Accession-Dependent Reproductive Efficiency and Competitive Outcomes Drive System-Level Productivity in Lima bean-Maize Intercropping

Abstract

This study evaluated the growth, yield and competitive dynamics of twenty lima bean (Phaseolus lunatus L) accessions intercropped with maize, alongside sole stands of both crops. The experiment employed a split-plot randomized complete block design, with cropping systems as main plots and lima bean accessions as subplots. Data on plant height, stem diameter, and number of leaves ware collected fortnightly from 4 to 8 weeks after sowing (WAS) for lima bean and up to 10 WAS for maize. Seed yield (t/ha) was determined at harvest. All data were subjected to analysis of variance at α0.05 and intercropping efficiency was quantified using land equivalent ratio (LER), area-time equivalent ratio (ATER), aggressivity index (AI) and competitive ratio (CR). Significant accession effects were observed for all lima bean agronomic traits but cropping system effects were largely non-significant. Despite similar vegetative growth, Lima Purple Small had the highest seed yield (1.360 t/ha) while Erin Ijesha 1 had the lowest (0.353 t/ha). Lima bean exerted strong competitive pressure that was reflected in positive AI and CR>1; with LER and ATER >1 in combinations involving Atisbo Oyo, Erin Ijesha1 and 2, LB50, LB52, B10, B17, Lima Purple Small, Budo Bank Ago Amodu, Tede Oyo, Iju Ekiti and LB51a, except LER˂1 for LB51a; and ATER˂1 for Budo Bank Ago Amodu, Tede Oyo, Iju Ekiti and LB51a. However, maize dominated the remaining eight mixed systems exhibiting positive AI and CR>1 with LER and ATER ˂1 except for LER>1 recorded for systems with Tede Oyo 1, Arugbadegbe, LB51b and Pepelupe Red. Overall, systems with LER and ATER > 1 indicate efficient resource use in space and time. Intercrop with Atisbo Oyo, Erin Ijesha 2 and B10 with highest LER and ATER values and positive AI and CR>1 for lima bean, demonstrated strong competitive balance and system-level productivity and are recommended for adoption.