Farming systems research for wet-season non-rice upland crops in Cambodia is being conducted with the overall aim of poverty reduction and food security for farmers in the Provinces of Battambang and Kampong Cham. Some of these cash crops exhibit low and variable incomes, especially when grown in the early wet season. Cambodian farmers may borrow money to buy crop inputs and often sell their produce to companies and traders from neighbouring countries, hence they are price takers. Some new crop technologies are evaluated which relate to soil and crop fertility management interacting with climatic factors. The DSSAT crop simulation model is used to predict outcomes from alternative management strategies. Bio-economic analyses are conducted to assess the likely appeal of these technologies to Cambodian farmers in a return-on-investment context. The results show that management to adjust the nitrogen fertility available to corn, the use of rhizobium in soybean, and a delay in planting early-wet-season corn may all show substantial financial benefits. Further research and an associated farmer demonstration program involving local extension officers are recommended.