5.7.4 Soil Fertility
Following drainage of Gley Soils, pasture or crop production
is supported from the natural soil fertility and good yields
can be obtained. However, the initial flush of productivity
will not last as nutrients are exported with the farm products
and hence establishment of sustainable farm production
systems requires fertiliser input to maintain soil nutrient
levels.
Acid Gley Soils have a subsoil pH
4.8 and generally
occur in areas of high rainfall. The soils may be strongly
weathered and strongly leached and in such cases natural
fertility is low. Inputs of lime and other fertilisers will
improve productivity. Development of the soils for
acid-sensitive deep rooting plants may be precluded. Nitrogen requirements are likely to be higher than in associated
well drained soils.
5.7.5 The Value of Wetlands—Their
Maintenance and Enhancement
Manaaki Whenua – Landcare Research has shown that about
85% of New Zealand’s original wetland areas, which comprise Gley Soils, along with Organic Soils (Chap. 8), have
been drained and developed for agricultural production. In the
Bay of Plenty Region, only about 7.7% of the wetlands remain
in an unmodified state. Land drainage has led to a range of
ecological changes including loss of habitat for a number of
rare or endangered species. There may also be wider effects,
for example, the reduced incidence of fog in the Hamilton area
of the central Waikato basin has been attributed to the drainage of wetlands. Although many drained wetlands are agriculturally productive, the loss of such large tracts of wetlands
(which more broadly include fens and bogs as well as
swamps) is now lamented by many because wetlands have
been recognised as having a range of important values
including supporting a wide range of biodiversity. Wetlands
can reduce flood peaks as they absorb and hold water,
releasing it slowly to keep streams flowing in dry periods.
Wetlands trap suspended sediments and nutrients, and may
convert up to 90% of nitrogen in runoff to nitrogen gas,
returning it to the atmosphere, and thus preventing eutrophication of downstream water bodies. Wetlands may also be
effectively designed and managed to treat wastewaters.
In many areas there is value in maintaining and restoring
wetlands. The first step in protecting wetlands is to ensure
that adjacent drainage is not going to lower the water table of
the wetland. This may mean a weir or high-level culvert is
needed to control the water level. To protect wetland vegetation and prevent damage to ground surfaces and wetland
margins, it is preferable to prevent stock (especially cattle)
access. However, in some instances light grazing by sheep
can be effective for weed control. Replanting areas with
suitable native wetland plants can increase the rate of
recovery. A number of nurseries provide a range of suitable
plant material and excellent advice on what would be suitable for a particular site. Until wetland plants have achieved
canopy closure, ongoing weed control is likely to be needed
to prevent invasive weeds including privet and blackberry,
among others, from taking over.
Further Reading
Adcock I (1973) A goodley heritage. Eketahuna and districts 100 years
1873–1973. Eketahuna Borough and County Councils. 354 p
Ausseil A-G, Gerbeaux P, Chadderton WL et al (2008) Wetland
ecosystems of national importance for biodiversity: criteria, methods and candidate list of nationally important inland wetlands.
Landcare Research Contract Report LC0708/158 for the Department of Conservation, 162 p
Ausseil A-GE, Chadderton WL, Stephens RTT et al (2011) Applying
systematic conservation planning principles to palustrine and inland
saline wetlands of New Zealand. Freshw Biol 56(1):142–161
Belliss S, Shepherd J, Newsome P et al (2017) An analysis of wetland
loss between 2001/02 and 2015/16. Landcare Research Contract
Report LC2798 for the Ministry for the Environment, 37p. Birkeland PW (1999) Soils and gneomorphology, 3rd ed. Oxford Univ.
Press, New York, 429 p
Bouma J (1983) Hydrology and genesis of soils with aquic moisture
regimes. In: Wilding LP, Smeck NE, Hall GF (eds) Pedogenesis and
Soil Taxonomy: I. Concepts and interactions. Dev Soil Sci 11:253–
281
Childs CW (1981) Field tests for ferrous iron and ferric-organic
complexes (on exchange sites or in water-soluble forms) in soils.
