Spring 2013Mid TestM.Nadeem Ashraf M.sc (Hons) Soil Science UAF email@example.comSalt affected and Waterlogged soils SES-706Q1. Write down the equation to calculate the pHc of water and explain its components?pHc = pk’2_pk’c+p(Ca+Mg)+p(CO3+HCO3) where thepHc= expected water pH at equilibrium with free CaCO3 in soil.Pk’2= Negative log of second dissociation constant of H2CO3 corrected for ionic strength.Pk’c= Negative log of solubility product constant of CaCO3 corrected for ionic strength.P (ca+Mg) = Negative log of (Ca+Mg, mmolcL-1) in irrigation water.P (CO3+HCO3) = Negative log of (CO3+HCO3, mmolcL-1) in irrigation water.Q2. Elaborate the treatment options for water having high RSC? Dilution: mixing with low CO3+HCO3 or high Ca+Mg Increase Ca+Mg: by application of Ca-salt, Neutralize CO3+HCO3: acid or acid forming substances-H2SO4, HCl, S etc. Gypsum being cheapest and popular amendment Practice not economicalQ3. What is the agriculture significance of Gapon equation?If we know the SAR of irrigation water then we can guess in how much time our soil become sodicdue to application of that water. SAR calculation is easy to this.Q3. Which season is better to initiate the reclamation of SAS in Punjab and why?Monsoon season is better for reclamation of SAS because good quality surplus water is available.High temperature to dissolute the lime for Na-Ca exchange etc.Q4. Enlist the parameters considered important for the classification of SAS according to SSP?SSP followed the U.S Salinity Lab. Staff followed the limits of pH, EC, SAR additionally Soil Surveyincluded some physical, morphological and land form features of soils.Q5. Enlist the factors affecting solubility of soil applied gypsum? The activity of Ca2+in solution, which in turn is governed by the solubility of solid CaSO4 insoils The size of the gypsum particles, which affects its specific surface area and thus contact withwater The rate of Ca2+diffusion from solution to exchange sites Electrolyte CEC
Spring 2013Mid TestM.Nadeem Ashraf M.sc (Hons) Soil Science UAF firstname.lastname@example.orgQ6. Why SCARPs project failed in Pakistan? Explaina) Under achievement of ambitious targetsb) Inefficient centralized management resulting in technical, operational and maintenanceproblemsc) A significant and unsustainable financial burden on scarce public resourcesd) Questionable economic performance for tube wells located in useable groundwater arease) Pumping of saline sodic water by deep tube wells of 3-5 cusec capacityf) Inappropriate mixing ratio of saline/sodic tube wells water with canal waterQ7. How plant growth is affected under sodic condition?a) Poor water and air permeability due to soil dispersionb) Low water availability due to poor air conductancec) Hindrance for seedling emergence due to hard crust on soil surfaced) Difficult seedbed preparatione) Sodium toxicity and induced potassium and calcium deficiencyf) Low activity of useful microbes due to high soil pH and SARQ8. Prove that GR (cmol c kg-1) = 2GR (mmolc L-1)GR (cmol c kg-1) = GR (mmolc L-1) x 100 x 1001000 x (5) wt. of soilGR (cmol c kg-1) = 2GR (mmolc L-1)Q9. Enlist amendments for amelioration of calcareous soil affected soils?Direct source of calciumGypsum; Calcium chloride; Calcium nitrate; Lime; Phospho-gypsumIndirect source of calciumCommercial sulphuric acid; Crude sulphur; ferrous sulphate; Aluminium sulphate; Calcium polysulphideOrganic amendmentsFYM; GM; Press mudQ10. What factors are responsible for the formation of salt affected soils in Punjab?1. arid and semiarid climate2. irrigation with low quality water3. raw city effluent disposal into irrigation water4. nearness to sea5. lack of land levelling-patchy salinity6. extra crop coverage with same water allocation7. poor apprehension of water quality guidelines8. unscientific management practices9. poor management skill of farmers10. illiterate farmers11. absentee landlordism
