See more from this Session: National Student Research Symposium Poster Contest
Monday, October 17, 2011
Henry Gonzalez Convention Center, Hall C, Street Level
Labile soil carbon is the fraction of organic matter that is readily degradable (<5 years) and is therefore available as an energy source for soil microbes. Given that microbes drive soil nutrient mineralization, a measurement of active carbon could help predict the mineralization potential of soils and be used to inform fertilizer applications. Twenty-four hour basal respiration has been correlated with N and P mineralization and this method for estimating active carbon has the potential to be adopted on a large scale in commercial soil labs. The objectives of this study were to (1) investigate effects of long-term compost application on labile soil carbon at 0-10cm and 0-30 cm and (2) examine the effects of soil storage on 24-hour basal respiration. We measured 24-hour basal respiration from 3 field replicated treatments within the Long-term Organic Farming Systems Experiment at WSU Puyallup: 1) On-Farm Compost (15:1, C:N applied annually at 30 Mg ha-1 for 8 years); 2) Chicken Manure Compost (11:1, C:N, applied annually at 5 Mg ha-1 for 8 years; and 3) Low-Input Pasture (On-Farm Compost applied annually 2003-2005, currently rotated with pasture for 2 of every 3 years). For the on-farm and chicken compost treatments, 24-hour basal respiration produced a mean of 143 mg CO2 kg soil-1 wk-1. Microbial biomass, measured via substrate-induced respiration, was significantly higher in the On-Farm compost treatment. Assessing the sensitivity of 24-hr basal respiration to long-term compost treatments and the effect of soil storage on this method could affect how it is adopted in research and on a larger scale.