title: The effect of soil temperature and moisture on organic matter decomposition and plant growth.
abstract: The effect of soil temperature and moisture on plant growth and mineralisation of organic residues was investigated using 15N-labelled soybean residues and temperature-controlled tanks in the glasshouse. Treatments were arranged in a factorial design with: three soil temperatures (20, 26 and 30 degrees C), two soil moisture regimes (8% (-800 Kpa) or 12% (-100 Kpa)), soybean residues added (enriched at 1.82 atom % 15N excess) or no residues; and either sown with ryegrass or not sown. Pots were sampled six weeks after planting and 15N-enrichment and delta13C of the plant and soil fractions were determined. Soil inorganic N was also periodically measured. Available inorganic N increased significantly with addition of residues and generally decreased with increasing temperature. Plant dry matter decreased significantly with increase in soil temperature and increased with increasing moisture. Root-to-shoot ratio declined with increased temperature and moisture. Percentage nitrogen derived from residues (%Ndfr) increased linearly with increased temperature and moisture. Delta13C decreased linearly with increasing temperature and decreasing moisture status. There was a significant correlation between transpiration and dry matter production, but there was no correlation between water use efficiency and delta13C. The results suggest that C: N ratio of the root material effects the root turnover and in turn the water supply capacity of the root system.
authors.affiliation: Soil Science Unit, FAO/IAEA Agriculture and Biotechnology Laboratory, Seibersdorf, Austria. r.hood@iaea.org
authors.forename: R C
authors.initials: RC
authors.lastname: Hood
mesh_terms: D001317:Austria; D002247:Carbon Isotopes; D017753:Ecosystem; D009587:Nitrogen Isotopes; D018517:Plant Roots / Q000502:physiology; D012434:Secale / Q000254:growth & development*; D012987:Soil; D013025:Glycine max / Q000254:growth & development* / Q000502:physiology; D013696:Temperature; D014867:Water
chemical_list: D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D012987:Soil; D014867:Water