Spring 2013Mid TestM.Nadeem Ashraf M.sc (Hons) Soil Science UAF email@example.comQ11. Why SAR increase with the application of irrigation water? OrSAR higher of soil solution than irrigation water? Mineral weathering 70-80% ground water is Salt affected Exchange phenomenon Dissolution of sparingly soluble saltsQ12. Why gypsum is better than acid for the reclamation of saline-sodic soils?Addition of acid deteriorates the soil structure and pH fluctuation, but gypsum is gradual soluble,easy to handle, cheap source, direct source of calcium etc.Q13. Comment on the statement: Conditions that maximize P solubility are, unfortunately, thosethat destroy the soil structure?Conditions that maximize P solubility are high Na+, low EC and low pH but these can destroy the soilstructure as well.Q13. What cultural practices pertaining to water favour crop yields for management of SAS? Choice of crops and cropping pattern Seed placement Methods of raising crops Methods of water application Frequency of irrigation Age of nursery Use of mulches Root-stock scion relationship Drainage Continuous croppingQ14. Write down the important considerations to economize the reclamation of saline-sodic andsodic soils?a) Ca2++Mg2+from irrigation water could be subtracted from GR.b) If soil saturation extract contains Ca2++Mg2+subtract it from experimentally determined GR.c) While deciding final ESP, consider the tolerance for the ESP of the designed cropsd) CEC of soil should consider for the Na-Ca exchangee) Additional gypsum required to sustain electrolyte concentration in soil solution for betterinfiltration of soil in sub-humid to semi-arid regions.f) Application of gypsum rate could be reduced e.g. if 10 tons/acre of FYM are addedg) Prevailing atmospheric temperatures should be considered.
Spring 2013Mid TestM.Nadeem Ashraf M.sc (Hons) Soil Science UAF firstname.lastname@example.orgQ15. Write down the process involved during biological reclamation of salt affected soils?The biological reclamation includes organic amendments:The organic manure undergoes biochemical oxidation that release plant food, nutrients, CO2, varietyof organic acids-formation of H2CO3.H2CO3 + CaCO3 Ca (HCO3)2CO2 and organic acid dissolve the soil lime and release the soluble Ca2+to affect the Na+ desorption.Q16. How saline soils provide the parent material for the development of sodic soils?ORExplain sodication is followed by salination many times?In saline soils CaCO3 precipitate first upon the concentration of soil solution because of its lowsolubility followed by CaSO4 and magnesium silicate then there will be decrease in EC increase SARand ESP.Repitions of this process leads to the formation of saline-sodic and sodic soils.Why SAR of soil solution is higher than that of applied water?SAR depends upon the salt concentration of soil solution; the salt concentration will be more in soil.Mineral weathering and native sparingly soluble salts.Q17. Why powdery material in winter and crusty in summer on soil surface deposit?In winter due to less rainfall and low temperature water on the soil surface that evaporates, while insummer water few millimetres below the soil surface starts to evaporate due to high temperature.Q18. Explain SAR increases or decreases by square root times of dilution or concentration factor.(Principle of dilution factor or valence dilution effect)?EC Na Ca+Mg SAR2 10 10 4.481 5 5 3.164 20 20 6.33Q19. What are the options for the productive utilization of salt affected soils?1) Leaching of saline soils2) Reclamation with organic and inorganic amendments3) Physical treatments of dense soils4) Saline agriculture_ Biological means5) Planting forage and shrubs
Spring 2013Mid TestM.Nadeem Ashraf M.sc (Hons) Soil Science UAF email@example.comQ20.What is human role of salinity or sodicity?1) Constructions of roads, buildings, dams and canals blocked the surface and sub-surfacedrainage so, it develops waterlogging which promotes salinity/sodicity2) Irrigation with saline water3) Mismanagement use of irrigation water4) Change in cropping pattern5) High cropping intensity6) Lack of knowledge7) Contaminants from agro-chemicals8) Overgrazing9) Deforestation in semi-arid climateQ21. Why the slow release of CaSO4 is beneficial?CEC of Pakistani soil is low, if all the CaSO4 is dissolute in the water then all unreacted CaSO4 is leachdown.Q22. What are the sodium hazards in soils?The presence of sodium cause deteriorates the physical conditions of soil, dispersions, swelling andde-flocculation of soils occurred.Q23. Physical method for reclamation of SAS?Physical methods of soil reclamation include deep ploughing, sub-soiling, sanding, hauling, andhorizon mixing.Q24. What are the pre-requisites for the reclamation of SAS? Good internal drainage Land levelling Supply of good quality water etc.Q25. Controls of gypsum dissolution? Size of particles Indifferent types of salts Common ion effectQ27. Discuss osmotic effect on crop yields? Lower crop yield Decrease in water absorption Salts increase the energy requirements of the plants to maintain cell turgor Physiological droughtQ28. What is “Thur tirk”?Land where salts in the root zone hampers the opening of cotton bolls.
