Forage corn yield and physiological indices under different plant densities and tillage systems

A field experiment was conducted to evaluate the response of forage corn yield to plant densities and tillage systems in northern Iran. In the experiment a split-plot design was used with tillage treatments as main plots and plant density as subplots. The plant density treatments were 90,000. 110,000 and 130,000 plants per hectare, and different tillage systems included conventional tillage (CT), reduced tillage (RT), minimum tillage (MT) and no-tillage (NT). Plant density affected forage dry matter yield, fresh forage yield, stem diameter, leaf area index, crop growth rate, leaf to stem ratio and cob/whole plant ratio. Leaf area index and crop growth rate increased with increasing plant density. The highest dry matter yield was achieved at the highest plant density (16.5 t ha(-1)) and the minimum was obtained at the lowest plant density (14.3 t ha(-1)). Increasing plant density resulted in reduced stem diameter, leaf to stem ratio and cob/whole plant ratio. Tillage systems had significant effects on dry matter yield, fresh forage yield, stem height and number of leaves of forage corn. Conventional tillage and reduced tillage gave similar dry matter yields (17.1 and 16.2 t ha(-1)) that were significantly greater than in the other two tillage systems (MT 14.6 t ha(-1) and NT 13.8 t ha(-1)). Based on the results, the plant density of 130,000 plants ha(-1) using RT system is recommended for forage corn in this area.