Impact of water regime and harvest management on the quantity and quality of herbaceous forage in the Sahelian ecosystem of Senegal

Background: The climate and harvest management practices influence forage production in the Sahel. However, the combined effect of these parameters has not been assessed. Aim: This study aims to measure the joint effect of rainfall and harvesting practices on the quantity and quality of forage. Methods: Aboveground biomass samples were collected during (July and August) and at the end (October) of the 2021 rainy season by full cutting on 68 harvest plots: 20 plots with different water regimes (varying water quantities and duration of inputs), and 48 plots with different quantities of water combined with different cutting heights (0 or 5 cm above ground) and harvest periods (early or late). Results: The aboveground biomass ranged from 2,932.2 ± 1,672.1 to 6,383.6 ± 2,962.6 kg/ha for water regime treatments, and 2,397.7 ± 6,263.4 kg/ha to 15,059.2 ± 9,782.9 kg/ha for cumulated harvest aboveground biomass. The crude fiber rate (as % of dry matter) was between 5.5 ± 0.9% and 6.4 ± 1.2%. Digestible crude protein varied between 21.8 ± 67.96% and 67.2 ± 15.8%. Regardless of the quantity of water received, equivalent quantities and qualities of forage (p > 0.05) were produced by the plots that were not harvested until the end of the season and those harvested at the beginning of the development cycle of the forage species. The amount of aboveground biomass produced was the same, independent of the cutting heights (3,535.8 ± 2,953.5 for 0 cm and 4,503.4 ± 3,068.6 kg/ha for 5 cm). On the other hand, the plots harvested at the fruiting stage of the species produced forage composed of young plants in smaller quantities and of good quality. Conclusions: The quantity and quality of herbaceous forage yield at the end of the rainy season were mainly influenced by the phenological stage. Forage resource management programs should favor cutting times and heights that allow optimal ground coverage to reduce the risk of erosion.