سنجش روند توليدنيتروژن آلي محلول در خاك هاي تيمار شده با بقاياي گياهي لگوم با استفاده از روش استنفورد و اسميت

چكيده انگليسي :

A Standford Smith Approach to Evaluate Soluble Organic Nitrogen in Residue Amended Soils Tahereh Mansouri t mansouri1987@gmail com September 12 2011 College of agriculture Isfahan University of Technology Isfahan 84156 83111 Iran Degree M Sc Language Farsi Farshid Nourbakhsh farshid@cc iut ac irAbstract Most parts of Iran are located in the arid to semi arid region of the world Therefore lack ofadequate water resulted in shortage of vegetation This has resulted in low amounts of plant residuesincorporated into the soil and hence low soil organic matter content Nitrogen deficiency is predominantlyobserved in the arid to semi arid regions of the world because N is mostly concentrated in soil organicmatter Nitrogen deficiency on the other hand is one of the most important limiting factors inagroecosystems and therefore legumes may play a key role in fixation and incorporation of N into soiland food chains This is why legumes are recognized as an effective ecosystem component which mayprovide the soil food web with N and therefore can contribute to soil fertility improvement Legumeresidues can potentially be considered as sources of soil N The Nitrogen content of the plant residues aremostly in organic forms Some of the organic forms of N can be dissolved in the soil water followed byincorporation in the soil Soluble or insoluble forms of organic N are subjected to the N mineralizationswhich take place by the heterotrophic soil population The objective of this study was to investigate theeffects of legume residue application on the release of soluble inorganic and organic N in soil For thispurpose two soil types were collected from 0 15 cm of Shervedan and Chelvan The residues ofsainfoin Onobrychis viciifolia clover Trifolium repens and alfalfa Medicago sativa L were driedpaassed through 1 mm sieve and kept in the refrigerator The plant residues were applied to the soils atthe rate of 10 g kg 1 soil control treatments without application of the plant residues were alsoconsidered for both soils Stanford and Smith leaching columns were prepared for both residue appliedand control soils with three replications The soils were kept in incubator for 20 weeks and the releasedinorganic and organic N was measured at different time intervals Results indicated that application of theplant residues has resulted in soluble organic and inorganic N Expectedly the release of inorganic N wasconformed to an exponential first order kinetic model In contrast none of the treatments showedexponential increasing trend in the soluble organic N In all of the time intervals alfalfa residues broughtabout greater amounts of inorganic N The lowest amount of inorganic N was observed in the clover applied soils The potentially mineralizable N was lowest in the control soils The amount of Nmineralized at the end of incubation was significantly correlated with the potentially mineralizable N r 0 6 P 0 001 and initial potential rates of N mineralization r 0 9 P 0 001 The soluble organic N wasincreasingly increased by time In the Shervedan soil the soluble organic N was equal among thetreatments while in the Chelvan alfalfa treated soils possessed the lowest amounts of soluble organic N In both soils the final concentrations of soluble organic and inorganic N were negatively associated Inthe Shervedan soil r 0 63 P 0 05 and in the Chelvan r 0 6 P 0 05 Moreover the soluble organic Nwas also negatively correlated with initial potential rates of N mineralization In the Shervedan soil r 0 58 P 0 05 and in the Chelvan r 0 65 P 0 05 Key words Soluble Organic Nitrogen N mieralization Sainfoin Clover Alfalfa Incubation leaching Standford Smith method

منصوري، طاهره

سنجش روند توليدنيتروژن آلي محلول در خاك هاي تيمار شده با بقاياي گياهي لگوم با استفاده از روش استنفورد و اسميت

گياه شبدر , گياه اسپرس , آبشويي-انكوباسيون