1、Salt-affected Soils1.通常發生於semiarid and arid regions annual precipitation evapotranspiration2.Natural sources of soil salinity a)Mineral weathering b)Fossil salts c)Atmospheric precipitation3.Local salt accumulation Soils in low-lying areas EvaporationCapillary risewater table4.Human Activitiesa)Salt
2、s from areas of over-irrigation accumulate in poorly drained areas.a)Relatively saline irrigation water are used.a)Oil-field development,waste-spreading operation,and crop fertilization灌溉水質1.Total Dissolved Solids(TDS)大部分之灌溉用水 TDS 2.5 hazardous 1.25 RSC 2.5 potentially hazardous RSC 1.25 generally s
3、afe Empirical but worked reasonably well 22-23-3MgCa-COHCORSC223-32COOHCaCO2HCOCa Increasing SAR of water項目限值項目限值pH 值6.0 9.0鈷 (Co)mg/L0.05電導度 mho/cm 25750銅 (Cu)mg/L0.2懸浮固體物 mg/L100鉛 (Pb)mg/L0.1氯化物(Cl-)mg/L175鋰 (Li)mg/L2.5硫酸鹽(SO4-2)mg/L200錳 (Mn)mg/L2總氮量(T-N)mg/L1汞 (Hg)mg/L0.005清潔劑(ABS)mg/L5鉬 (Mo)mg/L
4、0.01油 脂 mg/L5鎳 (Ni)mg/L0.5鋁 (Al)mg/L5硒 (Se)mg/L0.02砷 (As)mg/L1釩 (V)mg/L10鈹 (Be)mg/L0.5鋅 (Zn)mg/L2硼 (B)mg/L0.75鈉吸著率(SAR)6鎘 (Cd)mg/L0.01殘餘碳酸鈉 RCS(meq/L)2.5鉻(總)(Cr)mg/L0.1水溫35表表3.1台灣省灌溉用水水質標準台灣省灌溉用水水質標準(67.7.5府建水字第府建水字第59931號公告號公告)附註：天然之水質若超過本標準之限值，得不受本標準之限制。Characterization of Salt-affected Soils 1.Na
5、-status (i)ESP(Exchangeable Sodium Percent)100CECNaX直接測定ESP費時麻煩，且常有誤差(ii)SAR(Sodium Adsorption Ratio)Soil Soln.做為 exch.-Na status 之 index1/222/2MgCaNaSARSAR KESRGESR1ESR 100ESPConc.單位：m moles(+)/LESP SAR NaX-CECNaXratio)Na(exch.ESREffects of salts on soils and plants1.Main effect on plantsOsmotic Ef
6、fectWaterSemipermeable membraneHigh salt conc.Outside the membraneHigh salt Osmotic potential 愈負 Water potential 愈負Difficult to extract water Osmotic adjustmentProduction of organic acids or update of salts使 osmotic potential愈負 water potential 愈負然而消耗energy，並發生葉組織細胞不斷之分裂但不增長之現象Possible to continuousl
7、y obtain waterWater potentialInside the membrane2.Specific-ion effects Plants are sensitive to specific ions in irrigation water or soil soln.Boron,Chloride,ESP Effect3.Nutritional imbalances e.g.bicarbonate toxicity 是由於high pH引起iron或其他micronutrients之deficiency,而不是bicarbonate直接引起之effect.Other toxic
8、Solutes B,Li,Na and Cl B(Boron)缺乏毒害 之間只相差a few mg/LLeaching Requirement(LR)dwiwiwdwECECDDLRDdw:Amount of drainage waterDiw:Amount of irrigation waterECiw:Electrical conductivity of irrigation waterECdw:Electrical conductivity of drainage water為了維持Salt balance(Salt entering=Salt leaching)所需之Leaching
9、fraction(假設no salt propitiation,no salt dissolved from soil minerals,and no salt taken up by the crop)Ddw ECdw=Diw ECiw ECdw(allowable EC of the saturation extract)can be obtained from existing salt tolerance data(Table 9.2).e.g.Soybean ECdw 5.5 ds m-1 at 25Reclamation1 Saline,non-sodic soils Leachi
10、ng ponding-inefficient basin-furrow methodReclamation2 Saline-Sodic Soils;Sodic soils a)Decrease ESP application of gypsum(CaSO4 2H2O)NaX-CaX-NaCa211/22 or tillage(深耕)bring subsoil lime to the surface 對calcareous-sodic soils 施用S4222SO2HO2H3O2S224423COOHCaSOSOHCaCO424SONaCaXCaSO2NaXb)LeachingSAR 60(H
11、igh-salt water)Soil ESP=40-50 2nd leaching with 1st fourfold dilution of the high-salt water150 m mole(+)L-1 salt conc.,SAR 303 Sodic soils High-salt water-reclamations 1st leaching with 600 m moles(+)L-1 salt conc.3rd leaching with 2nd fourfold dilution of the high-salt water37.5 m mole(+)L-1 salt conc.,SAR 154th leaching with 3rd fourfold dilution of the high-salt water9.4 m mole(+)L-1 salt conc.,SAR 7.5Problem:Drainage facilities need to be adequate to remove large quantities of salty drainage water.
