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All issues Volume 30 / No 2 (April-June 2010) Agron. Sustain. Dev., 30 2 (2010) 445-453 Full HTML
Open Access

Table I

Weed abundancea in full plots and subplotsb of the long-term Beltsville Farming Systems Project.

Year Systemc Weed coverd Weed biomass Pigweed+Lambsquarterse
(%) (g m−2) (%)
Full plot Subplot Subplot Full plot Subplot
1997 NT 17 b 20 a 64 b 43 b 62 b
Org2 50 a 55 a 262 a 100 a 100 a
Org3 23 b 29 a 71 b 83 a 63 b
Org4f - - - - -
1998 NT 15 c fwg fw 16 c fw
Org2 65 a 54 a - 99 a 100 a
Org3 29 b 38 a - 100 a 99 a
Org4 32 b 34 a - 53 b 64 b
2001 NT 50 b 58 a 137 b 20 c 10 d
Org2 68 a 61 a 254 a 88 a 99 a
Org3 53 ab 49 a 101 b 25 c 40 c
Org4 28 c 38 a 68 b 57 b 68 b
2002 NT 3 b fw fw 56 c fw
Org2 84 a 69 a 387 a 88 a 91 a
Org3 - - - - -
Org4 75 a 84 a 238 b 100 a 100 a
2004 NT 5 b fw fw 37 b fw
Org2 35 a 58 a 182 a 94 a 94 a
Org3 14 b 15 b 44 b 81 a 85 a
Org4 3 b fw fw 73 a fw
2005 NT 1 b fw fw 6 b fw
Org2 37 a 48 a 228 a 94 a 97 a
Org3 10 b 22 a 117 a 91 a 97 a
Org4 3 b fw fw 89 a fw
a

Values followed by the same letter within a column and year are not significantly different at P < 0.05.

b

“Full plot” refers to plots 12 rows (9.1 m) by 111 m long from which weed data were taken from the middle 6 rows. “Subplot” refers to a 4 row (3.0 m) by 6.1 m long area within a full plot from which weed data were taken from the middle 2 rows.

c

NT = conventional no-tillage system, Org2 = two-year corn-soybean organic rotation, Org3 = three-year corn-soybean-wheat organic rotation, Org4 = four-year corn-soybean-wheat-hay organic rotation.

d

Percent of soil area covered by weed vegetation.

e

Percent of weed vegetation composed of smooth pigweed and common lambsquarters.

f

There was no corn that followed two years of hay in this startup phase of the project.

g

Subplots were not established in systems where there was low weed abundance at the time of subplot establishment (fw = few weeds).