Intercropping of different secondary crops in maize

摘要

Intercropping and bicropping are common cultivation systems in many countries. Maize (Zea mays L.) as a main crop combined with a legume as secondary crop is in general use in many countries. These systems may contribute to a higher biodiversity, and reduced import of fertilizer, concentrates and agrochemicals. The objective of this research was to select an appropriate secondary crop that could be grown with maize in an intercropping system to control weeds while maintaining maize yields. Field beans (Vicia faba L.), crimson clover (Trifolium incarnatum L.), phacelia (Phacelia tanacetifolia Benth.) and thyphon [Brassica rapa L. var. rapa (L.) Thell] were selected as secondary crops. Acceptable yields of dry matter in maize were obtained regardless of secondary crop. Different yield levels were obtained depending on the morphology of the secondary crop. Thyphon, a high, dense secondary crop with large leaves, shaded the lower maize canopy, and thereby reduced the yield of maize. In contrast, field bean, which is tall and has a narrow canopy, did not reduce maize yield. A negative relation was found between the yield of secondary crop plus weeds in August and October and the yield of maize in October. The secondary crops were not sufficiently competitive against weeds in the first part of the growing season. Thyphon competed too much against maize. Field bean and phacelia resulted in a minimum of competition against maize, and a maximum competition against weeds, compared with the other secondary crops.