168 D.W. Lucero et al. European Journal of Agronomy 11 1999 167–177
1. Introduction
Preference at the Ecole Nationale Superieure d’Agronomie
et des
Industries Alimentaires
White clover Trifolium repens L. is commonly ENSAIA, Nancy, France. In March of 1995
used as a perennial forage legume in the temperate seedlings were grown in specially constructed PVC
zones of both hemispheres. Usually, white clover is tubes and boxes described below. Three composi-
grown with one or more grass companions, the most tions of white clover and ryegrass plant interaction
common being perennial ryegrass Lolium perenne were combined with three levels of soil water
L. Hill and Michaelson-Yates, 1987. Grown deficit in a randomized complete block experiment
together, white clover and ryegrass are major contrib- with four replications. White clover was inoculated
utors to the productivity and quality of pastures. with Rhizobium triflii SB116 on day 10. From
In mixture, grasses and legumes compete for week four to nine a complete nutrient fertilizer
water, light and nutrients and may also compete for solution Robin et al., 1992 was applied once per
O 2
, CO 2
and space Haynes, 1980. Mixture studies week. This nutrient solution was slightly modified
have often looked at the effects of cutting and in order to supply both white clover and ryegrass
grazing Wilman and Asiegbu, 1982; Evans and with N, P, and K at rates equivalent to
Williams, 1987; Woledge et al., 1992a, inorganic N 165 kg ha−1, 60 kg ha−1 and 60 kg ha−1, respec-
and temperature Davidson and Robson, 1986; tively. Average daily maximum and minimum air
Ledgard, 1991; Nesheim and Boller, 1991 and light temperatures
were 26±4°C
and 13±3°C,
and photosynthesis Dennis and Woledge, 1985; respectively.
Thompson and Harper, 1988; Woledge et al., 1992b, as well as competition Martin and Field, 1984;
2.2. Plant interaction treatments Menchaca and Connolly, 1990; Lu¨scher et al., 1992.
The dynamics of water availability and use are White clover and ryegrass were grown as fol-
essential factors differentiating plant survival in a lows: 1 individually no interaction; 2 shoot
pasture. Little, however, is known concerning only interaction shoot interaction; and 3 both
white clover and ryegrass response to water deficit root and shoot interaction shoot+root inter-
in a mixed pasture. Reduced white clover growth action. White clover and ryegrass grown in no
in pasture mixtures under drought has been attrib- uted to its less extensive rooting system Thomas,
interaction were seeded into plastic PVC tubes 1984; Guobin and Kemp, 1992. Yet the capacity
5 cm in diameter and 30 cm in depth filled with of white clover to extract water from deep soil
soil made of a quartz sand filtered to pass a 2 cm reserves has also been reported Guckert et al.,
sieve added to a potting mix at a weight propor- 1993. Therefore, the results concerning white
tion of 70:30 and packed to simulate a bulk density clover are conflicting. This greenhouse study was
of 1.25±0.10 g cm−3. Individual PVC tubes were conducted to determine the effects of soil water
spaced at intervals of 20 cm. For shoot interaction, deficit and interspecific plant interaction on the
20 PVC tubes 10 white clover and 10 ryegrass dry matter DM yield of white clover and ryegrass
plants, identical in nature to those containing no and on the morphogenesis of white clover. White
interaction plants, were placed in a 5×4 grid in an clover and ryegrass were grown in a shallow soil,
alternative pattern in specially constructed crates either individually no interaction or in mixtures
30 cm×24 cm×30 cm. The 14 plants on the of equal numbers with just shoot interaction or
outer edge of the 5×4 grid were defined as border with both shoot+root interaction.
plants and were not included in experimental meas- urements. Each PVC tube was placed in a drilled
hole of diameter slightly larger than the PVC tube
2. Methods and materials
Kategori