The influence of several soil management systems on the mineral nutrition and production of citrus trees was studied. This study was mode in an experimental orchard installed in 1949 with Hamlin orange on sweet orange (Citrus sinensis Osbeck). Differential treatments were started in 1953. Since 1956 all plots received uniform fertilizer applications and liming. The cultural treatments employed are as follows: clean cultivation with herbicide; clean cultivation plus a cover crop of velvet bean (Stizolobium aterrimum Pip. & Trac.) planted in the spring and cut down in the fall; clean cultivation plus a cover crop of pigeon pea (Cajanus cajan (L.) Millsp.) planted in the spring and cut down in the fall; molasses grass (Melinis minutiflora Béauv.) mulch; and superficial soil plowing. Leaf samples of the spring cycle were collected from each treatment at regular intervals, from October, 1957 to March, 1959, and analysed for N, P, K, Ca, Mg, Fe, and Mn. The seasonal variations in mineral composition of the leaves were studied in relation to the crop harvest in 1958. Grass-mulched plots showed low level of nitrogen in the leaves in comparison with those which did not receive this treatment. Therefore, extra nitrogen fertilizer may be required to prevent competition for nitrogen due to mulching practices in citrus orchards. Mulched plots produced the highest yields every year, followed by clean cultivation plus cover crop of velvet bean, while clean-cultivated plots produced the lowest. Orange yields and leaf phosphorus levels showed similar trends. From this evidence it seems reasonable a preference for cultural practices which enable the trees to accumulate phosphorus. Mulch and lime as dolomitic limestone used together increased calcium and magnesium absorption by trees, so decreasing the probability of a magnesium deficiency os a result of the large amount of potassium made available by the mulch decomposition. I ron and manganese absorption by trees decreased in the mulched plots. The low levels of leaf iron were quite consistent in this treatment throughout the seasons. Clean cultivation plus a cover crop of velvet bean seems to be a promising cultural practice for citrus, regarding the increased orange yields and the low cost of its installation. The economics use of mulch, assuming the amount of grass required, is limited to the cost in obtaining mulching material.