Grain yield of irrigated winter wheat as affected by stubble-tillage management and seeding rates in central Iran

In central Iran, the straw of previous crop (irrigated wheat) is baled and removed and the stubble is burnt in situ because of the difficulties of plowing in the presence of high volumes of stubble. To recommend a non-burning stubble management to the farmers, it is essential to study the effects of different stubble incorporation methods on the yield of subsequent crops. An experiment was conducted on a silty clay loam soil to determine the effects of different stubble disposal methods on the yield of an irrigated winter wheat (Triticum aestivium L.) cultivar (Ghouds). The experiment was conducted in split-plot design with three replications. Three seeding rates ( 100, 130 and 160 kg ha(-1)) were used as main plots and five stubble-tillage management systems (consisting of leaving wheat stubble on or mixing with the soil surface, incorporating by plowing or stubble burning) were used as split-plots. Treatment effects were compared by measuring yield and yield components. Differences in grain yields among three seeding rates were not significant. The presence of stubble influenced yield, with highest yields were produced after the stubble was burnt. Yields were reduced when stubble was present, especially when it was mixed with the soil surface using a rotovator to a depth of 8 cm. In non-burning stubble disposal methods, incorporation of stubble by plowing to a depth of 25 cm and planting with a broadcasting method had the highest yield. The grain yield was 11% more in direct drilling as compared to the rotovator combined seeding. On this soil, incorporation of the stubble by plowing to a depth of 25 cm and planting with a broadcast seeder is recommended to improve reliability of crop production. (C) 2001 Elsevier Science B.V. All rights reserved.