Effect of Weed Control Regimes and Spacing on Productivity and Economic Benefit of Groundnut (Arachis hypogaea L.) Production.

Abstract

Two field experiments were conducted at the Multi-purpose Nursery of the Akenten Appiah-Menka University of Skills Training and Entrepreneurial Development (AAMUSTED) in Mampong-Ashanti during the primary and secondary rainy seasons of 2022. The objective was to evaluate the influence of weed management and plant spacing on the phenology, growth, yield, and economic returns of groundnut cultivation. A split-plot design with four replications was employed, where the main plot factor was weed control (WC) with five levels: (i) weed-free (consistent weeding every two weeks), (ii) weeding once at 4 weeks after planting (WAP), (iii) weeding twice at 2 and 6 WAP, (iv) weeding twice at 4 and 8 WAP, and (v) no weeding (control). The subplot factor was plant spacing, tested at three levels: (i) 50 cm x 10 cm, (ii) 50 cm x 20 cm, and (iii) 50 cm x 30 cm. The findings revealed that the treatment of weeding twice at 4 and 8 WAP and a spacing of 50 cm x 20 cm resulted in the earliest 50% emergence and the highest plant establishment rates across both seasons. Regular weeding prompted the earliest 50% flowering and maturity during the primary season, while weeding twice at 4 and 8 WAP led to the earliest 50% flowering during the secondary season. The 50 cm x 10 cm spacing led to the earliest 50% pegging and podding in both seasons, whereas the 50 cm x 20 cm and 50 cm x 30 cm spacings had the shortest duration to pegging and podding. The interaction between weed control and spacing yielded the highest pod counts per plot and the heaviest hundred-seed weight in both seasons. Regular weeding and a spacing of 50 cm x 30 cm resulted in the tallest plants from 30 to 72 days after planting (DAP) in both seasons, while the combination of weeding twice at 4 and 8 WAP and 50 cm x 10 cm spacing produced the shortest plants. Weeding twice at 2 and 6 WAP led to a significantly higher number of branches per plant, and the 50 cm x 30 cm spacing significantly impacted pod weight per plot compared to the other spacings in both seasons. Weeding twice at 2 and 6 WAP and 50 cm x 10 cm spacing produced greater shoot dry weight from 58 to 86 DAP in the secondary season compared to regular weeding and 50 cm x 10 cm spacing. The unweeded control and 50 cm x 10 cm spacing resulted in higher fresh and dry weed weights at 72 DAP for both seasons. The interaction of weed control and spacing showed that the unweeded plot and 50 cm x 30 cm spacing led to greater shoot dry weight from 58 to 86 DAP in the primary season, while weeding once at 4 DAP and 50 cm x 30 cm spacing resulted in greater fresh and dry weed weights in the secondary season. Weeding once at 4 DAP also significantly increased canopy width. Seed yields ranged from 1,602 to 2,292 kg/ha in the primary season and from 1,458 to 2,167 kg/ha in the secondary season. The weed-free and weeding twice at 4 and 8 WAP treatments produced the highest seed yields, which were 43-47% and 34-49% higher than the unweeded treatment, respectively. For optimal profitability in groundnut production, regular weeding (weed-free) with 50 cm x 20 cm spacing is recommended, while weeding twice at 2 and 6 WAP is suitable for both seasons. The weeding twice at 4 and 8 WAP treatment recorded the highest total benefit-cost and net benefit-cost ratios, whereas the unweeded treatment yielded the lowest total benefits.