The influence of organic fertilizers,obtained from poplar barks,on the correction of iron chlorosis ofLupinus albus L.

Summary The influence exerted by organic matter on the correction of iron chlorosis inLupinus albus L., grown in calcareous soil, was studied through a pot experiment by incorporating two rates (1.5 per cent and 3 per cent on the soil) of three organic fertilizers obtained from poplar barks. The fertilizers differed in the length of humification process and in the integration with different materials,i.e.: H fertilizer: 8 months humified poplar barks without any addition, HF fertilizer: 4 years humified poplar barks with 4 per cent of metallic iron, HP fertilizer: 18 months humified poplar barks with 25 per cent of poultry manure. The higher rate (3 per cent) of the H fertilizer was the most efficient in reducing chlorosis symptoms and gave the greatest dry matter yield. Among the treatments with the lower rate (1.5 per cent), the HF fertilizer gave the best results; conversely, the HP fertilizer failed to correct chlorosis and to enhance yield. Therefore the experiment suggested that organic fertilizers are useful to correct iron chlorosis, provided their phosphorus content is low and they have undergone a prolonged humification process; furthermore, integration with small amounts of iron leads to a considerable saving of organic fertilizer.