effect of using different tillage methods on dryland wheat yield under cold, moderate and semi-warm climatic conditions of kermanshah province

to study the effects of different tillage systems on yield and some characteristic of wheat and also some soil properties in wheat dry land area, six experiments were performed in cold, moderate and semi-warm climatic conditions of kermanshah province in west of iran, in a randomized complete block design with five replications. experimental treatments were consisted of no-tillage, reduced tillage and conventional tillage systems. the highest seed yield was observed in no-tillage (2365 kg ha-1) and reduced tillage (2373 kg ha-1) systems of moderate climate of the second year. the highest economic value was related to no-tillage (24832 thousand rials) and reduced tillage (24316 thousand rials) systems of moderate climate of the second year and no-tillage system of moderate climate of the second year (22753 thousand rials). in all climates and years, no-tillage system with 11.97% (about two times) following by reduced tillage with 11.16% (more than 1.5 times), preserved large soil moisture in comparison to conventional tillage system (6.2%). soil organic carbon was not affected by climate type and experimental years, but general trend of differences indicated that no-tillage and reduced tillage systems (except the second year of warm climate) 1.6 and 1.3% were higher than conventional tillage system. the lowest soil bulk density (1.24) was observed in the conventional tillage system. in general, it could be concluded that conservation tillage systems can supply, more yield and economic returns, as well as conserving more water than conventional tillage and its application is a necessary step toward a sustainable agriculture.