GROWTH, ALLELOPATHY AND WEED MANAGEMENT ATTRIBUTES OF AKIDI COWPEA (Vigna unguiculata (L) WALP.) IN MAIZE CROPPING SYSTEM

Abstract

Weed interference is a major constraint to maize cultivation. Biological control of weeds has been established to be environmentally safe but has not been widely used in maize cropping system. Akidi Cowpea (AC), an underutilised indigenous legume with trailing and vigorous growth, has the attribute to suppress weeds when grown as interplant. Although, AC’s nutritional profile and health benefits have been studied intensively, its growth under different Light Intensities (LI) and allelopathic effect on maize has not been fully established. Therefore, growth under different LI, allelopathy and weed management attributes of AC in maize cropping system were investigated. Akidi cowpea cultivar IT84D-666 (1 seed/pot) was sown in 5 kg pot under four LI: 30% (12396-lux), 50% (20940-lux), 70% (28423-lux) and 100% (40372-lux) in a Completely Randomised Design (CRD) in four replicates. Shoot Dry Weight-SDW (g) and Number of Root Nodules (NRN) were determined at nine Weeks After Sowing (WAS). Shoots and roots of AC were harvested, air-dried and milled into fine powder. Milled samples (144, 72, 36 and 0 g), each of shoots and roots were dissolved in 1 L distilled water to obtain 100, 50, 25 and 0% concentration of Aqueous Shoot Extracts-ASE and Aqueous Root Extracts-ARE. Maize seed (DTMA-Y-STR) was sown in 10 kg pots in screenhouse in a CRD in four replicates. At two WAS and subsequently forthnightly till eight WAS, 300 mL of ASE and ARE were applied to the soil. Plant Height-PH (cm) and SDW at eight WAS were measured. The treatments: maize interplanted with AC at 20,000 (M1), 30,000 (M2), 40,000 (M3) plants/hectare, hoe weeding (M4), weedy check (M5) and Primextra-2.5 L/ha (M6) were evaluated. Treatments were laid in randomised complete block design, each replicated four times. Weed Control Efficiency–WCE (%), maize SDW and Grain Yield–GY (t/ha) were determined at maturity following standard procedures. Data were analysed using descriptive statistics and ANOVA at α0.05. The SDW of AC at 30%-LI (11.3±0.4) and 50%-LI (11.5±0.2) were similar and significantly lower than 70%-LI (13.0±0.3) and 100%-LI (13.8±0.3). The NRN from 70% (41.4±1.1), 100% (43.6±1.0) were similar and significantly higher than 30% (2.7±0.6) and 50% (7.4±1.0). Maize PH ranged from 97.7±1.1 in 100%-ASE to 106.4±0.7 in 25%-ASE. The highest PH of (106.7±0.6) was obtained under 25%-ARE, while 100%-ARE (101.9±0.6) had the least. The highest maize SDW of 31.3±0.7 and 27.0±0.7 were obtained in 100%-ASE and 100%-ARE, respectively. The WCE was highest in M3 (94.8%) and least in M5 (66.4%). Maize SDW was highest in M3 (84.9± 0.7) and least in M5 (30.2±4.2). The GY of maize at M6 (2.0±0.8) was significantly higher than M3 (1.7±0.6), M4 (1.7±0.6), M2 (1.5±0.6), M1 (1.5±0.6) and M5 (0.7±0.3). Light intensities of 70% and 100% enhanced shoot dry weight and number of root nodules of akidi cowpea. Aqueous shoot or root extracts of akidi cowpea at 25% concentration increased maize plant height, while 100% concentration increased dry matter accumulation. Maize and akidi cowpea interplant at 40,000 plants/hectare suppressed weeds and improved maize shoot dry weight.