Aust J Soil Res 19:175–180
Childs CW (1992) Ferrihydrite: a review of structure, properties and
occurrence in relation to soils. Zeitschrift für Pflanzenernährung und
Bodenkunde 155:441–448
Childs CW, Palmer RWP, Ross CW (1990) Thick iron oxide pans in
soils of Taranaki, New Zealand. Aust J Soil Res 28:245–257
Churchman GJ, Lowe DJ (2012) Alteration, formation, and occurrence
of minerals in soils. In: Huang PM, Li Y, Sumner ME (eds) Handbook of soil sciences, 2nd edn. Vol. 1: Properties and Processes.
CRC Press, Boca Raton, pp 20.1–20.72
Clarkson BR, Ausseil AE, Gerbeaux P (2013) Wetland ecosystem
services. In: Dymond K (ed) Ecosystem services in New Zealand—
conditions and trends. Manaaki Whenua Press, Lincoln, pp 192–
202
Cowie JD (1978) Soils and agriculture of Kairanga County. NZ DSIR
Soil Bureau Bulletin 33. 92 p
Dent DL (1978) Saline gley soils and acid sulphate soils. In: Soil
groups of New Zealand Part 3 gley soils. New Zealand Society of
Soil Science. 127 p
Fitzpatrick RW, Taylor RM, Schwertmann U et al (1985) Occurrence
and properties of lepidocrocite in some soils of New Zealand, South
Africa and Australia. Aust J Soil Res 23:543–567
Gibbs M (2007) Best practices environmental guidelines—land
drainage. Environment Waikato. 33p. ISSN:1772-4005
Hewitt AE (1993) Methods and rationale of the New Zealand Soil
Classification. Landcare Research Science Series No. 2. Manaaki
Whenua Press, Lincoln, New Zealand. 71 p
84
5 Gley Soils
Following drainage of Gley Soils, pasture or crop production
is supported from the natural soil fertility and good yields
can be obtained. However, the initial flush of productivity
will not last as nutrients are exported with the farm products
and hence establishment of sustainable farm production
systems requires fertiliser input to maintain soil nutrient
levels.
Acid Gley Soils have a subsoil pH
4.8 and generally
occur in areas of high rainfall. The soils may be strongly
weathered and strongly leached and in such cases natural
fertility is low. Inputs of lime and other fertilisers will
improve productivity. Development of the soils for
acid-sensitive deep rooting plants may be precluded. Nitrogen requirements are likely to be higher than in associated
well drained soils.
5.7.5 The Value of Wetlands—Their
Maintenance and Enhancement
Manaaki Whenua – Landcare Research has shown that about
85% of New Zealand’s original wetland areas, which comprise Gley Soils, along with Organic Soils (Chap. 8), have
been drained and developed for agricultural production. In the
Bay of Plenty Region, only about 7.7% of the wetlands remain
in an unmodified state. Land drainage has led to a range of
ecological changes including loss of habitat for a number of
rare or endangered species. There may also be wider effects,
for example, the reduced incidence of fog in the Hamilton area
of the central Waikato basin has been attributed to the drainage of wetlands. Although many drained wetlands are agriculturally productive, the loss of such large tracts of wetlands
(which more broadly include fens and bogs as well as
swamps) is now lamented by many because wetlands have
been recognised as having a range of important values
including supporting a wide range of biodiversity. Wetlands
can reduce flood peaks as they absorb and hold water,
releasing it slowly to keep streams flowing in dry periods.
Wetlands trap suspended sediments and nutrients, and may
convert up to 90% of nitrogen in runoff to nitrogen gas,
returning it to the atmosphere, and thus preventing eutrophication of downstream water bodies. Wetlands may also be
effectively designed and managed to treat wastewaters.
