Deutscher Tropentag, October 8 - 10, 2003 in Göttingen "Technological and Institutional Innovations for Sustainable Rural Development"

Effects of Manure Quality and Application Forms on Soil C and N Turnover in a Subtropical Mountain Oasis – A Laboratory Simulation of Agricultural Practices

¹University of Kassel, Department of Soil Biology and Plant Nutrition, Germany
²University of Kassel, Institute of Crop Science, Germany

Abstract

Our knowledge of the agricultural sustainability of the millennia old mountain oasis in northern Oman is restricted in particular with respect to C and N turnover. For this reason, a laboratory study was conducted to analyse the effects of rewetting and drying on microbial biomass and activity after adding organic fertilisers, to investigate the effects of a local practice where organic fertilisers are initially mulched and later incorporated into the soil, and to evaluate the relationships between C and N mineralisation rates and quality indices for different age types of manure. During the first 9 d "mulch" period, the content of extractable organic C decreased by approximately 40% in all 4 treatments. During the second 9 d "incorporation" period, this fraction decreased insignificantly in the NIL and old manure treatment and by a further 10% in the young manure and faeces treatment. The NIL and the old manure treatment form the first pair with a low percentage (0.3% in 18 d) of organic C evolved as CO₂ and a considerable percentage of total N mineralised as NH₄ and NO₃ (1% in 18 d), the young manure and faeces treatment form the second pair with a high amount (0.5% in 18 d) of organic C evolved as CO₂ and no net N mineralisation. During the first 9 d period, the microbial biomass C content increased by approximately 150% in all 4 treatments. During the second 9 d period after incorporation of the organic fertilisers, no further increase was observed in the NIL and young manure treatments and a roughly 30% increase in the other two treatments.

Keywords: CO₂ evolution, drying and rewetting, microbial biomass, N-mineralisation, substrate quality

Contact Address: Rainer Georg Joergensen, University of Kassel, Department of Soil Biology and Plant Nutrition, Nordbahnhofstraße 1a, 37213 Witzenhausen, Germany, e-mail: joergewiz.uni-kassel.de