Influence of velvetleaf (Abutiron theophrasti Medic.) density on the growth and development of corn

Abstract

We examined experimentally the growth of corn and velvetleaf by changing the density of velvetleaf and obtained the following results.
1) We did not observe self-thinning of velvetleaf even at higher densities. At the highest velvetleaf density, 16 velvetleafs per corn plant (71.1 velvetleafs/m²), plant height of velvetleaf changed similarly to that of corn plant (Fig. 2). This suggested that light competition between corn and velvetleaf was intensified under this condition.
2) In the lowest density of velvetleaf, one velvetleaf plant per corn (4.4 velvetleaf/m²), the corn yield decreased about 20% compared to the control. The corn yield also decreased as the density of velvetleaf increased (Table 1).
3) The percentage of dry weight of velvetleaf per total dry weight of corn and velvetleaf had already been determined 40 days after corn sowing (Fig. 3) and seemed to be important in suppressing the growth of velvetleaf in early corn growth. Histograms of plant height overlapped between corn and velvetleaf at high densities (16 velvetleaf plants per corn plant). For low velvetleaf densities (one or four velvetleaf plants per corn plant), growth of velvetleaf was suppressed below the canopy layer of corn in spite of its density (Fig. 4).
4) For higher densities, velvetleaf capsules tended to be located in the upper layer of the community because of the mutual shielding. Therefore, the capsules produced per individual decreased (Table 2). Furthermore, under low-density conditions, the seed production per plant increased though the damage against the corn yield decreased (Table 2).