Gross N fluxes and microbial population dynamics after the addition of organic amendments to coarse-textured soil

[Truncated] Typically, vegetable production in Western Australia occurs on coarse-textured soils with low organic matter (OM) and clay contents and low inherent fertility. Soil OM content can be improved by the addition of organic amendments such as compost. However, for effective use of these amendments in commercial systems, a better understanding is required of factors such as carbon (C) quality and its impact on soil microbial biomass and activity levels which influence the magnitude and timing of nitrogen (N) release after amendment application. This research provides detailed information on these factors, to assist our understanding of N cycling after organic amendment application and to aid in the development of more efficient management practices for their use. A series of experiments (both laboratory and field based) were conducted to determine the impact that the addition of organic amendments had on soil C and N contents, microbial populations, gross N cycling and lettuce yield. The impact of amendment 'quality' (chemical composition and degree of composting), its rate of application and the effect of inorganic fertilizers and clay amendment in combination with compost, on these parameters were assessed.