Adubação da mamoneira III- experiências com doses crescentes de nitrogênio, fósforo e potássio

From 1957-58 to 1959-60 five experiments were conducted in three localities of the State of Sao Paulo to study the effect of increasing rates of application of N, P, and K on castor beans (Ricinus communis L.). While phosphorus and potash increased considerably the yields in three experiments, the responses to nitrogen were generally small and significant only in one case. The elements studied did not appreciably affect the oil content of the seeds. As an average of the five experiments the hectare yield of seeds was 656 kilograms in the unfertilized plots, but increased to 1,176 kilograms in those which received the smaller rates of the three nutrients and reached 1,650 kilograms where the larger rates of them were applied.