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In intercropping systems, plant morphology highly determines the amount of resources captured by each component species. However, morphogenesis of cultivated species has been mainly described in mono-specific growing conditions, although plasticity can occur in multi-specific stands. This paper reports on the variability of the morphogenesis of three pea genotypes grown in pure stands and mixed with wheat. Most morphogenetic parameters of pea were dependent on the genotype. However, there was low variability of pea morphogenesis between sole and mixed stands, except for plant height and branching of the long cycle cultivar., Cereal–legume intercrops represent a promising way of combining high productivity and agriculture sustainability. The benefits of cereal–legume mixtures are highly affected by species morphology and functioning, which determine the balance between competition and complementarity for resource acquisition. Studying species morphogenesis, which controls plant architecture, is therefore of major interest. The morphogenesis of cultivated species has been mainly described in mono-specific growing conditions, although morphogenetic plasticity can occur in multi-specific stands. The aim of the present study was therefore to characterize the variability of the morphogenesis of pea plants grown either in pure stands or mixed with wheat. This was achieved through a field experiment that included three pea cultivars with contrasting earliness (hr and HR type) and branching patterns. Results show that most of the assessed parameters of pea morphogenesis (phenology, branching, final number of vegetative organs and their kinetics of appearance) were mainly dependent on the considered genotype, which highlights the importance of the choice of cultivars in intercropping systems. There was however a low variability of pea morphogenesis between sole and mixed stands except for plant height and branching of the long-cycle cultivar. The information provided in the present study at stand and plant scale can be used to build up structural–functional models. These models can contribute to improving the understanding of the functioning of cereal–legume intercrops and also to the definition of plant ideotypes adapted to the growth in intercrops.

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Cereal-legume intercrops are a promising way to combine high productivity and several ecological benefits in temperate agro-ecosystems. However, the proportion of each species in the mixture at harvest is highly variable. The aim of this study was to test whether the timing of small application of N fertilizer is an effective way of influencing the dynamic interactions between species during crop growth and affecting the percentage of each species in the biomass of the mixture without greatly disturbing N-2 fixation. The influence of timing of nitrogen fertilization in pea-wheat intercrops was studied as regards (i) the dynamics of crop growth, (ii) nitrogen acquisition of each species, (iii) the inhibition and recovery of symbiotic N-2 fixation (SNF) after N application and (iv) final performance (yield, % of wheat. grain protein content). This was assessed in winter pea-wheat (Pisum sativum L-Triticum aestivum L) intercrops in 2007 and 2008 at two locations in France. Whatever the stage of application. N fertilizer tended to increase wheat growth and to decrease pea growth. N fertilization (applied once at different dates from tillering to the end of stem elongation) delayed the decrease in the contribution of wheat to total biomass and maintained the competitive ability of wheat over pea for longer than in unfertilized intercrops. N acquisition dynamics and N sharing between the two species were modified by N fertilization and its timing. Crop conditions at the time of N application (growth and phenology of each species, and their proportions in the intercrop biomass) greatly influenced intercrop response to N fertilization. Partitioning between species of soil and fertilizer N was correlated with the proportion of wheat in the total intercrop biomass observed at the date of N application. Short-term inhibition of nitrates on SNF was shown during the few days after N application, whatever its date. SNF recovery after N applications was observed only until pea flowering, but was prematurely stopped by N fertilization after this stage. The effect of N fertilization on the amount of fixed N-2 at harvest was correlated with pea biomass. N fertilization affects N-2 fixation mainly by affecting crop growth rather than %Ndfa in pea-wheat intercrops. In conclusion, N fertilization could be used as a tool to enhance the contribution of wheat in the intercrop biomass but may reduce the amount of fixed N-2 in the intercrop by decreasing pea biomass. (C) 2010 Elsevier B.V. All rights reserved.

ACI Structural Journal, V. 92, No. 5, September-October 1995. Received April 18, 1994, and reviewed under Institute publication policies. Copyright © 1995, American Concrete Institute. All rights reserved, including the making of copies unless permission is obtained from the copyright proprietors. Pertinent discussion will be published in the July-August 1996 ACI Structural Journal if received by March 1, 1996. Seismic Behavior of Steel-Fiber Reinforced Concrete Interior Beam-Column Joints