Drivers of cotton yield response to topping in farmers’ fields in Mali

Manual topping of cotton plants, which involves cutting off the terminal bud at the top of the main stem, has agronomic benefits, such as reducing vegetative exuberance, ensuring earlier production, or increasing yield by producing more bolls per plant. This technique also offers a promising alternative to chemical control by depriving certain pests of resources and triggering the plant's natural defenses. In Mali, though on-station experiments showed that topping did not substantially increase seed cotton yield, many growers have already adopted this technique mainly due to increased production. In the present study, a survey of a network of 200 pairs (topped vs. non-topped) of farmers' cotton plots was performed to verify this statement and to identify the local (cultivation practices and environment) and ecological factors (rainfall, landscape context) that modulate the response of cotton yield to topping. In farmers’ plots, cotton topping contributed to a 25% increase in the seed cotton yield. The yield response to topping increased with the earliness of planting, the cumulative rainfall received after topping, regardless of the planting date, the supply of manure, and the pressure of piercing-sucking insects, which topping significantly reduced. The integration of topping into cotton-growing systems should be associated with other levers to reduce the dependence on chemical inputs, and sociotechnical obstacles should be considered to stimulate the participatory design of new sustainable cotton production strategies.