Foliar absorption of nutrients: I

Recently, studies on foliar application have made splendid development in the field of agronomy and in the fertilizer industry. This fact has some important meanings. First, the conception of fertilizer has gradually changed from the original meaning. "Non-root" parts of plants do take up nutrients from spray and other applications. This conception could definitely be proved by the use of radioactive isotopes as the tracer. Many investigations by use of radioactive isotopes, 14C ( 1 and 2 ) 32P (1, 3, 4, 5, 6, 7 and 8) 42K (9 and 10) 45Ca (10) etc. have since been conducted showing the foliar absorption of nutrients. The second important meaning is the improvement of applica tion methods of fertilizers. By the foliar application method, excellent effects which could not be carried out by the soil application method have been displayed. When fertilizers are applied to leaves of plants in critical times as a supplementary fertilizer, they can be absorbed quickly plentifully into plants. Foliar application of micronutrients, for instance, Mg, Fe, Zn, and Mn have been used succesfully to the deficiencies in plants. Among the macronutrients, phosphorus could perhaps offer more promise as a foliar applied fertilizer, because when phosphatic fertilizers are applied to soil, a large percentage of phosphorus usually becomes fixed in unavailable form to growing plants. On the other hand, especially in a high rainfall area, the application of soluble nitrogen fertilizer to the soil has resulted in low efficiency due to leaching loses (19). So, studies on foliar absorption of urea, phosphorus and micro-nutrients have especially been investigated by many workers. In other cases, there are possibilities that fertilizers can be applied to plants with germicides, insecticides, etc.