Prior on-station research showed that sowing dates, sowing density and applications of fungicide and phosphorus (P) increased groundnut (Arachis hypogaea) pod yield by 60–80%. Farmer-managed trials were conducted in the Wa district of the Upper West Region of Ghana from 2004 to 2007 to test the yield response to sowing density, fungicide and P and to assess economic returns of these technologies to farmers. Treatments included: an early maturing groundnut cultivar, Chinese, sown at farmers' density (5–8 plant m−2) without fungicide and without P application (T1, control), with fungicide sprays alone (T2), or with fungicide and P application (T3), cultivar Chinese sown at recommended (higher) density (20 plant m−2) with fungicide and P application (T4), and a full season cultivar, Manipinter, with fungicide and P application (T5). Soil fertility, sowing density, days from sowing to first weeding, incidence and severity of leaf-spot disease and plant population at final harvest were recorded. Relative to farmers' practice, pod yield of cultivar Chinese was significantly increased by 80% with fungicide sprays alone, 108% with fungicide and P application, and 113% with fungicide and P application at higher sowing density. Cultivar Manipinter treated with fungicide and P gave 107% increase in pod yield relative to farmers' practice. Correlation and stepwise regression analyses suggested that major determinants of groundnut pod yield in farmers' fields were plant density, leaf-spot disease and P availability. The increase in yield with fungicide and P application translated into a 4–5-fold increase in gross margin for farmers in the region. Returns to labour and labour productivity were doubled with combined use of fungicide and P fertilizer.