The Role of Soil Organic Matter and Manures in Sustainable Nutrient Cycling - Sustainable Management of Soil Organic Matter - page 243

Fig. 4.3.2. Concentrations of (a) NO 3 − and (b) DON in leachates collected from soil cores.

were larger in leachates from the cores without vegetation. Analysis of
variance using a repeated measures technique indicated that temperature
and the presence or absence of vegetation interacted to have a significant
( P < 0.01) effect on the concentration of NO 3 − in soil leachate at all time
points.
Concentrations of DON and DOC were significantly ( P < 0.001)
larger in leachates from cores with than without vegetation at all times,
whereas temperature had little effect on either DON or DOC concentra-
tions (Fig. 4.3.2b). On average, DON concentrations in leachates from
vegetated cores were over three times larger at 6.5

° C and almost five times

larger at 15 C, than those from cores without vegetation. In contrast, DOC

concentrations were twice as high in leachates from vegetated cores at both
temperatures. The average C : N ratio in leachates was significantly
( P < 0.01) greater from cores without vegetation (mean = 27) than from
cores with vegetation (mean = 19).
Over the 42-day leaching period, all the cores received 149 mg N m −2
as NH 4 + and 89.5 mg N m −2 as NO 3 − from the artificial rain. The rain
contained no DON. The flux of NH 4 + from all the cores was very small
(Table 4.3.1), whereas all the cores leached more NO 3 − than they received
in the rain (Table 4.3.1). However, when the total inorganic N input
and output fluxes are compared, it can be seen that at 6.5

°

C the cores with
vegetation received more inorganic N from the rain than they leached,
while the cores without vegetation leached 62.5 mg N m −2 more inorganic
N than they received (Table 4.3.1). At 15

°

C, both the cores with and with-
out vegetation leached a greater quantity of inorganic N, predominantly
as NO 3 − , than they received, although a larger flux was observed from
the cores without vegetation (Table 4.3.1). The difference in amount of
inorganic N leached from the cores with and without vegetation probably
represents that taken up by the vegetation, which accounted for 92.8 and
127 mg N m −2 at 6.5 and 15

°

° C, respectively (Table 4.3.1).