Incubation

About: Incubation is a research topic. Over the lifetime, 5748 publications have been published within this topic receiving 126541 citations.

Soil drying and rewetting and the turnover of 14C-labelled plant residues: First order decay rates of biomass and non-biomass 14C

Abstract: The effects of drying and rewetting on soil organic C derived from added plant material were determined. Three soils, one silty-loam and two loamy sands, were incubated with 14C-labelled plant material for 27 days. Each soil was then subjected (1) to drying at 40°C for 3 days, remoistening and incubation at 25°C for 10 days, and (2) to storage at 4 °C for 3 days and incubation. The silty-loam soil was also treated after 7 days of incubation with 14C-labelled plant material. Residual 14C concentrations were determined at the beginning and at the end of the 10 day incubation. During drying or storage and subsequent incubation of soils, biomass C and 14C were measured, and also the amounts of CO2 and 14CO2 released during the 10 day incubation. Residual 14C concentrations at the end of the incubation were not significantly affected by soil desiccation and remoistening, but the percentages of residual 14C due to biomass 14C were greatly reduced in dried, rewetted and incubated soils. The effect was largest for the soil which had been incubated for the shortest time with 14C-labelled plant material. Average first-order gross decay rates were calculated for biomass 14C and non-biomass 14C, and for different efficiencies of substrate utilization (viz. 20, 40 and 60%). Two time intervals were chosen: with and without inclusion of the drying period. Drying and rewetting of soils enhanced first-order gross decay rates of the two carbon pools. The relative increases were larger for decay rates of biomass 14C than for those of non-biomass 14C. When decay rates were averaged over a time interval that did not include the drying period, observed effects of soil desiccation and remoistening were less pronounced, but still apparent. This suggests that a previous drying-rewetting cycle has an appreciable influence on decomposition processes during later incubation of soils. It was concluded that soil drying and rewetting promoted the turnover of C derived from added plant material, and that this increase in C cycling was mainly due to enhanced turnover of microbial products. This may finally result in a change of quality of the organic C pool coming from added plant residues.

Soil nitrogen mineralization during laboratory incubation: Dynamics and model fitting

Abstract: Soil nitrogen mineralization kinetics were studied for eight treatments of two soils in an aerobic long-term (30 wk) incubation experiment. Soil mineral-N (NH 4 + and NO 3 − ) in the leachates was measured every week during the first 9 wk and every 2 or 3 wk thereafter. The NH 4 + percentage of the mineral-N ranged between 85 and 99% for all treatments in the first week of incubation and remained high (> 80%) in several treatments until the end of wk 4. Starting at wk 7, NH 4 + concentrations were negligible in all treatments. The net N mineralization rate was 15–24 mg N kg −1 wk −1 during the first 4–6 wk and 2–5 mg N kg −1 wk −1 from wk 8 until the end of the incubation. Four models, (i) a one-component, first-order exponential model (the single model), (ii) a two-component, first-order exponential model (the double model), (iii) a one-component, first-order exponential model including a constant term (the special model), and (iv) a hyperbolic model, were fit to the cumulative mineral-N vs time data using a non-linear regression procedure. The goodness of fit of the four models depended on the duration of incubation. With 30 wk data, the double and special models were significantly better than the other two models; with the first 15 wk data, the four models had essentially the same goodness of fit for seven out of eight treatments. The values of the regression parameters derived from each model also depended on the incubation duration. Results from this study show that the pool size and mineralization rate parameters in the different models are merely mathematically-defined quantities obtained from the kinetic analysis of the net N mineralization and do not represent any rigorously-defined pool sizes of potentially-mineralizable N and their mineralization rate constants in the soils.