Origin of Paddy Fields and Functions for Environmental Remediation in the Urbanized Areas of Yangtze River Delta - Environmental Contamination: Health Risks and Ecological Restoration - page 402

TABLE 18.2
Comparison.of.Soil.Carbon.Density.in.a.Long-Term.Field.
Experiment.of.25.Years.Conducted.in.Paddy.Soils.
Derived.from.Red.Soil.(Yintang,.Jiangxi.China,.
1981-2006)

Type Treatments 0-25cm % 0-50cm %

Upland.soil CK 3009 4059

Paddy.soil CK 4983 65.6 8345 105.6

Upland.soil NPK 2928 4278

Paddy.soil NPK 5312 81.4 8424 96.9

SOC.distribution.in.the.proiles.of.the.paddy.soil.chronosequence.(50-1000.
years).showed.that.as.the.number.of.years.of.cultivation.increased.so.did.
the.reserved.organic.carbon.in.the.deeper.layers.(Ci.et.al..2007).
Table. 18.2. shows. the. results. from. a. long-term. ield. experiment. stretch-
ing.over.25.years,.which.indicates.that.paddy.soils.derived.from.red.earth.
appear.to.have.higher.organic.carbon.stocks.and.carbon.sequestration.than.
upland. red. soils.. This. also. seemed. to. be. true. even. for. buried. prehistoric.
paddy. soils. when. compared. with. prehistoric. nonpaddy. soils. (Cao. et. al..
2006,.2007,.Lu.et.al..2006)..Paddy.soils.can.sequestrate.more.C.than.upland.
soils,.resulting.in.a.much.larger.C.sink,.with.greater.beneits.in.coping.with.
the.present.threats.of.global.warming.and.climate.change..Management.of.
increased. SOC. content,. protection. of. rice. paddy. ields,. and. utilization. of.
these. ields'. ecological. functions. may. contribute. as. vital. steps. needed. in.
achieving. CO 2 . emission. reductions. and. help. with. China's. environmental.
diplomacy.

Mutual Contention between Methane and NO 2 Emissions
The.growing.of.rice.has.traditionally.been.associated.with.adverse.environ-
mental.impacts.because.of.the.large.quantities.of.methane.gas.it.generates..It.
was.estimated.by.IPCC-EF,.from.1999.to.2000,.that.the.annual.average.meth-
ane. production. from. Chinese. paddy.ields. was. 8.19.Tg. CH 4 . per. year.. This.
level.of.greenhouse.gas.generation.is.a.large.component.of.the.global.warm-
ing.threat;.however,.this.estimation.was.based.on.data.from.winter-looded.
paddy. ields,. which. only. occupied. 10%-12%. of. the. total. Chinese. paddy.
area..Our.studies.have.demonstrated.that.methane.emissions.can.be.signii-
cantly.reduced.by.two.practices,.which.also.boost.crop.yield:.(1).draining.
the.paddies.allowing.for.the.soil.to.aerate,.and.(2).implementing.drainage.
for.the.upland.crops.during.the.whole.winter.season,.which.in.turn.inter-
rupts.methane.production.(Burton.2003,.Cai.et.al..2000,.2003,.Xu.et.al..2003)..
Chinese.farmers.have.traditional.management.practices.for.paddy.soil.such.
as.“Kao.Tian,”.which.involves.the.paddy.ields.being.drained.once.or.twice,.