EFFECT OF SOIL an‎d FOLIAR APPLICATION OF HUMIC ACID ON GROWTH an‎d PRODUCTIVITY OF SOYBEAN PLANTS GROWN ON A CALCAREOUS SOIL UNDER DIFFERENT LEVELS OF MINERAL FERTILIZERS

A field experiment was carried out on a calcareous soil at Abou massou village (48 km south-west to Alexandria) to determine the effect of humic acid (HA) at the rates of 0 , soil application of (15 kg HA / fed and 30 kg HA/fed) , foliar spray of 0.1% HA and mixture of (15 kg HA/fed as soil application + 0.1% HA as foliar spray along with mineral fertilizers (MF) at the rates of 0 , 75 and 100% of the recommended dose of N, P and K (RDF) on some physical and chemical properties of the studied soil as well as soybean yield and its components. The obtained results indicated that soil application of HA significantly increased soil organic matter content and positively affected bulk density and total porosity (decrease bulk density and increase total porosity). Available N, P and K in soil showed pronounced increases due to the soil application of HA and/ or MF , with a superiority for the treatment of 30 Kg HA + 100% RDF over the other treatments. Growth traits , N, P and K content in seeds as well as seed yield and yield components of Soybean considerably increased as a result of soil or foliar application of HA and/ or MF and the increase progressed with increasing the rate of HA (From 15 kg HA to 30 kg HA/Fed) or MF (From 75 to 100% RDF). The combined application of HA and MF was more prominent in enhancing the aforementioned parameters compared to the treatments received solely application of MF. In this respect, the highest values of these parameters were produced by the combined application of 30 kg HA/fed with 100% RDF.