In many areas there is value in maintaining and restoring
wetlands. The first step in protecting wetlands is to ensure
that adjacent drainage is not going to lower the water table of
the wetland. This may mean a weir or high-level culvert is
needed to control the water level. To protect wetland vegetation and prevent damage to ground surfaces and wetland
margins, it is preferable to prevent stock (especially cattle)
access. However, in some instances light grazing by sheep
can be effective for weed control. Replanting areas with
suitable native wetland plants can increase the rate of
recovery. A number of nurseries provide a range of suitable
plant material and excellent advice on what would be suitable for a particular site. Until wetland plants have achieved
canopy closure, ongoing weed control is likely to be needed
to prevent invasive weeds including privet and blackberry,
among others, from taking over.
Further Reading
Adcock I (1973) A goodley heritage. Eketahuna and districts 100 years
1873–1973. Eketahuna Borough and County Councils. 354 p
Ausseil A-G, Gerbeaux P, Chadderton WL et al (2008) Wetland
ecosystems of national importance for biodiversity: criteria, methods and candidate list of nationally important inland wetlands.
Landcare Research Contract Report LC0708/158 for the Department of Conservation, 162 p
Ausseil A-GE, Chadderton WL, Stephens RTT et al (2011) Applying
systematic conservation planning principles to palustrine and inland
saline wetlands of New Zealand. Freshw Biol 56(1):142–161
Belliss S, Shepherd J, Newsome P et al (2017) An analysis of wetland
loss between 2001/02 and 2015/16. Landcare Research Contract
Report LC2798 for the Ministry for the Environment, 37p. Birkeland PW (1999) Soils and gneomorphology, 3rd ed. Oxford Univ.
Press, New York, 429 p
Bouma J (1983) Hydrology and genesis of soils with aquic moisture
regimes. In: Wilding LP, Smeck NE, Hall GF (eds) Pedogenesis and
Soil Taxonomy: I. Concepts and interactions. Dev Soil Sci 11:253–
281
Childs CW (1981) Field tests for ferrous iron and ferric-organic
complexes (on exchange sites or in water-soluble forms) in soils.
Aust J Soil Res 19:175–180
Childs CW (1992) Ferrihydrite: a review of structure, properties and
occurrence in relation to soils. Zeitschrift für Pflanzenernährung und
Bodenkunde 155:441–448
Childs CW, Palmer RWP, Ross CW (1990) Thick iron oxide pans in
soils of Taranaki, New Zealand. Aust J Soil Res 28:245–257
Churchman GJ, Lowe DJ (2012) Alteration, formation, and occurrence
of minerals in soils. In: Huang PM, Li Y, Sumner ME (eds) Handbook of soil sciences, 2nd edn. Vol. 1: Properties and Processes.
CRC Press, Boca Raton, pp 20.1–20.72
Clarkson BR, Ausseil AE, Gerbeaux P (2013) Wetland ecosystem
services. In: Dymond K (ed) Ecosystem services in New Zealand—
conditions and trends. Manaaki Whenua Press, Lincoln, pp 192–
202
Cowie JD (1978) Soils and agriculture of Kairanga County. NZ DSIR
Soil Bureau Bulletin 33. 92 p
Dent DL (1978) Saline gley soils and acid sulphate soils. In: Soil
groups of New Zealand Part 3 gley soils. New Zealand Society of
Soil Science. 127 p
Fitzpatrick RW, Taylor RM, Schwertmann U et al (1985) Occurrence
and properties of lepidocrocite in some soils of New Zealand, South
Africa and Australia. Aust J Soil Res 23:543–567
Gibbs M (2007) Best practices environmental guidelines—land
drainage. Environment Waikato. 33p. ISSN:1772-4005
Hewitt AE (1993) Methods and rationale of the New Zealand Soil
Classification. Landcare Research Science Series No. 2. Manaaki
Whenua Press, Lincoln, New Zealand. 71 p
84
5 Gley Soils