The objective of this study was to evaluate the profitability of the main food crops in the context of the current government policy of promoting the use by farmers of improved inputs. This study tried to estimate the magnitudes of costs associated with the use of chemical fertilizer on climbing beans, maize, sorghum and soybeans grown in the province of Kigali rural and the benefits farmers would get by investing their labor and money in these crops. In less detail, this study analyzed some recent survey data seeking to put crop production in a wider perspective of the household's limitations and/or opportunities when dealing with the issue of improving crop yields on its land. Data analysis was done at the agroecological zone level and considered the three major agroecological zones of the Kigali rural province, namely, plateau de l'Est zone, plateau central zone and bugesera zone. Of the four crops selected in plateau de l'Est zone, the use of fertilizer would generate returns to family labor equal to or greater than the local agricultural labor wage for maize, soybeans and sorghum. The three crops provide also the best returns to the combination of organic and mineral fertilizer but production intensification by fertilizer use would be financially more attractive for soybeans and sorghum production. In plateau central zone the returns to family labor are greater than the agricultural labor wage for one crop, that is, sorghum grown with "DAP + urea" as mineral fertilizer. However, two crops, sorghum and soybeans, would give enough returns to the combination of organic and mineral fertilizer and their intensification by fertilizer use would be financially attractive. Sorghum was the only crop perceived by previous studies as potentially profitable with fertilizer use in Bugesera zone. The remuneration rate, the returns to family labor and the margins generated with the available data do not support that assumption for the use of NPK but they do for the combination "DAP + urea." The latter improves all the three crop budget analysis criteria, compared to the traditional modes of production. Hence, sorghum would be more profitable in Bugesera zone when grown with "DAP + Urea" as chemical fertilizer.