Spring 2013Mid TestM.Nadeem Ashraf M.sc (Hons) Soil Science UAF firstname.lastname@example.orgQ29. What is “Thur Juzvi”?Saline land under cultivation having visible patches of salts to the extent of 20%.Q30. In arid soils of Punjab, the value of KG varies from…………., why?The value of KG varies from 0.01 to 0.015 (litres mmol-1)1/2for most of the arid region soils and KGvalues are affected by the surface charge density of clays and organic matter contents. As SCDincreases KG value tends to decrease and vice versa.Q31. Write down the mechanism for the formation of sodic soils? ORExplain the genesis of sodic/saline-sodic soils under arid land conditions?In arid regions evapotranspiration will be more than precipitation, in saline soils CaCO3 precipitatefirst upon the concentration of soil solution because of its low solubility followed by CaSO4 andmagnesium silicate then there will be decrease in EC increase SAR and ESP. Under such conditions apart of originally adsorbed calcium and magnesium is replaced by sodium. Repetitions of this processlead to the formation of saline-sodic and sodic soils.Q32. How moderate saline-sodic water help reclamation of sodic soils?Moderate saline-sodic water is effective during the initial reclamation of sodic soils; high salt waterdilution method is effective. Presence of lime is important because its initial reclamation it providesthe calcium source.Q33. Ion pair formation in soils affects soil solution chemistry, briefly discuss its implication? The EC of saturated solution with a high proportion of Ca2+and SO2-4 ions will under estimatethe total soluble salts. Effect of ion pair formation on EC varies with the type of dissolved salts. Formation of ion complexes becomes increasingly important as ECe increases.Q34. Explain the solubility of gypsum is increased in MgCl2 soil over that in distilled water?The greater solubility of gypsum in MgCl2 solution is not due to ionic strength but also to the factthat the Mg-sulphate ion pair is formed which increased gypsum solubility by consuming SO2-4 whichis one of the products of gypsum dissolution.Q34. Briefly explain the adverse rice and wheat growth responses of crops to sodic soil conditions?Wheat is sensitive to sodicity which in turn decrease in yield and vegetative growth, rice is termed assalt friendly crop it is tolerate to sodicity, but if Na+increases of threshold level yield may reduce.Q35. Rice crop is preferred as the first crop for the reclamation of saline-sodic soils in Punjab,explain?Rice suffers less from sodicity owing to their less Ca2+requirements. Rice is the most Na+tolerantamong cultivated crops, being little affected to ESP values of 50 if climate is suitable.
Spring 2013Mid TestM.Nadeem Ashraf M.sc (Hons) Soil Science UAF email@example.comQ36. Salt affected area is increasing in Pakistan. Explain comprehensively?The location of Pakistan is in arid and semi-arid climatic zones. Global climate change is major factorfor rainfall pattern decreasing which built salts, temperature variations, less facilities to farmer,brackish underground water, rise in the water table, small holding of lands and result of humanactivities.Q37. Why salt affected soils require more application of fertilizer than normal dose?Availability of plant nutrients is affected adversely in salt affected soils: Excess of certain ions like Na, CO3 and HCO3 suppress the availability of other like Ca,K, P, Zn, Mn, Fe and B. technically, it is called antagonistic effect. An increase in soil pH, especially in sodic soils decreases the overall availability ofphosphorus and micronutrients. Nutrient uptake by plants in salt affected soils is also reduced due to decreasedwater uptake.Q38. What is the effect of salt affected soils on Nitrogen and Phosphorus availability?NITROGENAmmonium volatilization loss from applied nitrogen increases with increase in pH/alkalinity of soil.Rate of mineralization of nitrogen is slow down.PHOSPHORUSIn highly saline sodic soils about 10-15 percent more P is to be added and special care is to be takenfor calcareous soils. During reclamation of sodic soils P less because of sodic soil pH 9-10, afterwardprecipitated form of P starts to solubilize.