Each of the LRI polygons was assigned a Class, Subclass and Unit, wherever possible regional LUC are used to help classify the Reureu LUC. The Reureu blocks lie within the ‘Taranaki – Wanganui Region LUC classification’ (Fletcher, 1987), which was therefore used to help assign an LUC to each polygon.
The class of each polygon was chosen based on the ‘Land-use Capability Survey Handbook’ (Lynn et al., 2009) and the ‘Taranaki – Wanganui LUC classification’ (Fletcher, 1987). The subclass chosen was based on the dominant limiting factor, if two were present than as stated in the ‘Land-use Capability Survey Handbook’ (Lynn et al., 2009) the priority allocation was given. The unit (i.e. severity of limitation) for each polygon was assigned based on similar regional units.
Each of the LUC units is explained in further detail below. The LUC suite and sub-suite used are those which are referred to in the ‘Taranaki – Manawatu Region Land-use Capability Handbook’ (Fletcher, 1987).41
The LUC classes are explained as an extended legend to help identify blocks and differentiate between different management types. The Pinus radiatasite index is based on the Taranaki – Manawatu Region Extended Legend’ (Fletcher, 1987) information.
The following outlines site index based on height in metres of Pinus Radiata at 20 years old:
x Very high >35, High 30-35, Medium 25-29, low, 20-24 and Very low <20
The Reureu blocks have a total area of LUC Class 2 land of 29ha and LUC Class 3 land of 43ha.
C h apt er 5 – R es u lt s
LUC unit: ȱȱV
(8.6 ha)
LUC suite: 5. Loess
LUC sub suite: 5a
Description: Flats located on slightly higher terrace away from frequent flooding formed from alluvial deposits. Flat to gently undulating terraces.
Slope: 0 - 3° (A)
Rock Type: Alluvial Gravels (Gr)
Soil: Manawatu deep silt loam
Manawatu moderately deep silt loam Karapoti silt loam
Erosion: Present: Negligible to slight (mostly negligible) deposition, slight soil slip
Potential: Slight deposition, slight to moderate soil slip
Vegetation: Improved Pasture (gI)
Land-use: Present: Undeveloped, pastoral grazing
Agriculture Potential: Intensive pastoral grazing, dairying cropping, root and green fodder crops.
Forestry Potential: Production (site index P. radiate 29- 34)
Management: Apply fertiliser to achieve higher production levels. Possible addition of subsurface drainage to achieve high levels of cropping and pastoral production might be required. Those soils which lie close to the stream should have stream bank protection. Limitation poor soil structure and poor internal soil drainage. Shelter belts required for horticulture.
Comments: Slight limitation due to soil conditions. These soils can still be flooded, therefore protection from nearby waterways would be recommended.
LUC unit: ȱȱZ
(14.9 ha)
LUC suite: 5. Loess
LUC sub suite: 5a
Description: Flats located on slightly higher terrace away from frequent flooding formed from alluvial deposits.
Slope: 0 - 3° (A)
Rock Type: Alluvial Gravels (Gr)
Soil: Rangitikei deep silt loam
Manawatu deep silt loam
Erosion: Present: Negligible Stream bank, negligible deposition
Potential: Slight Stream bank, negligible to slight deposition
Vegetation: Improved Pasture (gI)
Land-use: Present: Undeveloped, pastoral farming
Agriculture Potential: Intensive pastoral grazing, dairying cropping, cereal cropping, root and green fodder cropping, horticulture.
Forestry Potential: Production (site index P. radiate 33-35)
Management: The stream banks will need to be protected to ensure soil loss is minimal, planting along the stream may be beneficial. These soils suffer from soil wetness, from occasional flooding, gleying and presence of mottles. However these soils have a good soil depth 45-90 cm. Shelter belts required for horticulture.
Comments: Soils close to streams need to be protected. Soils in this category have continued wetness limitation after drainage.
