Morpho – physiological characteristics of Cover crops for analysis of upland rice production in relay intercropping systems

To assess the suitability of Leguminous species in rice intercropping systems, physiological and morphological characteristics of Crotalaria juncea, Cajanus cajan, Mucuna pruriens var. cochinchinensis, Calopogonium mucunoides, Aeschynomene histrix and Stylosanthes hamata were determined in monoculture. C. cajan and S. hamata were selected and intercropped with two upland rice cultivars (WAB56-50, WAB450-24-3-2-P18-HB syn. V4) with different competitive ability, at sowing dates ranging from 0 to 84 days after rice sowing (DARS). In monoculture, C. juncea and C. cajan produced nearly 9 ton dry matter ha-1, whereas the other species produced below half this amount. Total N in leaf materials varied between 25 kg and 70 kg ha-1. Based on relative growth rate of the leaves, the height increase rate and total biomass, C. juncea, C. cajan and M. pruriens were identified as potentially most competitive. In intercropping system, a logistic function was adequate to describe rice grain yield, final rice biomass and legume biomass at one week after rice harvest as a function of legume sowing dates. Differences in rice grain yield were significant (

Modelling assimilation rates of 14 temperate arable weed species as a function of the environment and leaf traits

Information on the response of assimilation rate to environmental factors is lacking for many less competitive weed species that need to be considered in the context of increasing farm biodiversity. A pot experiment was sown to parameterize gross assimilation rate at light saturation and initial light use efficiency for 14 common UK annual weeds and winter wheat at four leaf temperatures. Field experiments were also sown to measure inter-specific differences in specific leaf area (SLA), leaf nitrogen content and assimilation rates in the field at near-optimum temperatures. A generic relationship describing the response of assimilation rate to temperature and light using SLA and leaf nitrogen content as conversion factors successfully predicted inter-specific differences in assimilation rates in the field. This relationship could be incorporated into weed-crop competition models to predict the productivity and competitive impact of weed mixtures, including species outside the current data set. Assimilation rates at light saturation in the field were determined largely by SLA. This trait was variable between species and within a species across the growing season and needs to be well described in mechanistic competition models to accurately calculate instantaneous assimilation rates.Peer reviewe

Analysis of the productivity of upland rice and cover crops in relay intercropping systems using a mechanistic competition model

Relay intercropping systems with rice cultivars (WAB450-24-3-2-P18-HB (V4) and WAB56-50), the competitive Cajanus cajan and the weakly competitive Stylosanthes hamata were evaluated in the tropical savanna zone in Côte d\'Ivoire. The INTERCOM model for competition served for data analysis and understanding of the system based on phenological, physiological and morphological characteristics of the species. Relationships between accumulated legume biomass and yield loss (YL) in rice showed that rice yield was reduced up to 63 % and 100 % by S. hamata and C. cajan respectively, depending on the introduction time. At low levels of YL both legumes performed similarly. At higher levels of rice YL, C. cajan performed better as it produced higher amounts of biomass. Differences in legume biomass at a specified level of rice YL were mainly created in the growth period following rice maturity, which is restricted by water availability. The lesser performance of S. hamata in that period was attributed to the difference in phenology, combined with the short-duration character of the species. The combination of early introduction and short growth duration of this species prevented a rapid leaf canopy development after rice harvest, resulting in the relatively poor biomass production. Options to improve legume biomass production in relay systems should focus on the period following rice maturity.Les systèmes de culture relais avec les variétés de riz (WAB450-24-3-2-P18-HB (V4) et WAB56-50), les espèces compétitives Cajanus cajan et faiblement compétitive Stylosanthes hamata, ont été évalués en zone savane tropicale de Côte d\'Ivoire. Le modèle de compétition INTERCOM a servi à l\'analyse et à la compréhension du système sur la base des caractères phénologiques, physiologiques et morphologiques des espèces. La relation entre la production en biomasse des légumineuses et les pertes en rendement (PR) du riz ont montré que les rendements en riz ont été réduits de 63 % et 100 % par S. hamata et C. cajan, respectivement, en fonction de la date de semis. A de faibles niveaux de PR en riz, les deux espèces de légumineuses se comportent de façon similaire. A des niveaux élevés de PR, C. cajan est plus performant en produisant des quantités de biomasse plus importantes. Les différences de production en biomasse à un niveau spécifié de perte de rendement en riz apparaissent principalement pendant la période suivant la maturité du riz et qui est restreint par la disponibilité en eau. La faible performance de S. hamata pendant cette période est attribuée à la différence de phénologie, associée au caractère cycle court de cette espèce. La combinaison entre le semis précoce et le temps de croissance réduit n\'a pas permis un développement rapide de la canopée après la récolte du riz, entraînant une production relativement mauvaise de la biomasse. Des options pour améliorer la production de biomasse des légumineuses dans les systèmes de culture relais doivent se focaliser sur la période suivant la maturité du riz Keywords: Legumes, cropping systems, yield loss, Côte d\'Ivoire.Agronomie Africaine Vol. 18 (3)006: pp. 285-29