The high cost of inputs has been one of the main limitations to crop production among small and medium-sized farmers in the Alto Sertao region of Paraiba, given their low capital and the fact that they are often unable to keep up with technological developments in agriculture due to the low level of investment in their properties. Making agricultural production viable at competitive levels for small and medium-sized producers is a challenge and a contemporary reality and it is up to research institutions and universities, through investment in specific research, to meet this demand. In this context, and given the negative financial impact caused by the purchase of fertilizers, we propose developing this study as a way of providing scientific information to watermelon producers in the Alto Sertao region of Paraiba, thus enabling greater profitability and sustainability for this practice.