Impact of Cyanobacteria, Humic Acid and Nitrogen Levels on Maize (Zea Mays L.) Yield and Biological Activity of the Rhizosphere in Sandy Soils

A field trial was conducted in EL-Ismailia Research Station, Agricultural Research Center (ARC), Egypt during two successive summer seasons of 2010 and 2011 on maize crop hybrid single cross 10 to find out the impact of cyanobacteria (CB) and humic acid (HA) forms applied with different methods under three nitrogen fertilizer levels on maize yield and yield attributes, as well as, their effect on the biological activity of the soil around the rhizosphere of maize plants. Results revealed that in both tested seasons, all yield attributes were significantly affected in the first season, whereas, no significant response detected in the second season. The use of either CB or HA accelerated days to 50 % tasseling and silking in the first season, which were earlier than those recorded in the second season. In both tested seasons, the use of CB (dry and spray) along with 120 kg N fed -1 (One hectare = 2.4 feddan) gave significantly maize grain yield that was not significantly different from that recorded by the use of 150 Kg N fed -1 alone (full recommended N dose). Also, the use of either CB or HA increased the soil biological activity of the plants rhizosphere in terms of total count bacteria, carbon dioxide evolution, dehydrogenase activity (DHA) and nitrogenase activity. Generally, the application of CB and HA may result in the reduction for chemical