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Increasing the value of soil respiration measurements (for AU NT21) - NT1524

Previous research has shown that soil respiration is a good general indicator of mineralization. However, data also show that a more detailed understanding is required of how temperature and moisture content affect CO2 efflux. This study will increase the value of soil respiration measurements by measuring temperature and moisture content consecutively while collecting data relating to CO2 flux. The study will be composed of 3 objectives which are outlined as follows, together with ways in which they might be achieved: 1. Calibration of 12 individual thermistors and moisture content sensors for use with an automated CO2 infrared gas analysis (IRGA) system so that simultaneous measurements of temperature and moisture content may be collected alongside CO2 flux measurements. Calibration of thermistors will be performed by operating each one through its full temperature range, as measured simultaneously by mercury thermometers, and recording its resistance. Gypsum blocks will be buried in microcosms of the topsoil taken from sites and will be set up at typical dry bulk densities of tilled soil ranging from 1.1 to 1.3 kg dm-3 and saturated. Resistance of gypsum blocks will be measured at successive intervals as the microcosms drain and evaporate to dryness, and the moisture content will be measured by weight difference; 2. Measurement of temperature and soil moisture content in the surface 10 cm of soil directly adjacent to the point of, and at exactly the same time as, respiration measurement. Temperature and moisture content readings will be correlated with respiration rates taken simultaneously at 3 sites on several different occasions spanning a wide range of edaphic conditions. These data will be used for multiple regression analyses that quantify the dependence of respiration rate on these parameters; and 3. Comparison of CO2 respiration using a hand held IRGA with those obtained from an alkali absorption method over 24 hours, in order to quantify the efficiency of infrared spectroscopy over passive chemical absorption. Results of the study will produce standardised respiration rates that will better reflect underlying treatment differences and will provide more accurate measurements for validation of N mineralization models.
Time-Scale and Cost
From: 1997

To: 1998

Cost: £12,214
Contractor / Funded Organisations
Fields of Study
Fertilisers and Nitrate Pollution