Effect of plant density, organic manure, bio and mineral nitrogen fertilizers on maize growth and yield and soil fertility

Two field experiments were performed at Gemmeiza Agricultural Research Station, Gharbia Governorate, during 2003 and 2004 seasons, to study the effect of three plant densities (16.000, 20000 and 24000 plant/fed.), three treatments of organic manure and biofertilizer(Zero, organic manure and biofertilizer) and four nitrogen fertilizer rates (Zero, 60, 80 and 100kg N/fed.) on growth, yield and yield components of maize besides soil fertility status at harvest. Split plot design with three replicates was used. The results could be summarized as follows : Plant and ear heights of maize plants were significantly increased by increasing plant density in both seasons whereas, area of topmost ear leaf was significantly decreased by increasing plant density in both seasons. Number of grains/row and l00 grain weight were signifcantly decreased due to increasing plant density in the two seasons of study. Grain yield was inc eased significantly in the f irst season while, the ddlerences did not reach the significance level in the second one, as the plant density increased. All of the studied growth characters of maize plants were increased significantly by adding organic manure or treating the seeds with the biofertilizer (mien bin). Moreover, grain yield and its components followed the same trend. Increasing nitrogen fertilizer rate from zero up to 100 kg N/fed. increased significantly the studied maize growth, yield and yield components characters. Increases in maize grain yield/fed. were 80.41, 122.62 and 156.08% with N rates of 60, 80 and 100 kg N /fed, compared with the control treatment, in the first seasons and 32.43, 49.19 and 56.77% in the second one, restively. Maize grain yield was significantly affected due to the interaction of plant densities and Nrates in 2003 season. Moreover, in 2003 and 2004 seasons the organic or interacted with N rates to alter the grain yield character. The treatment of 24000 pla n t/fed. plusmiwnabin plus60 kg N/fed. resulted in the highest value of kg grain;f kg N added (NUE). In addition, the highest value of grain Nuptake was due to the combination of 16000 plank/fed. plus micaobin plus 100 kg N/fed. rate. As for the soil fertility, the combination of 16000 plant/fed. plusmicrobin plus 100 kg N/fed. rate proved to be the must proper in this respect. Nitrogen use efficiency (NUE) increased as the plant density increased. Addition of organic fertilizer or treating the seeds with microbin (biofertilizer) seemed to increase NUE values. Nevertheless, increasing N rate resulted in reduced NUE valueNo. Increasing the plant density slightly decreased the grain Nuptake value while, addition of organic fertilizer or treating the seeds with microbin enhanced such character. Value of grain Nuptake gradually increased due to increasing N rate up to 100 kg N/fed. 8 Values of residual soil N were decreased as plant density increased, while an opposite trend w as observed under addition of organic fertilizer or treating the seeds with microbin. In addition, increasing N rate resulted in gradual increases is such character. Generally, it could be recommended that planting maize at 20000 or 24000 plant / fad and treating maize seeds with microbin as a bio fertilizer and fertilization at the rate of 100 kg N / fad is the most proper combination in order to attain the highest maize grain yield and conserving the soil fertility under Gemmeiza area conditions.