Agronomic Performance Evaluation of Intercropping Two Common Bean Breeding Lines with a Maize Variety under Two Types of Fertilizer Applications in the Colombian Amazon Region

Intercropping the common bean (Phaseolus vulgaris L.) with maize (Zea mays L.) is a widely used agronomic practice in smallholder farms in different regions of the world. Although it is a common practice in the Colombian Amazon region, crop yields are low due to the degradation of low fertility, acidic soil and high-temperature stress. Studies are needed on how the integration of genetically adapted common bean breeding lines into an intercropping system can benefit smallholders. The objective of this study was to: (i) evaluate differences in agronomic performance of two common bean lines when intercropped with maize in two different patterns under two types of fertilizer applications; and (ii) identify which intercropping pattern is better to maximize productivity and land use in the Colombian Amazon region. To achieve these aims, 2 field experiments (October 2018 to January 2019, season 1; April to June 2019, season 2) were conducted in the Colombian Amazon region. A randomized complete block design (RCBD) with three replications in a nested trifactorial arrangement in a split-plot scheme was used. The experimental design consisted of 2 advanced bean breeding lines of BFS 10 and ALB 121 (main plots); 3 cropping system patterns, including a monoculture, intercropping pattern 1, and intercropping pattern 2 (subplots); and 2 types of fertilizer, inorganic and organic (sub-subplots), for a total of 12 treatments. The experiment was conducted in two growing seasons in low fertility, acidic soil. Different competition indices and monetary advantage index values were estimated depending on the yield and cost of production from maize and bean intercropping patterns (land equivalent ratio, LER; relative crowding coefficient, RCC; aggressiveness index, AI; competitive ratio, CR). A significant effect on grain yield was observed with both intercropping patterns compared to monocropping of beans and maize. Grain yields obtained for maize were similar under monoculture with both types of fertilizer application, while both bean lines yielded better in monoculture under the application of inorganic fertilizer. Under intercropping patterns, the yield reductions were from 8 to 30% for maize and from 43 to 72% for the 2 bean lines. LER values increased with intercropping patterns under both types of fertilization, which was supported by positive values in the actual yield loss index. The interaction indices between the two crop components showed a greater dominance of maize over beans (RCC, AI, CR). However, the intercropping systems increased the economic advantage (the monetary advantage index) over monocropping. Smallholders in the Amazon region can profit through increased grain yield as well as land-use efficiency by integrating a genetically adapted bean breeding line, BFS 10, as an intercrop with maize under the application of organic fertilizer.