Evaluating the effect of manual hoeing and chemical weed management practices on the productivity and profitability of dry bean (Phaseolus vulgaris L.) in the south-eastern zone of the DR Congo

The proliferation of weeds in agricultural fields competes directly with crops for essential resources such as, leading to reduced crop yields and economic profitability. The objective of this study was to evaluate the effect of weed management practices on dry bean productivity and economic profitability. Field experiments were conducted between 2018 and 2019 following a Randomized Complete Block Design with four replications and seven treatments. The treatments included: MW (Manual hoe weeding 21DAS), H1 (paraquat 3 l ha⁻¹), H2 (acetochlor 3 l ha⁻¹), H3 (atrazine 3 l ha⁻¹), H1H2 (paraquat 1.5 l ha⁻¹plus acetochlor 1.5 l ha⁻¹), H1H3 (paraquat 1.5 l ha⁻¹ plus atrazine 1.5 l ha⁻¹) and H2H3 (atrazine 1.5 l ha⁻¹ plus acetochlor 1.5 l ha⁻¹). Dry seed yield obtained in 2018 were similar regardless of treatments. However, in 2019, among the herbicides, H1 induced the highest yield (1t ha⁻¹), while the lowest (0.45 t ha⁻¹) was recorded with H2. In addition, the decrease in yield under MW (0.86 t ha⁻¹) was due to the high density of following species: Cynodon dactylon, Commelina benghalensis, Imperata cylindrica, Bidens pilosa, Euphorbia heterophylla and Euphorbia hirta. The economic analysis of treatments using the Ratio Cost Value (RVC > 1) classified them in descending order: MW > H1 > H2H3 > H3 > H1H3 > H2 > H1H2. However, when the cultivated area to be weeded is expanding and labor becomes scarce, the rains are regular and abundant, manual hoeing may become tedious. In this case, the application of 3 l ha⁻¹ of paraquat becomes an alternative to manual hoeing for farmers wishing to increase dry bean seed production.