Agriculture Reference
In-Depth Information
Table 2.5.
Half-life and annual loss of seeds from soil for 20 weed species, computed
from seed survival over a five-year period
a
Loss per year (%)
Half-life (years)
Cultivated
Uncultivated
Cultivated
Uncultivated
Capsella bursa-pastoris
43
24
1.2
2.6
Chenopodium album
31
8
1.9
8.3
Euphorbia helioscopia
54
21
0.9
3.0
Fumaria officinalis
34
16
1.7
4.1
Matricaria matricarioides
33
28
1.8
2.1
Medicago lupulina
30
22
2.0
2.8
Papaver rhoeas
38
30
1.4
2.0
Poa annua
26
22
2.3
2.8
Polygonum aviculare
47
16
1.1
4.0
Polygonum convolvulus
50
25
1.0
2.4
Senecio vulgaris
b
45
b
1.2
Spergula arvensis
60
30
0.8
2.0
Stellaria media
54
32
0.9
1.8
Thlaspi arvense
50
10
1.0
6.8
Tripleurospermum maritimum
ssp.
inodorum
36
23
1.6
2.6
Urtica urens
37
17
1.5
3.7
Veronica hederifolia
b
13
b
5.1
Veronica persica
54
22
0.9
2.8
Vicia hirsuta
36
30
1.6
2.0
Viola arvensis
40
15
1.4
4.2
Notes:
a
Seeds were mixed with the top 15 cm ofsoil and either left undisturbed or mixed four times
per year.
b
No seeds viable after five years.
Source:
From Roberts & Feast (1972).
seed survival (Villiers, 1973), whereas seed longevity is much less in agricultu-
ral fields (Table 2.5). Often the logarithm of seed density plotted against time
follows a straight line for weed seed banks (Roberts & Dawkins, 1967; Roberts
& Feast, 1973), although in some cases the mortality rate is somewhat higher
or lower during the first year (Figure 2.3). Thus, seed survival times are often
better characterized by the half-life of the population rather than the
maximum age achieved by the most persistent individual. Studies on weed
seed survival lead to two general conclusions. First, a substantial portion of
the seeds of even relatively persistent species disappears from the soil each
year, and second, soil disturbance increases the rate of disappearance (Table
2.5) (Roberts & Feast, 1972; Lueschen & Andersen, 1980; Froud-Williams,
Chancellor & Drennan, 1984; Warnes & Andersen, 1984; Barralis, Chadoeuf &
Lonchamp, 1988).
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