LUC unit: ȱȱZ
(5.5 ha)
LUC suite: 5. Loess
LUC sub suite: 5a
Description: Flats located on slightly higher terrace away from frequent flooding formed from alluvial deposits
Slope: 0 - 3° (A)
Rock Type: Alluvial Gravels (Gr)
Soil: Rangitikei deep silt loam over sand
Rangitikei deep silt loam over sand Rangitikei deep sandy loam
Erosion: Present: Negligible to slight (mostly negligible) deposition
Potential: Slight deposition
Vegetation: Improved Pasture (gI)
Land-use: Present: Undeveloped, pastoral grazing
Agriculture Potential: Intensive pastoral grazing, dairying cropping, root and green fodder cropping
Forestry Potential: Production (site index P. radiate 23-26)
Management: The soils are quite free draining soils, therefore may need to be irrigated during the summer months. These soils suffer from the possibility of frequent flooding.
Comments: To achieve maximum production, fertiliser application and irrigation will be required. Soils have a slight limitation due to the wetness of the soils and poor internal drainage. Drainage systems will need to be in place to maximise production values.
LUC unit: ȱȱȱV
(0.9ha)
LUC suite: 5. Loess
LUC sub suite: 5a
Description: Flats located on lower terrace formed by alluvial deposits, close to stream.
Slope: 0 - 3° (A)
Rock Type: Alluvial Gravels (Gr)
Soil: Manawatu deep silt loam over sand
Manawatu deep sandy loam
Erosion: Present: Negligible to slight deposition
Potential: Slight to moderate deposition
Vegetation: Improved Pasture (gI)
Land-use: Present: Undeveloped, pastoral grazing
Agriculture Potential: Intensive pastoral grazing, cropping, dairying, horticulture, cereals, root and green fodder crops.
Forestry Potential: Production (site index P. radiate 29-32)
Management: The soils have moderate soil depths, with the presence of stones above 45 cm, but below 20 cm, limiting their versatility. The nearby stream has also the possibility of depositing alluvial deposits across these soils.
Comments: Subsurface drainage may be required and protection from the nearby stream to avoid alluvial deposits. Seasonal soil moisture deficits limit versatility. Shelterbelts required for horticultural use.
LUC unit: ȱȱȱV
(0.3ha)
LUC suite: 5. Loess
LUC sub suite: 5a
Description: Flats located on lower terrace formed by alluvial deposits, close to stream.
Slope: 0 - 3° (A)
Rock Type: Alluvial Gravels (Gr)
Soil: Rangitikei moderately deep sandy loam
Manawatu shallow silt loam
Erosion: Present: Negligible to slight deposition
Potential: Slight to moderate deposition
Vegetation: Improved Pasture (gI)
Land-use: Present: Undeveloped, pastoral grazing
Agriculture Potential: Intensive pastoral grazing, cropping, dairying horticulture, cereals, root and green fodder crops.
Forestry Potential: Production (site index P. radiate 23-26)
Management: The soils have moderate soil depths, with the presence of stones above 30 cm, limiting their versatility. The nearby stream has also the possibility of depositing alluvial deposits across these soils. The presence of stones is 15- 35% between 20–45 cm.
Comments: Subsurface drainage may be required and protection from the nearby stream to avoid alluvial deposits. Also the nearby South hill may need to be stabilised in the future.
LUC unit: ȱȱȱV
(3.8 ha)
LUC suite: 5. Loess
LUC sub suite: 5a
Description: Flats located on lower terrace formed by alluvial deposits, close to Rangitikei River.
Slope: 0 - 3° (A)
Rock Type: Alluvial Gravels (Gr)
Soil: Otaki silt loam
Rangitikei shallow silt loam Rangitikei shallow sandy loam Otaki sandy loam
Erosion: Present: Negligible to slight deposition, Moderate Stream bank erosion
Potential: Slight to moderate deposition, Moderate stream bank erosion
Vegetation: Improved Pasture (gI)
Land-use: Present: Undeveloped, pastoral grazing
Agriculture Potential: Pastoral Grazing (intensive with careful management), intensive grazing, dairying
Forestry Potential: Production (site index P. radiate 27-29)
Management: The soils here have 40-70% stones present in the top 20 cm, which limits their ability to be cultivated. The Otaki soils will also drain excessively, so management of nutrient loss will need to be monitored.
