واكنش سورگوم علوفه اي به گياهان پوششي، سيستم هاي خاك ورزي و كود نيتروژن

Forage Sorghum Response to Cover Crops, Tillage Systems and Nitrogen Fertilizer

A cropping system to be sustainable must be supported by cover crops. A field study was conducted to examine the effects of cover crops and tillage systems as combined with different levels of nitrogen application on yield of forage sorghum cv. KFS3, at the research fami of University of Tehran, Karadj, during 2004-2005 growing seasons. A factorial - spilt plot arrangement based on randomized complete blocks design with four replications was applied. A combination of tillage systems of reduced as well as conventional along with nitrogen fertilizer rates of 0,75 and 150 Kg haʹ1 were assigned to whole plots, while annual winter cover crops of lye (iSecale cereale) and hairy vetch (Vicia villosa) constituted the subplots. Results demonstrated the significant effects of tillage systems on plant height, leaf dry weight plant"1 and leaf to stem ratio at first cutting, however there were no significant effects observed at the second cutting. At either cutting, the effects of N on all evaluated traits were significant and increasing with N. Nitrogen rates of 75 and 150 kg ha*1 just affected plant height, leaf dry weight plant*1, leaf to stem ratio and fresh forage yields at first cutting. For either cutting, cover crops varied significantly in terms of plant height, main stem diameter, stem and leaf dry weight plant"1 as well as dry and fresh forage yields. There were no significant differences observed between two cover crops (rye and hairy vetch) for any of the measured traits. Not all measured traits interactions were significant. In total, in the first cutting, plant height, main stem diameter, stem and leaf dry weight as well as dry and fresh forage yields were higher than those in the second cutting were, however the number of tillers plant*1 was higher at the second cutting. The highest forage yields were obtained from rye and vetch at N rate of 150 Kg ha*1 for either of cuttings. As tillage systems differed not significantly, using cover crops in combination with 150 Kg N ha"1, could be thought of as an appropriate recommendation for production in Karadj region.