Microbial activity and biomass and N and P availability in a saline sandy loam amended with inorganic N and lupin residues
Date
2011
Authors
Elgharably, A.
Marschner, P.
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Journal article
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European Journal of Soil Biology, 2011; 47(5):310-315
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Ahmed Elgharably, Petra Marschner
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Abstract
Plant residue can be a cost effective source of N and P fertilisers, which may enhance plant growth in saline soils. Salinity and limited availability of N may limit microbial activity and thus residue decomposition N and P availability. A laboratory experiment was conducted to investigate the effects of NH<inf>4</inf>-N or NO<inf>3</inf>-N on microbial activity and biomass and N and P availability in a saline sandy loam. Three levels of salinity (EC<inf>1:5</inf> 0.21, 0.51 and 0.85 dS m<sup>-1</sup>) were imposed in the sandy loam using solutions of Na<sup>+</sup> and Ca<sup>2+</sup>. Soil was amended with or without 2% (w/w) lupin residues (C/N ratio 15.4) or 50 μg N g<sup>-1</sup> soil as KNO<inf>3</inf> or (NH<inf>4</inf>)<inf>2</inf>.SO<inf>4</inf>. With no residue or inorganic N added, the concentration of available N and P remained unchanged over 45 days. Soil respiration and microbial biomass C, N and P decreased with increasing salinity, but significantly increased with residue addition. Addition of inorganic N had no significant effect, but addition of NO<inf>3</inf>-N with residue significantly increased soil respiration and microbial biomass C, N and P. Salinity had no effect on N availability and decreased P availability. Nitrogen availability was lower with addition of NH<inf>4</inf>-N, N than with NO<inf>3</inf>-N. Available N and P increased with residue addition and increased further with addition of NO<inf>3</inf>-N than with NH<inf>4</inf>-N. The greater C availability in the lupin residue amended saline sandy loam stimulated microbial activity and biomass with greater N demand, thus promoted immobilization of NO<inf>3</inf>. Hence, N and P availability increased in the saline sandy loam. © 2011 Elsevier Masson SAS.
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Copyright © 2011 Elsevier Masson SAS. All rights reserved.