-A fractal root model with parameter estimation based on pipe model theory was applied for studying root architecture of Erythrina lanceolata and Gliricidia sepium associated with crops in agroforestry. The results were compared with a theoretical volume-filling fractal model on scaling of plant vascular system. Scaling of root diameter at bifurcation followed same parameter values over the whole root system. The parameter values were approximately equal in both species. Length between two bifurcations could not be estimated according to volumefilling fractal principles, but an empirical regression was used. An empirical model was also applied for estimating bifurcation angles. These characteristics seem to respond strongly to local root environment, and their modelling calls for studying root-soil interactions. Agronomic applications of this study indicate the usefulness of an architectural approach for the study of belowground interactions in agroforestry systems.Erythrina lanceolata / Gliricidia sepium / agroforestry / pipe model / self-similarity Résumé -Application d'un modèle racinaire fractal à l'estimation de la biomasse et de l'architecture racinaire de deux espèces d'arbres légumineux. Un modèle racinaire fractal dont l'estimation des paramètres repose sur la théorie du « modèle vasculaire » a été appliqué à l'étude de l'architecture de Erythrina lanceolata et Gliricidia sepium cultivés dans des systèmes agroforestiers. Ce modèle a été confronté à un modèle fractal théorique dédié à la simulation du système vasculaire de plantes. La diminution de la section conductrice au niveau de chaque ramification demeure indépendante du diamètre, et peut-être considérée comme étant invariable à l'échelle de l'ensemble du système racinaire. Les valeurs des paramètres d'échelle sont approximativement équivalentes pour les deux espèces. La distance entre deux ramifications n'a pas pu être estimée à partir du deuxième modèle, aussi a-t-elle été estimée à partir d'une régression empirique. Un modèle empirique a éga-lement été utilisé pour l'estimation de la distribution des angles de ramifications. Ces modalités sont typiques d'interactions fortes avec les caractéristiques de l'environnement local, et leur modélisation nécessite une étude approfondie des interactions sol-racines. Cette étude débou-che sur des considérations agronomiques qui montrent l'utilité d'approches architecturales pour l'amélioration de la gestion des interactions souterraines dans les systèmes agroforestiers.Erythrina lanceolata / Gliricidia sepium / agroforesterie / modèle vasculaire / autosimilarité
Objective: to determine the effect of increasing rates of Mocap® 6EC (ethoprophos-AMVAC) on grape (Vitis vinifera) own-rooted cv. Flame and cv Red Globe grafted onto Quebranta rootstock Meloidogyne spp. control. Methodology and Results: two field experiments of increasing rates of 0, 6, 8, 10, and 12 L ha-1 of Mocap® 6EC (ethoprophos-AMVAC) using a complete randomized block design with 4 replicates were set up on grape (Vitis vinifera) own-rooted cv. Flame and cv Red Globe grafted onto Quebranta rootstock for Meloidogyne spp. control. To quantify nematode numbers in soil and roots, and the number of galls in a linear meter root, soil and root samples were taken just before treatment and at 30, 60 and 90 days after product application. In both experiments, at 30, 60 and 90 days after the application, a decreasing linear effect on Meloidogyne spp. numbers in soil (P< 0.0001) and roots (P≤ 0.0002) and number of galls (P< 0.0001) was observed as rate increased. The average reduction was of 4.6, 4.9 and 5.2; and 5.5, 6.0 and 6.3 individuals per 100 g of soil, and 5.6, 9.9 and 9.9, and 4.9, 7.7 and 8.2 nematodes per 100 g of roots, and 2.0, 4.0 and 4.3, and 1.8, 3.9 and 4.9 galls per linear meter of root, by every litre of increase on the applied rate, at 30, 60 and 90 days post application, for the experiment at Ica and Lima department, respectively. Differences in biological efficacy among rates were found for soil (P< 0.0001) and root (P< 0.0001) nematode control, and number of root galls (P< 0.0001), increasing the control as the rate increased in both experiments. Efficacy in soil nematode control varied from 51 to 98% and 73 to 99%, in roots it varied from 61 to 85% and 61 to 87%, and in the number of root galls from 55 to 84%, and 58 to 81% for the experiment at Ica and Lima department, respectively. Conclusions and application of findings: All Mocap® 6EC rates tested reduced Meloidogyne spp. in soil and roots, and the number of galls per linear meter of root, with higher reductions as the rate increased. Then the recommended rate is 10-12 L ha-1 incorporated in a drip irrigation of two hours.
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