To reduce poverty and food insecurity in Africa requires raising productivity in agriculture. Systematic use of fertilizer and hybrid seed is a pathway to increased productivity, but adoption of these technologies remains low. We investigate whether the quality of agricultural inputs can help explain low take-up. Testing modern products purchased in local markets, we find that 30% of nutrient is missing in fertilizer, and hybrid maize seed contains less than 50% authentic seeds. We document that such low quality results in negative average returns. If authentic technologies replaced these low-quality products, average returns for smallholder farmers would be over 50%.