About 2000ha will be converted over the next 18 months. This is a one-off operation, and after that the company will focus on growing and harvesting forests sustainably on land that is more suited to this purpose.
The conversion process is machinery intensive, they have imported huge specialist machines to mulch trees up to 15 years old, grind stumps and crush rocks to change the topsoil into a suitable seedbed. Along the way they have had help from Lincoln with fertiliser and pasture species advice. Various trials have been carried out and the results are being used to improve the process as they go along.
The costs involved are between $2500 and $6000 per hectare, and the process will last 18 months.
SPBL is a producer of forestry products from company-owned forest plantations located in Canterbury. The forests are predominantly radiata pine, with substantial areas of Douglas fir mainly on the Canterbury foothills. Minor plantation species include macrocarpa, Corsican pine and larch. SPBL also owns and manages land for agricultural purposes.
Currently, the company's forest products are sold on the domestic and international timber markets. The company produces mill logs (including export logs); chip logs, firewood logs, post and poles. SPBL's plantation forests have the potential to provide a sustainable supply of logs for processing at around 150,000 cubic metres annually.
The company is owned by the trading arms of the Selwyn District Council (approx 60%) and the Christchurch City Council (40%), controls about 14,000ha of freehold and leased land and has a turnover of about $12 million. Plantations are located on the Canterbury Plains, the Canterbury foothills, the coastal belt north of Christchurch, and Banks Peninsula.
SPBL has 20 employees, but on any one day there could be up 100 people operating within the resource, working in its large forest harvesting programme of about 1000-1200 tonnes per day as well as the current land conversion programme.
In the 1870s the Canterbury Plantation Board had been formed to administer some 13,000 hectares of Crown Lands to supply both shelter and wood. These reserves in the Selwyn, Ashburton and Mackenzie counties were generally narrow strips of land 2 - 300 metres wide alongside roads and scattered over the plains.
In 1885, the Canterbury Plantation Board went out of existence. Most of its reserves were vested in the Selwyn and Ashburton Counties with the remainder administered by the Lands Department. By 1910, the Selwyn County Council had established 2,100 hectares of plantation reserve.
The Selwyn Plantation Board (SPB) was established in 1910, and its powers widened in 1953. The Selwyn Plantation Board Limited (SPBL) was set up in 1989 as a Local Authority Trading Enterprise and was subsequently changed to a Council Controlled Trading Organisation.
Although the original purposes of providing shelter and timber to Christchurch are no longer necessary the company aims to be profitable for its two shareholders and carry out operations in an environmentally and socially sustainable manner.
Some sites are into their third and fourth crop of trees, each crop taking 25-30 years to mature. While this process could in theory carry on indefinitely there are some good reasons to change the land use in some areas, as Kerry Ellem, CEO of the SPBL explains:
The lack of moisture, high winds and fire risk on the Plains restricts the types of trees that can be grown. Also land values have changed considerably, so the decision was made not to replant some areas but to convert that land to an alternative use more suited to the environment than pines, says Kerry.
There are hundreds of blocks spread all over the Plains - in total about 5500 ha. Some are as small as 3ha, but one of the conversions is 400ha. These days some of the smaller ones are suitable for residential sections or lifestyle blocks on the edge of towns, and some are a suitable size for farming units.
The companys plan is to convert about 2000ha of flat land to pasture and purchase more suitable land in the foothills of Canterbury and on Banks Peninsula for forestry.
We have been going at full bore with the conversion process for about six months.
The first question was what equipment could they use to mulch trees in the ground, up to 400 stumps per ha? There were also old windrows of stumps from prior rotations to deal with. The idea was to incorporate the mulched organic material into the topsoil but it had never been done commercially in New Zealand.
The second question was could they get pastures and forage crops established on what had been a forestry operation for nearly a hundred years? What was the condition of the soil, and what would it take to get pasture established? What varieties of grass and legumes would work best?
They sourced specialist Fendt tractors and Italian equipment such as grinders, mulchers, stabilisers and rock crushers. The stumps and all of the fibrous material on the surface is mulched to little finger nail size and stones crushed so that a seedbed can be worked up, drilled and sown in pasture or crops.
With Lincolns help they laid out a 30 hectare trial block looking at different rates of fertiliser, nitrogen and lime application and different species of grass, clover, lucerne, and other forage crops.
After 10 months of trials we are starting to get a very good feel as to what is right to sow, what fertiliser application rates etc, and what form of weed control we need to be mindful of to prevent reinfestation with gorse, broom, blackberry, wattle etc, says Kerry.
Dealing with weeds is one major issue that scientists from Lincoln University have been helping with. Dr Derrick Moot, Associate Professor at Lincoln, says that raising the soil pH has helped establish the pasture species and reduce the competitiveness of woody weeds like broom and gorse. The weeds that do does emerge can be controlled when young and tender by intensity of grazingng.
It takes about 10 tonnes of lime per hectare to raise the pH from about 4.8 to 5.8, we get it on before the final preparation of the seabed is done so that the lime is incorporated into the soil profile, perhaps 30 to 50 centimetres down, says Derrick.
Superphosphate is important because sulphur and phosphate levels are usually low, and we based our recommendations for those on a soil test.
Nitrogen is also necessary to break down the woody debris. Normally cultivation releases enough nitrogen to establish pasture grasses but these soils have not been in pasture before and have a nitrogen deficit. About 100kgN/ha is applied on some soils to boost the woody material breakdown and pasture establishment.
The ultimate goal is to produce either a pasture or a lucerne stand. We told SPBL that we wanted an area where we could try a few crazy things and from those we could give them our best recommendations, for the large commercial areas he says.
At Darfield we set up a comparison of going through brassica crops or cereal crops before pasture, or both brassica and the cereal crop before pasture, compared with going straight into the pasture without a crop. This has given us an opportunity to have a couple of shots at the weed control issue.
Incorporating the mulched material into the soil rather than burning it has given several benefits, according to Kerry Ellem better moisture retention in a dry summer and a slightly higher soil temperature in winter. They have also found that there is a best sequence of crops that will improve soil structure and ultimately lead to a better pasture.
About 2000ha will be converted over the next 18 months. This is a one-off operation, and after that the company will focus on growing and harvesting forests sustainably on land that is more suited to this purpose.