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PRIMING MECHANISM: SOIL AMENDED WITH CROP RESIDUE

S.  MUHAMMAD¹, R.G. JOERGENSEN², T. MUELLER² AND T.S. MUHAMMAD³

Abstract: Priming effect is an extra decomposition of organic C after addition of easily-decomposable organic substance to the soil. Moreover, priming effects are strong short term changes in the turnover of soil organic matter caused by comparatively moderate treatments of the soil. The priming effect arises either immediately or very shortly after the addition of a specific substance to the soil.  Priming affects in soils rich in C and N are larger than those in poor soils. The size of priming effects increases with the amount of the added organic substances or mineral fertilizers. An opinion expressed in literature says that not only microorganisms alone contribute to priming effects. Interactions between soil microorganisms, soil fauna and plants are regarded as one of the keys for understanding priming effects. Substances released by soil fauna can cause priming effects by stimulating microbial activity. However, more prevalent in the literature are descriptions of the faunal grazing on soil microflora (predation). The effects induced by predation as fallow: increased CO₂ release, increase N and P mineralization and release of nutrients immobilized in microorganisms, increased N up take of plant, and intensified plant growth ultimately. Similar trend was observed in our study regarding the nutrients mobilization which can be termed as priming effects. In this study extra mineralization of 400 µg g^-1 soil CO₂–C production resulted in priming effect of the added alfalfa residue.

¹Department of Soil and Environmental Sciences, University College of Agriculture, University of Sargodha, Sargodha, Pakistan, E-mail: shermuhammad10@hotmail.com (Tel. 0304-9507108)

²Department of Soil Biology and Plant Nutrition, Witzenhausen, University of Kassel, Germany

³Department of Chemistry, Islamabad Model College for Girls F-6/2, Islamabad, Pakistan