The Effect of Green Manure and Nitrogen Fertilizer on Corn Yield and Growth Indices

In sustainable agriculture، using green manure as an alternative for chemical fertilizers has a high importance. To investigate the response of some corn (Zea mays L.) growth indices to green manure and nitrogen fertilizer an experiment was carried out at the Research Farm of Agricultural and Natural Resources Faculty، Razi University during the 90-91 growing season. The experiment was split plot based on a randomized complete block design with three replications. The main factor was green manure and its incorporation time including rye incorporated in March، rye incorporated in April، common vetch incorporated in March، common vetch incorporated in April، mixed (rye + commom vetch) incorporated in March، mixed incorporated in April and control (no green manure). The sub factor was nitrogen fertilizer as urea with three levels including 0 (no fertilizer)، 200 kg. ha-1 (the 50% of the recommended amount) and 400 kg. ha-1 (the 100% of the recommended amount). Results indicated that the highest corn leaf area index، crop growth rate and grain yield were obtained in common vetch treatment incorporated in April and the lowest ones were recorded in control treatment (without green manure). Moreover، common vetch in both incorporation times led to the highest specific leaf area. However، corn relative growth rate، net assimilation rate and leaf area ratio were not significantly influenced by green manure treatments. Among the nitrogen treatments، the 100% of the recommended dose showed the highest values of the traits under study and unfertilized treatment showed the lowest ones.