The Role of Soil Organic Matter and Manures in Sustainable Nutrient Cycling - Sustainable Management of Soil Organic Matter - page 242

Soil incubation experiment

Net mineralization occurred at all temperatures, with larger rates observed
at higher temperatures (Fig. 4.3.1a); the average daily rates were 6.7, 25.3
and 62.7 mg N m −2 day −1

C, respectively. In contrast,
water-extractable DON displayed no clear trend over the incubation
period, although the amount extracted on day 28 was significantly
( P < 0.001) smaller than at other times, and showed little response to
temperature (Fig. 4.3.1b). Additional DON, equivalent to 2gNm −2 ,
extracted with 0.5 M K 2 SO 4 , also showed little sensitivity to changes in
time or temperature.

at 5, 10 and 15 °

Soil leachate experiment

Concentrations of NH 4 + in leachates from all the soil cores were small
(ranging typically between 0.25 and 0.5 mg N l −1 ) and varied little with
time or between each other. Concentrations of NO 3 − in leachates from
the soil cores without vegetation steadily increased over the 42 days (Fig.
4.3.2a), and the rate of increase was greater for the cores at 15

° C than at

6.5 C. In contrast, concentrations of NO 3 − in leachates from the soil cores

with vegetation initially increased before decreasing after day 10 at 15

°

° C

and after day 21 at 6.5 C (Fig. 4.3.2a). Concentrations, however, were

consistently larger in leachates from the cores at 15

°

° C than at 6.5 ° C. At

15 C, concentrations of NO 3 − initially were larger in leachates from cores

with vegetation than without, until after day 12 when concentrations of
NO 3 − were larger in leachates from cores without vegetation (Fig. 4.3.2a).
At 6.5

°

C, there was little difference in the concentration of NO 3 − between
cores with or without vegetation until after day 21, when concentrations

°

Fig. 4.3.1. Changes in (a) 0.5 M K 2 SO 4 -extractable inorganic N and (b) water-extractable DON
during incubation of a peaty podzol at 5, 10 and 15 ° C.