European Journal of Agronomy 14 2001 61 – 74
The use of hedges to reduce winter wheat losses caused by Italian ryegrass Lolium multiflorum
M.A. Martı´nez-Ghersa
a,
, C.M. Ghersa
a
, S.R. Radosevich
b
, D.O. Ferraro
a
a
IFEVA, Department of Natural Resources and En6ironment, Faculty of Agronomy, Uni6ersity of Buenos Aires, A6. San Martı´n
4453
, Buenos Aires
1417
, Argentina
b
Department of Crop and Soil Science, Oregon State Uni6ersity, Cor6allis, OR
97331
, USA Received 22 February 2000; accepted 9 August 2000
Abstract
We hypothesized that short duration plant interference aiming to change mainly light intensity and red:far red ratio during crop establishment in Italian ryegrass-infested winter wheat fields, could hinder the development of Italian
ryegrass and thus reduce its effect on wheat yield. To test this hypothesis, wheat was planted between previously established live low red:far red ratio or dead high red:far red ratio, barnyardgrass or maize, plant hedges.
Experimental results demonstrated that the presence of live or dead plant hedges during the first 30 days of crop establishment and also hedge orientation were important factors regulating weed and crop biomass production and
competitive relationships. In barnyardgrass hedge treatments wheat yield was improved up to 67 and Italian ryegrass production was reduced by more than 20. In plots with maize live hedges oriented N – S the biomass
production of wheat was independent of production of Italian ryegrass. Data presented here suggests that there is room for developing weed control technologies on the basis of understanding photosensory processes of weed and
crop species. © 2001 Elsevier Science B.V. All rights reserved.
Keywords
:
Weeds; Competition; Light; Redfar red ratio; Yield www.elsevier.comlocateeja
1. Introduction
Tactics to reduce the negative effects of weeds on crop performance generally include the use of
herbicides and soil tillage Aldrich, 1984; Altieri, 1988; Navas, 1991; Tivy, 1990. Herbicide use has
allowed agriculture to keep pace with human population growth Altieri and Liebman, 1988.
However, the increased emphasis on herbicide use has sometimes resulted in fewer crop rotations
and caused alternative techniques of weed control to be abandoned, which leads to even more inten-
sive herbicide use. This intensive use selects for resistance in some plant species and generates
concerns about contamination of ground water and human toxicity Gressel, 1991.
Many symposia, review papers and texts Ra- dosevich et al., 1997 stress the importance of
Corresponding author. Fax: + 1-541-7371393. E-mail address
:
ghersamucs.orst.edu M.A. Martı´nez- Ghersa.
1161-030101 - see front matter © 2001 Elsevier Science B.V. All rights reserved. PII: S 1 1 6 1 - 0 3 0 1 0 0 0 0 0 8 5 - X
research in weed biology to develop information on new cultural methods of weed management.
Yet few researchers demonstrate how weed biol- ogy actually can be used to improve weed control
Holt, 1995; Radosevich et al., 1997. Recent re- search suggests that manipulation of the light
environment near the soil surface could be an additional weed management strategy in cropping
systems Ballare´ et al., 1987; Ballare´, 1993; Ballare´ et al., 1992; Benech Arnold et al., 1990; Ghersa et
al., 1994. This strategy requires identification of differences in crop and weed response to environ-
mental signals. With such information, light envi- ronments
can be
created that
deliver the
appropriate signals to promote crop performance andor inhibit weed species.
Crops and weed species generally differ in their response to changes in environmental signals be-
cause plant breeding tends to reduce architectural plasticity of crops Patterson, 1985. For example,
Italian ryegrass Lolium multiflorum is a weed in
Fig. 2. Layout of experimental plots for studying the effect of orientation and spacing of live and dead maize hedges on
wheat and Italian ryegrass relative performance see text for details. General plot layout showing the two hedge row
orientations N – S and E – W and the demarcation of areas containing sprayed brown and nonsprayed green hedges
A, maize hedge spacings used in the study and placement of the biomass sampling plots within the hedge spacings B.
Fig. 1. Layout of experimental plots for studying the effect of short-term shading with barnyardgrass hedges on wheat and
Italian ryegrass biomass production in high-and low-density Italian ryegrass plots.
winter cereals. Its seed has a longer dormancy period than wheat seed, and biomass production
is more responsive to changing soil and light environments than wheat. Ghersa et al. 1994
were able to significantly lower Italian ryegrass dry matter and seed production, and improve
wheat yield by reducing both light intensity and red to far red R:FR ratio near the soil surface
during winter wheat establishment.
Table 1 Percentage Italian ryegrass plant cover relative to total plant cover for each plot type, measured 141 days after wheat sowing
a
Pure I. Ryegrass Barnyardgrass
Mixed wheat-I. Ryegrass Hedges
Low density High density
High density Low density
Total Relative
Total Relative
Relative Total
Relative Total
Yes 100.0
11.8 100.0
0.8 15.7
44.0 4.2
37.9 No
100.0 31.2
100.0 3.5
46.3 39.6
33.8 33.0
a
Within each column of values, denotes a significant PB0.05 difference between barnyardgrass and non-barnyardgrass plot means.
In this study, we tested the hypothesis that manipulating some agronomic variables, aiming
to produce changes especially in the light environ- ment during early stages of the crop, can improve
wheat ability to compete with ryegrass. Live and dead hedges grown with summer annuals barn-
yardgrass and maize, separated by various dis- tances, were used to reduce the ground-level light
intensity and alter the R:FR ratio during winter wheat seedling establishment in Italian ryegrass
infested plots.
2. Materials and methods
