Researchers conducted field experiments on castor plants in dryland conditions to determine the optimal fertilizer doses for different yield targets. They analyzed soil tests and found that specific amounts of nitrogen, phosphorus, and potassium were needed to achieve desired castor seed yields. The study showed that the nutrient efficiency of the soil and fertilizer varied for each nutrient. By developing fertilizer adjustment equations, the researchers created a tool to help farmers determine the right fertilizer doses based on soil tests for reaching specific castor yield goals in dryland areas.