Effects of water deficit and plant interaction on morphological growth parameters and yield of white clover (Trifolium repens L.) and ryegrass (Lolium perenne L.) mixtures
Dw. Lucero et al., Effects of water deficit and plant interaction on morphological growth parameters and yield of white clover (Trifolium repens L.) and ryegrass (Lolium perenne L.) mixtures, EUR J AGRON, 11(3-4), 1999, pp. 167-177
The effects of soil water deficit and interspecific plant interaction were
studied on the dry matter (DM) yield of white clover and ryegrass and on th
e morphogenesis of white clover. Plants were grown either: (1) individually
(no interaction); or in a mixture of equal plant numbers with either (2) j
ust shoot interaction, or (3) both shoot+root interaction. Plants were subj
ected to soil water deficits corresponding to no (0 MPa), moderate (-0.5 MP
a) or severe (-1.0 MPa) water deficit. Ryegrass had higher above- and below
-ground DM yields than white clover. The above- and below-ground DM yield f
or ryegrass, and the above-ground DM yield, stolen growth and relative grow
th rate (RGR), and leaf appearance rate (LAR) for white clover decreased as
soil water deficit increased. In shoot+root interaction at no and moderate
soil water deficit levels, white clover had the highest proportion of abov
e-ground growth in the leaf form (69%) and had, respectively, 11% and 32% m
ore above-ground DM yield than when grown in just shoot interaction; ryegra
ss had, respectively, 20% and 25% more above-ground DM yield than ryegrass
grown in just shoot interaction. In shoot+root interaction at severe soil w
ater deficit, ryegrass had twice as much aboveground DM yield as white clov
er (3.50 g per plant versus 1.59 g per plant, respectively) and white clove
r had 60% less above-ground DM yield than when grown in just shoot interact
ion. In a soil column of restricted depth (30 cm) at no and moderate soil w
ater deficit levels, remarkable increases in shoot biomass yield were obser
ved for both white clover and ryegrass grown in shoot+root interaction. The
increased shoot biomass yield of ryegrass can be attributed to benefits fr
om white clover's N fixing ability, whereas the causes for increased white
clover biomass yield need to be studied further. However, at severe soil wa
ter deficit, ryegrass had a competitive advantage over white clover when gr
own in shoot+root interaction. This was due to the larger root system of ry
egrass and its ability to control transpirational losses more efficiently,
thus prolonging its growth period compared with white clover. (C) 1999 Else
vier Science B.V. All rights reserved.