Performance of Maize/Bean inter-cropping systems under low and medium rainfall situations: disease incidence

Maize/bean cropping system experiments were conducted at Melkassa and Awassa during 1992 cropping season. Two early bean varieties with different growth habits were planted simultaneously with maize and relay planted one month after maize planting in different planting patterns in a randomized complete block design. The objective of the experiments were to evaluate the relationship that exists between maize and beans subjected to different planting patterns and planting schedules to bean varieties in reducing disease incidence and giving sustainable yields under low and medium rainfall situations. At physiological maturity rust infection was observed to be about 2 percent in intercrops whereas about 8 percent infection was observed in sole Awash-1. Similarly, about 4-8 percent infection was observed from physiological maturity. Maize/bean intercropping significantly reduced the incidence of bean rust at Awassa by inhibiting the spread of spores and due to wider spacing between bean plants in 2 rows maize/1 row bean intercrop and maize/bean mixed in the same row patterns. Contrary to this, incidence of anthracnose was higher in intercrops compared to sole beans. At maturity, treatments mixed cropped with Awash-1 and M-142 were infected by about 8-25 percent and 20-25 percent, respectively and their respective sole cultures were infected by about 3 and 5 percent for Awash-1 and M-142, respectively. But when beans were planted in 2 rows maize/1 row bean pattern the incidence was low ranging between 5-10 percent. The increase in incidence of this disease in mixed cropping might have aggravated due to shading from maize plants that created favorable microclimate for spore multiplication and dissemination mostly in broadcast patterns. Both bean varieties planted simultaneously with maize in 2 rows maize/1 row bean intercrop pattern gave significantly higher yield advantage at both locations. Although these advantages were attributed to improved spatial arrangement and temporal difference resulting in better utilization of growth resources which in turn may also have reduced disease incidence in intercropped treatments. Thus, it was concluded that either of the bean varieties planted simultaneously with maize 2 rows maize/1 row bean intercrop pattern could give sustainable yields in addition to reducing disease incidence and also may avoid risk of crop failure in the dryland areas of Ethiopia.