Comments: Irrigation for these soils during the summer months will be required to achieve maximum production.
LUC unit: ȱȱȱZ
(10.4 ha)
LUC suite: 5. Loess
LUC sub suite: 5a
Description: Flats located on lower terrace formed by alluvial deposits, close to Rangitikei River and stream.
Slope: 0 - 3° (A)
Rock Type: Alluvial Gravels (Gr)
Soil: Rangitikei deep silt loam
Rangitikei deep sandy loam
Rangitikei deep silt loam over sand
Erosion: Present: Negligible to slight deposition
Potential: Slight to moderate deposition
Vegetation: Improved Pasture (gI)
Land-use: Present: Undeveloped, pastoral grazing
Agriculture Potential: Pastoral Grazing (intensive with careful management), intensive dairying, vegetable cropping, root and green fodder cropping.
Forestry Potential: Unsuitable
Management: The soils have frequent flooding events which can occur, slow internal drainage and low water holding capacities. Cropping can be affected if frequent flooding and excessive rainfall in some areas.
Comments: Irrigation for these soils during the summer months will be required to achieve maximum production. Cropping versatility is restricted by wetness of soils.
LUC unit: ȱȱȱZ
(29 ha)
LUC suite: 5. Loess
LUC sub suite: 5a
Description: Flats located on lower terrace formed by alluvial deposits, close to Rangitikei River and stream.
Slope: 0 - 3°
Rock Type: Alluvial Gravels (Gr)
Soil: Parewanui deep silt loam
Parewanui deep sandy loam Kairanga clay loam
Erosion: Present: Negligible to slight deposition
Potential: Slight to moderate deposition
Vegetation: Improved Pasture (gI)
Land-use: Present: Undeveloped, pastoral grazing
Agriculture Potential: Pastoral Grazing (intensive with careful management) intensive dairying.
Forestry Potential: Production (site index P. radiate 30 -33)
Management: The soils have frequent flooding events which can occur, slow internal drainage and low water holding capacities. The Parewanui Soil has very poor drainage; careful management of these soils in terms of nutrient loss will need to be managed. Control water table.
Comments: Irrigation for these soils during the summer months will be required to achieve maximum production. High water table during winter and spring limits cropping production.
5.3.1
LUC Leaching Limits
Horizons Regional Council has set limits on the amount of nitrogen leaching allowed and is measured in kgN/ha/yr.
The Nitrogen leaching allowance is as follows:
x Year 1 – 25 kgN/ha/yr
x Year 5 – 22 kgN/ha/yr
x Year 10 – 20 kgN/ha/yr
x Year 20 – 19 kgN/ha/yr
(HRC, P. Taylor, personal communication, 2014).
The total leaching allowance for the Reureu blocks are given (Table 27). (HRC, P. Taylor, personal communication, 2014).
The Reureu blocks show that overall the biggest limitation over the 74 ha, is a soil factor with 43 ha of the total area having a presence of stones within the top 20 cm of the soil profile which limit the versatility. The only other limitation on the Reureu blocks is soil wetness. Wetness in the Reureu case is due to the frequent flooding events, slow internal drainage, presence of mottles and gleying. Management of these two limitations will need to be taken into account to determine the best possible land- use, taking into account the nitrogen leaching amounts.
Table 27 >ĞĂĐŚŝŶŐ>ŝŵŝƚƐĨŽƌZĞƵƌĞƵďůŽĐŬƐĂƐƉĞƌ>hĐůĂƐƐ
Year LUC 2 LUC 3 Total
Ha 29 43 72
1 783 1080 1863
5 725 945 1670
10 638 855 1493