New crop management strategies like biostimulation could help close yield gaps in established cropping areas affected by climate change. Field foliar application of humic substances (HB) could be implemented as an agricultural practice only after long-term validation at the farm level. On-farm experimentation (OFE) in farmers’ fields can be used as a testing methodology, including determining the technology’s economic profitability. A total of 447 on-farm experimentation trials on soybean, rice, maize, wheat and barley were installed from 2014 to 2023 in the main production zones of Uruguay. In rice, a significant mean increase (7%) independent of the production conditions (soil, climate, variety, and year) was found. In wheat and barley, a mean yield response of 12% over 14 years and 17% over six years was obtained, respectively. For all crops, we found a tendency to increase the response in those sites and years with the least appropriate conditions for cultivation. The probability of exceeding the break-even cost ranged from 79.7 % for wheat to 87.5% for rice. The results show for the first time that a single foliar application of an HB at a crop cycle-critical moment of these five grains can be transferred as a simple, sustainable, and low-cost technology to achieve higher yield and economic returns.