Evaluating the effects cover crops, tillage systems and nitrogen rates on soil properties and sorghum forage yields

Cover crops are considered as a support for sustainable cropping system. Hence، a field study was conducted to examine the effects of cover crops، tillage systems in combination with different nitrogen levels on certain soil properties and sorghum forage yield (cv. KFS3)، at Research Farm University of Tehran، Karaj، during 2004-2005 growing season. Factorial–spilt plot arrangement based on randomized complete blocks design with three replications was applied. A combinations of tillage systems including reduced and conventional with nitrogen rates of 0، 75 and 150 kg ha-1 were assigned to whole plots with rye (Secale cereale) and hairy vetch (Vicia villosa) constituted the subplots. Effect of cover crop prior to sorghum planting was significant on soil bulk density، nitrogen and soil pH، but these effects were not significant on soil organic matter. The effect of tillage systems was only significant on soil pH after harvesting forage sorghum. Soil pH was lower in reduced tillage than conventional tillage. Tillage systems had no significant effect on yield of forage sorghum، but cover crops and nitrogen rates treatments significantly affected forage sorghum. The highest forage yields were obtained from rye and vetch cover crops along with 150 kg N ha-1.